| P a g e By Samantha Hurst (1036655) A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Physiotherapy Johannesburg, 13/5/2024 BREATHING PATTERN DYSFUNCTION AMONGST PATIENTS WITH MEDIAN STERNOTOMY POST HOSPITAL DISCHARGE: A CROSS- SECTIONAL STUDY WITHIN A SOUTH AFRICAN CONTEXT i | P a g e DECLARATION I, Samantha Hurst, declare that this research report is my own work. It is submitted for a degree in the Master of Science in Physiotherapy at the University of the Witwatersrand in Johannesburg, South Africa. This research report has not been submitted before for any degree or examination at this or any other institution. Samantha Hurst Signed in Pretoria on date: 13/5/2024 ii | P a g e DEDICATION “Fear not, for I am with you; be not dismayed, for I am your God; I will strengthen you, I will help you, I will uphold you with my righteous right hand”- Isiah 41:10 To my Yahweh, my constant, thank you for your strength and faithfulness. “Im not interested in whether you’ve stood with the great; I’m interested in whether you’ve sat with the broken”- Sue Fitzmaurice To my patients, you have taught me more than I could ever teach you.The greatest demonstration of patience and courage during affliction. “Love is not affectionate feeling, but a steady wish for the loved person’s ultimate good as far as it can be obtained.- C.S Lewis To my family, thank you for showing and teaching me enduring love. iii | P a g e ABSTRACT Introduction: Patients following cardiac surgery via median sternotomy surgical approach experience a deficit in chest wall expansion and respiratory muscle strength during hospital stay. To date, no study has assessed whether there is a long-term breathing pattern dysfunction (BPD) present in patients following cardiac surgery via median sternotomy surgical approach. Aim: To establish whether patients within the period of three months to one year post cardiac surgery via median sternotomy surgical approach still experience a BPD and, if so, to determine the risk factors to development of such a dysfunction. Methods: A cross-sectional observational study was conducted in a private hospital in Pretoria, South Africa from December 2022 - November 2023. Male and female patients between the age of 18-65 years who underwent an elective cardiac procedure via median sternotomy surgical approach were invited to participate. Participants were assessed once within the period of three months to one year post hospital discharge via questionnaires emailed to them and a telephonic video consultation. Outcome measures used included work- and health-related demographic questionnaires, the Physical Activity Vital Sign (PAVS), the Self-Evaluation of Breathing Questionnaire (SEBQ), The Nijmegen Questionnaire (NQ), the Breath Hold Time (BHT) Test, and the measures of upper and lower chest expansion (CE). Data were evaluated using descriptive and inferential statistics. Statistical significance was set at p<0,05. Results: The study population consisted of 52 participants, of which, most identified as male gender (59,60%, n=31) and underwent coronary artery bypass graft surgery (CABG) (51,90% ,n=27). The median age of participants was 57,00 (IQR 14,00) years and most participants presented with an elevated body mass index (28,90 kg/m², IQR 6,60). Return to work rate was established to have been 61,50% (n=32) with a median return to work time (RTWT) of six (IQR 4,00) weeks. Of the participants who returned to work, the majority (17,30%,n=9) worked in administrative occupations involving prolonged sitting (42,50%, n=17). The majority of participants scored positive in three of the outcome measures (51,90%, n=27) for BPD. A weak negative correlation existed between age and NQ and between age and SEBQ (r=-0.32, p=0,02). There was a weak negative correlation between length of iv | P a g e hospital stay and lower CE (r= -0,30, p=0,03). There were weak positive correlations between PAVS aerobic scores and upper CE (r=0,33, p=0,02) ,lower CE (r=0,39,p<0,01) and BHT (r=0,29,p=0,04). There was a weak negative correlation between PAVS aerobic scores and SEBQ scores (r=-0,30,p=0,03). In terms of predictive values, being identified as male gender reduced the odds of developing a BPD in the psychophysiological dimension by 82%. Participants who underwent the surgery classified as “other” were 21 times more likely to score positive in the psychophysiological dimension of BPD than participants who underwent CABG, valve or mixed CABG and valve surgery. Participants who acquired cardiac complications were 11,67 times more likely to score positive in the psychophysiological dimension of BPD than participants who did not acquire complications or acquired other non-cardiac related complications. The absence of post-operative complications reduced the risk of developing a BPD in the psychophysiological dimension by 77%. Additionally, for every minute a patient partook in weekly aerobic exercise, the odds of developing a BPD in the psychophysiological dimension decreased by 1%. In terms of the biochemical dimension of BPD, participants who returned to work were 4,42 times more likely to score positive for BPD in this dimension. Conclusion: There is a high prevalence of long-term BPD amongst patients who underwent cardiac surgery via median sternotomy surgical approach. Factors found to increase the risk of developing BPD in a multidimensional context include the female gender, the type of surgery (particularly thymectomies and atrial septal defect repairs), cardiac post-operative complications and whether a participant has returned to work. Factors found to reduce the risk of developing BPD include the duration of weekly aerobic exercise and the absence of post-operative complications. v | P a g e ACKNOWLEDGEMENTS I would like to thank the following : •Prof. Ronel Roos, my supervisor. •Janine Blumenau for your advice regarding statistical analysis. •The South African Society of Physiotherapy (SASP) and the Wits Faculty of Health Sciences Medical Research Endowment Fund for their grant contributions. •The patients who were willing to participate in the study. •The cardiothoracic surgeons, physiotherapy practice owners and their teams who allowed me to conduct my study on their patients. •Hospital Management for allowing me to conduct research in their hospital. vi | P a g e CONTENTS LIST OF TABLES ............................................................................................................... viii LIST OF FIGURES ............................................................................................................... ix LIST OF ABBREVIATIONS .................................................................................................. x CHAPTER 1 ......................................................................................................................... 1 1. BACKGROUND AND NEED ......................................................................................... 1 1.1. Introduction ........................................................................................................... 1 1.2. Problem Statement ............................................................................................... 4 1.3. Research Question ............................................................................................... 4 1.4. Aim of the Study.................................................................................................... 4 1.4.1. Objectives of the Study ..................................................................................... 4 1.5. Significance of the Study ..................................................................................... 5 1.6. Justification for the Study .................................................................................... 5 CHAPTER 2 ......................................................................................................................... 6 2: LITERATURE REVIEW ................................................................................................. 6 2.1. Introduction ........................................................................................................... 6 2.3. Median Sternotomy Surgical Approach............................................................. 12 2.4. Breathing Pattern Dysfunction Acute Stages Post Median Sternotomy ......... 18 2.5. Breathing Pattern Dysfunction Long -Term Post Median Sternotomy. ........... 23 2.6. Effect of Long-Term BPD on Return to Work and Functional Performance ... 24 2.7. Conclusion .......................................................................................................... 27 CHAPTER 3 ....................................................................................................................... 28 3. METHODOLOGY ....................................................................................................... 28 3.1. Introduction ......................................................................................................... 28 3.2. Type of Study ...................................................................................................... 28 3.3. Study Participants ............................................................................................... 28 3.4. Variables .............................................................................................................. 29 3.5. Outcome Measures ............................................................................................. 29 3.6. Ethical Considerations ....................................................................................... 33 3.7. Pilot Study ........................................................................................................... 33 3.8.The Main Study .................................................................................................... 37 CHAPTER 4 ....................................................................................................................... 41 4. RESULTS.................................................................................................................... 41 vii | P a g e 4.1. Introduction ......................................................................................................... 41 4.2. Objective 1: Prevalence of BPD ......................................................................... 42 4.3. Objective 2: Work and Health-Related Demographic Profile .......................... 43 4.4. Objective 3: Profile of Physical Activity Level .................................................. 47 4.5. Objective 4: Association and Predictive Qualities of the Independent Variables on the Prevalence of BPD ......................................................................... 47 CHAPTER 5 ....................................................................................................................... 57 5. DISCUSSION .............................................................................................................. 57 5.1. Introduction ......................................................................................................... 57 5.2. Objective 1: Prevalence of BPD ......................................................................... 58 5.3. Objective 2: Work and Health-Related Demographic Profile .......................... 61 5.4. Objective 3: Physical Activity Level Profile ....................................................... 70 CHAPTER 6 ....................................................................................................................... 74 6. CONCLUSIONS, RECOMMENDATIONS AND LIMITATIONS ................................... 74 6.1. Conclusion .......................................................................................................... 74 6.2. Limitations ........................................................................................................... 75 6.3. Recommendations .............................................................................................. 77 REFERENCES ................................................................................................................... 79 APPENDICES..................................................................................................................... 96 Appendix 1: Nijmegen Questionnaire .......................................................................... 96 Appendix 2: Self-Evaluation of Breathing Questionnaire ........................................... 97 Appendix 3: Chest Expansion Measurement .............................................................. 98 Appendix 4: Physical Activity Vital Sign ...................................................................... 99 Appendix 5: Demographic Questionnaire .................................................................. 100 Appendix 6: Clearance obtained through the Human Research Ethics Committee of the University of the Witwatersrand ........................................................................... 102 Appendix 7: Approval of title given from the faculty of Health Sciences Post Graduate Office ........................................................................................................... 104 Appendix 8 : Consent documents signed by surgeons and physiotherapy practice owners. ......................................................................................................................... 105 Appendix 9: Consent documents signed by the hospital CEO. ............................... 111 Appendix 10: Information document: ........................................................................ 113 Appendix 11: Graphic evidence of the video demonstrations ................................. 118 Appendix 12: Turnitin Report ..................................................................................... 119 viii | P a g e LIST OF TABLES Table 2.1: Classifying BPD in terms of breathing pattern (Boulding et al.,2016) ……………8 Table 2.2: A mobilisation protocol following CABG via median sternotomy surgical. approach………………………………………………………………………………..16 Table 3.1: Instrumentation and Outcome Measures ……………………...……………….…..32 Table 3.2: Intra-rater reliability Scores for the CE and BHT …………....….………………….36 Table 3.3: Statistical analysis of the data obtained from the study….………………………...38 Table 4.1: Effect sizes of the main dependent variables relating to BPD in the study..........42 Table 4.2: Breathing Pattern Dysfunction Outcomes…………………………………………...43 Table 4.3: Work and health-related demographics of the study population…………….…...43 Table 4.4: VAS Pain Scores of study participants during coughing and deep breathing..…46 Table 4.5: Occupation types of the study population ….…………………………………..….46 Table 4.6: Spearman’s correlations between age and BPD dimensions …………………….47 Table 4.7: Spearman’s correlations between level of education and BPD dimensions. …...48 Table 4.8: Spearman’s correlations between income bracket and BPD dimensions……….48 Table 4.9: Spearman’s correlations between return-to-work time and BPD dimensions. .....49 Table 4.10: Spearman’s correlations between BMI and BPD dimensions…..…...…………..49 Table 4.11: Spearman’s correlations between length of hospital stay and BPD dimensions …………………………………………………………………………………...….........................50 Table 4.12: Spearman’s correlations between pain levels and BPD dimensions……………50 Table 4.13: Spearman’s correlations physical activity vital sign (PAVS) and BPD dimensions.…………………………………………...……………………………………….........51 Table 4.14: Significance of interaction between the independent variables and the dimensions of BPD…………………………………………..…………………………………..... 52 Table 4.15: Logistic regression analyses showing the interaction between the independent variables and the psychophysiological dimension of BPD………………………………......…55 Table 4.16: Logistic regression analyses showing the interaction between return-to-work rate and the biochemical dimension of BPD………………………………………..……...…… 55 ix | P a g e LIST OF FIGURES Figure 2.1 Physiological process relating to the development of BPD……………...…… 10 Figure 2.2 Typical presentation of a patient in the acute stages post-operative median sternotomy as described by Wynne & Botti, (2004)………………………...…. 18 Figure 2.3 Typical alterations seen in pulmonary function tests in the acute stages post operative median sternotomy…………………………………………………… 21 Figure 4.1 A flow diagram illustrating the number of participants reviewed for the study from recruitment to completion and feedback…………………………………. 41 Figure 4.2 A pie chart illustrating the type of surgery requiring a median sternotomy surgical approach……………………………………………….……………….… 45 Figure 5 Tape measure placement to assess CE…………………………….…………… 98 x | P a g e LIST OF ABBREVIATIONS BHT -Breath Hold Time BMI -Body Mass Index BPD -Breathing Pattern Dysfunction CE -Chest Expansion COPD -Chronic Obstructive Pulmonary Disease CABG -Coronary Artery Bypass Grafting FEV1 -Forced Expiratory Volume in One Second FVC -Forced Vital Capacity ICU -Intensive Care Unit NQ -Nijmegen Questionnaire PAVS -Physical Activity Vital Sign RTWT -Return to Work Time SEBQ -Self Evaluation of Breathing Questionnaire VAS -Visual Analogue Scale VC -Vital Capacity 1 | P a g e CHAPTER 1 This chapter serves as an introduction to establish the need and rationale for the study. 1. BACKGROUND AND NEED 1.1. INTRODUCTION Breathing pattern dysfunction (BPD) can be broadly defined as a disruption in overall health due to an abnormal pattern of breathing (Courtney, Greenwood, et al., 2011). The precise definition is unclear as it is an umbrella-concept describing various breathing pattern disturbances for example, hyperventilation syndrome, paradoxical breathing, and upper chest breathing (Vidotto et al., 2019). Breathing pattern dysfunction can be classified into “primary dysfunctional breathing” referring to a non-pathological cause such as anxiety while “secondary dysfunctional breathing” refers to an underlying cardiopulmonary or neurological cause (Vidotto et al., 2019). Currently, there are no gold standard diagnostic tools to define BPD and it is suggested that a multidimensional approach should be used incorporating biomechanical, biochemical, and psychophysiological dimensions when assessing this phenomenon (Courtney, 2011). Biomechanical refers to the actual mechanics of breathing encompassing the movements of the joints of the rib cage and respiratory muscle activity creating a specific breathing pattern (Kiesel et al., 2017). The biomechanical dimension can be assessed by outcome measures such as the Hi Lo test, manual assessment of respiratory motion, rib palpation and measurement of chest wall expansion (Bradley & Esformes, 2014; Tukanova et al., 2020). Biochemical refers to the assessment of an arterial blood gas including pH., carbon dioxide and oxygen levels in the blood (Courtney, Greenwood, et al., 2011; Kiesel et al., 2017). The biochemical dimension can be assessed using capnometry or, a cheaper alternative, that being the Breath Hold Time (BHT) test (Boulding et al., 2016; Courtney et al., 2011). Psychophysiological refers to the body’s ability, or inability, to adapt to changes in the demands of breathing which can result in generalised symptoms (Kiesel et al., 2017). This can be assessed with questionnaires such as the Hospital Anxiety and Depression Scale, the Nijmegen Questionnaire, and the Self-Evaluation of Breathing Questionnaire (Boulding et al., 2016). A median sternotomy is considered the gold standard of approach amongst cardiothoracic surgeons performing procedures such as coronary artery bypass grafting (CABG), valve 2 | P a g e replacements and heart transplants. It allows access to the mediastinum and pleural cavities of the thorax via a vertical incision through the sternum dividing the bone into two halves (Reser et al., 2015). It is noted in the literature that when individuals undergo cardiac surgery via median sternotomy surgical approach, they often present with pulmonary dysfunction post- operatively due to the surgical trauma inflicted onto the thoracic wall thereby affecting chest wall compliance creating an inability to take deep breaths (Urell et al., 2012). This leads to alterations in breathing patterns as confirmed by de Sousa et al. (2016) who concluded that the main characteristics of secondary BPD in the acute stages (within 48 hours post- operatively) include changes in the depth of breathing with a more upper chest breathing pattern, pursed-lip breathing, altered chest expansion (CE) and prolonged exhalation. Gissing (2020) noted a significant change in patients’ chest expansion findings from the pre- to post-operative period in a local cohort of patients who underwent median sternotomy procedures. Findings of Gissing’s (2020) study could be explained partially due to the significant reductions in the respiratory muscle strength observed in the study participants from their pre- to post-operative period. When reviewing change in lung function, Katiyar et al. (2021) found that there was a mean reduction of 36% and 32% with regards to forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) respectively amongst patients who underwent median sternotomy surgical approach. These measures (FEV1 and FVC) was found to closely correlate with reduced measures of upper CE (Roncada et al.,2015). The reduction in lung function parameters post-operatively might be due to pulmonary abnormalities such as atelectasis and intra-pleural abnormalities e.g., pleural effusions as highlighted by Gissing (2020) in a South African cohort. Previous studies found that high risk groups associated with post-operative pulmonary complications such as pleural effusions include advanced age (Wang et al., 2014), female gender (Bechtel & Huffmyer, 2020) and abnormal body mass index (BMI) (>35kg/m² or <18.535kg/m²) (Gao et al., 2016). Literature suggests that the average return to work time (RTWT) for patients who underwent CABG or aortic valve replacement via median sternotomy surgical approach is 30 weeks (±7.5 months). Factors found to delay return to work include older age, female gender, previous diagnosis of depression, low income, and lower education levels (Mortensen et al., 2021). Furthermore, deficits in lung function tests seen in the acute period post-operatively have also been identified after RTWT and these deficits may play a role in delaying or limiting full re-integration into the work force and/or performance in activities of daily living 3 | P a g e (Westerdahl et al., 2003, 2016). Previous studies identified that risk factors associated with reduced performance in lung function tests include valve repair type surgeries, higher pain levels post-operatively and increased length of intensive care unit (ICU) stay (Urell et al., 2012). Westerdahl et al. (2016) in the population of interest outlines the extent of the lung function abnormality over a prolonged period of time, that being one year. Their study showed that pulmonary function measured as vital capacity (VC), FVC, FEV1, FEV1/FVC, peak expiratory flow (PEF), and functional residual capacity (FRC), were significantly reduced compared to pre-operative values (2-5% impairment). Furthermore, within this patient population, Kristjánsdóttir et al. (2004) found an overall restrictive upper chest breathing pattern at three months post-operatively which was yet to be resolved at 12 months following hospital discharge. Due to the dual role of the diaphragm for ventilation and postural control, disruption of ventilation in the form of BPD can lead to a disruption in postural control (Hodges et al., 2007). Activities performed in daily life such as walking, standing, and handling of objects require a degree of postural control to maintain an upright stance. This translates into the ability to execute tasks in the home and workplace environment particularly for patients who perform multitasking such as carrying e.g., files, walking and talking all at the same time (Haddad et al., 2013). Bradley & Esformes (2014), in their study population of healthy individuals, identified a significant association of the biomechanical (measured using Hi Lo test) and biochemical (measured using capnometry) dimensions of BPD with the Functional Movement Screen (FMS). The authors concluded that participants with diaphragmatic or basal breathing patterns have a higher FMS score than those with apical or “upper chest breathing” further confirming the dual role of respiratory muscles in postural control. The above-mentioned studies have identified that there is a prolonged deficit in pulmonary function amongst this population group post discharge from hospital which needs further therapeutic intervention. However, no study has assessed whether there is a long-term BPD (involving assessment of biomechanical, biochemical, and psychophysiological dimensions) following cardiac surgery via median sternotomy surgical approach. Furthermore, no study has established how BPD affects, or is affected, by physical activity level and RTWT in this population group. Westerdahl et al. (2016) also describes a need to establish risk factors associated with long-term pulmonary function deficits post cardiac surgery. This leaves gaps in knowledge on which this study is based. 4 | P a g e 1.2. PROBLEM STATEMENT As stated above, Gissing (2020) established an alteration in CE and muscle strength (biomechanical dimension of BPD) in the acute phase amongst patients who had undergone cardiac surgery via median sternotomy surgical approach. In South Africa, to date, there is no literature on whether there is a long-term BPD amongst this patient population Furthermore, no study has taken into consideration how health and work related demographics (particularly return to work rate and time) may influence or be influenced by the biomechanical, biochemical, and psychophysiological dimensions of the dysfunction. Also, there are no established risk factors predisposing patients who underwent cardiac surgery via median sternotomy surgical approach to development of a long-term BPD. 1.3. RESEARCH QUESTION Do patients within the period of three months to one year post cardiac surgery via median sternotomy surgical approach still experience a BPD? 1.4. AIM OF THE STUDY To establish whether patients within the period of three months to one year post cardiac surgery via median sternotomy surgical approach still experience a BPD and, if so, to determine the risk factors to development of such a dysfunction. 1.4.1. Objectives of the Study The specific objectives of the study were: 1) To determine the prevalence of BPD of patients within the period of three months to one year post cardiac surgery via median sternotomy surgical approach using CE measurements, BHT test and psychophysiological questionnaires. 2)To determine the work (return to work time, type of work, level of education, income bracket) and health-related (BMI, previous diagnosis of depression, length of hospital stay, pain levels as measured using the Visual Analogue Scale, post-operative complications) demographics of patients within the period of three months to one year post cardiac surgery via median sternotomy surgical approach. 3)To determine the physical activity level of patients within the period of three months to one year post cardiac surgery via median sternotomy surgical approach. 4)To determine the association as well as predictive qualities of work and health related demographics and physical activity level on the prevalence of BPD amongst patients within 5 | P a g e the period of three months to one year post cardiac surgery via median sternotomy surgical approach. 1.5. SIGNIFICANCE OF THE STUDY This study may improve our knowledge on whether there is a long-term BPD amongst patients who underwent cardiac surgery via median sternotomy surgical approach. A greater understanding will contribute to early identification and implementation of therapeutic treatment strategies. This study may also identify risk factors predisposing this patient population to development of a long-term BPD further allowing early identification and treatment. 1.6. JUSTIFICATION FOR THE STUDY To date, within the context of South Africa and globally, there is no literature on whether there is a long-term BPD amongst patients who underwent cardiac surgery via median sternotomy surgical approach. Furthermore, no study has taken into consideration how work and health related demographics may influence or be influenced by the biomechanical, biochemical, and psychophysiological dimensions of the dysfunction. This emphasises the importance of conducting such a study as it may aid clinicians in better understanding the multidimensional nature of BPD within the context of their patients’ functional and vocational limitations. Furthermore, a greater understanding and holistic assessment may aid in an improved treatment strategy. The results may be used by clinicians to identify if there is a greater need of long-term follow-up regarding identification of BPD amongst this patient population as well as to identify the patients who are at a higher risk of developing BPD. Chapter 2 consists of a review of the literature to familiarise the reader with regards to the concept of BPD; cardiac surgery via median sternotomy surgical approach and the conventional physiotherapy treatment involved; the presence of BPD in the acute stages post-operative median sternotomy, as well as the effect of long-term BPD on return to work and level of function in this patient population. 6 | P a g e CHAPTER 2 2: LITERATURE REVIEW 2.1. INTRODUCTION The following databases were utilised to collect information included in this literature review: Google Scholar, PubMed, EBSCO host, ScienceDirect and Research Gate. Keywords utilised during the search strategy included: “breathing pattern dysfunction”,” “median sternotomy”, “prevalence South Africa”, “physiotherapy AND median sternotomy”, “long-term breathing pattern dysfunction”, “diaphragm and postural control”. Additional search terms used included: “secondary breathing pattern dysfunction”, “hyperventilation syndrome”, “dysfunctional breathing”, “functional breathing disorder”, “disproportionate breathlessness”, “behavioural breathlessness”, “psychogenic breathlessness”, “functional breathing pattern dysfunction”, “structural breathing pattern dysfunction”, “classification”, “dimensions of breathing pattern dysfunction”, “signs and symptoms”,” upper chest breathing”, “shoulder breathing”, “breathing mechanics”, “post- operative median sternotomy”, “post-operative complications”, “cardiac surgery”, “pre- operative physiotherapy”, “post-operative physiotherapy”, “sternal precautions”, “acute stages median sternotomy”, “lung volume”, “ hypoxemia”, “mobilisation”, “pain management”, ,return to work time”, “risk factors”, “balance”, “functional status”. The literature obtained from the sources described above is discussed under the following headings to provide background to the study: 2.2. Breathing pattern dysfunction. 2.3. Median sternotomy surgical approach. 2.4. Breathing pattern dysfunction acute stages post median sternotomy. 2.5 Breathing pattern dysfunction long-term post median sternotomy. 2.6. Effect of long-term BPD on return to work and functional performance. 7 | P a g e 2.2. BREATHING PATTERN DYSFUNCTION 2.2.1. Dysfunction, not disease Breathing pattern dysfunction is considered by Magarian (1982, p.733) as a “diagnosis begging for recognition”. As the name suggests, BPD is described as a disorder/dysfunction and not a disease (Boulding et al., 2016). Even though it may co-exist with an underlying pulmonary or neurological disease such as that seen with asthma patients (secondary BPD), it has no underlying organic disease process or related pathology (Clifton Smith & Rowley, 2011). It can therefore be more accurately considered an “adaptation” of the body in response to a physical or psychological stressor (Chaitow et al., 2013). This, however, does not mean that the effects of BPD on a patients’ overall health and quality of life should be under-estimated as BPD has influences on various aspects of the body’s physiological processes i.e., emotion, circulation, digestion, and musculoskeletal function (Bradley & Esformes, 2014). Furthermore, it can cause deficits in body biochemistry to the extent that it can mimic other diseases including, pseudo-asthma, irritable bowel syndrome and pseudo-angina (Chaitow et al., 2013). 2.2.2. Prevalence of BPD Breathing pattern dysfunction is frequently under diagnosed amongst various patient populations and is suggested to be as high as 5-11% amongst the general population (Courtney, 2009). Kiesel et al. (2017) argues that it has an even higher prevalence of 50- 80% amongst adults. Regarding specific patient populations, it has been approximated to occur in 34% of those suffering with asthma (Boulding et al., 2016). It also occurs more often amongst women than men with a 14% prevalence in women compared to a mere 2% seen in men regarding an asthma study conducted by Thomas et al. (2005). In the post-operative cardiac surgery population, it was found that 23,5% of patients exhibit an altered breathing pattern post-operatively which was deemed ineffective in catering for the physiological demands of the healing body (de Sousa et al., 2016). The underrepresentation of the prevalence of BPD is suggested to be partly due to a misunderstanding amongst health care professionals about the causes, diagnosis and treatment of this condition which stems from a lack of research regarding the subject (Vidotto et al., 2019). Furthermore, without gold standard methods of testing for BPD, prevalence of this disorder will always be underrepresented (Boulding et al., 2016; Vidotto et al., 2019) and this additionally puts patients at risk of misdiagnosis with deprivation of effective therapies (Barker & Everard, 2015). 8 | P a g e 2.2.3. Classification of BPD As previously stated, BPD can be broadly defined as a disruption in overall health due to an abnormal pattern of breathing (Courtney, Greenwood, et al., 2011). In the past, it has also been referred to as “hyperventilation syndrome”, “functional breathing disorder”, “disproportionate breathlessness”, “dysfunctional breathing” and “behavioural or psychogenic breathlessness” (Barker & Everard, 2015; Boulding et al., 2016). Breathing pattern dysfunction has a widespread spectrum with hyperventilation being the most extreme on the scale and normal breathing being on the other end making it generally difficult to identify when the dysfunction is on the lower end of the spectrum (Osborne et al., 2000). Boulding et al. (2016) states that BPD can occur either in the absence of, or because of an underlying respiratory or cardiac disease. Therefore, BPD can be further classified as “primary BPD” which describes dysfunctional breathing with non-pathological causes such as anxiety and “secondary BPD” which is a physiological response to an underlying cardiopulmonary or neurological disease. Therefore, possible BPD post median sternotomy will be described as “secondary BPD”(Vidotto et al., 2019). Depiazzi & Everard, (2016) proposed another type of categorization where BPD is classified into “functional” describing alterations in pattern of breathing in reaction to another problem such as stress(Mahut et al., 2014), while “structural” denotes to changes in breathing pattern in response to a physical impairment which can be surgically repaired (Nielsen et al., 2013). The “functional” and “structural “classifications can be further subclassified into “thoracic” (involving structures relating directly to the thorax) and “extra thoracic” (involving conditions affecting the upper airway) (Depiazzi & Everard, 2016). Therefore, in this instance, a BPD seen after cardiac surgery via median sternotomy surgical approach can be classified as thoracic functional BPD. Boulding et al. (2016) proposed a classification system to describe the various types of dysfunctional breathing patterns. Table 2.1: Classifying BPD in terms of breathing pattern (Boulding et al.,2016). Breathing Pattern Description Hyperventilation syndrome Described as increased ventilation or respiratory rate and can be further subclassified into: 1) Exercised-induced hyperventilation (dyspnea during aerobic exercise with associated chest discomfort in the absence of bronchospasm thus distinguishing it from exercise-induced asthma). 9 | P a g e 2) Postural hyperventilation (dyspnea with postural changes from a supine position to a standing position). (M. Thomas et al., 2001) Periodic deep sighing Described as frequent sighing (up to 15 times within a 15-minute period) in combination with dyspnea (Prys-Picard et al., 2006). Thoracic dominant breathing Also known as apical breathing, when an individual utilizes a more upper thoracic movement during inhalation with a diminished lateral thoracic or “bucket-handle” movement. This occurs often in patients suffering from cardiac or respiratory disease or those with reduced abdominal compliance as seen in abdominal obesity or ascites. This however may have an absence of underlying pathology and is then termed “dysfunctional”( Courtney, Van Dixhoorn, et al., 2011). Forced abdominal expansion Seen particularly in patients suffering from chronic obstructive pulmonary disease (COPD) where excessive abdominal contraction during exhalation is observed. As these patients usually experience a resistance with exhalation (due to the increased compliance and collapsible nature of the airways), this is considered a normal physiologic adaptation. However, like in thoracic dominant breathing, is termed “dysfunctional” in the absence of underlying pathology (Bianchi et al., 2004). Thoraco- abdominal asynchrony Also termed “paradoxical breathing” is described as an incoordination in movement of the rib cage in relation to the abdomen, therefore the abdomen expands outwards during exhalation and inwards during inhalation. This is seen when there is an upper airway obstruction, neuromuscular weakness or in the case of respiratory distress. Again, it is described as “dysfunctional” in the absence of these pathologies (Upton et al., 2012). As described later in this chapter by Ragnarsdὁttir et al. (2004), an apical breathing pattern is seen post-operatively amongst patients who underwent cardiac surgery via median sternotomy surgical approach and thus the classification amongst this population would be thoracic dominant breathing. 2.2.4. Signs and Symptoms of BPD Individuals with BPD can present with a variety of signs and symptoms. These symptoms include dyspnea; anxiety; exhaustion; light and sound sensitivity; dizziness; tingling in peripheries; muscle cramps; muscle weakness; pain in shoulders, head, and neck. Signs include apical breathing pattern; tachycardia; cardiac arrhythmia; sweating and 10 | P a g e hyperventilation causing respiratory alkalosis (CliftonSmith & Rowley, 2011a; McLaughlin et al., 2011). Figure 2.1 outlines the suggested process related to the development of BPD. Figure 2.1: Physiological process relating to the development of BPD (Chaitow et al., 2013) Breathing Pattern dysfunction may stem from a prolonged state of sympathetic activation or arousal (Courtney, 2011). Thus, the patient may exhibit symptoms pertaining to “fight and flight” physiological reactions (Barker & Everard, 2015). This means that BPD can be a 11 | P a g e symptom of a deeper psychological stress-related problem. Literature concerning battle fatigued soldiers indicated a high prevalence of breathing and cardiovascular problems relating to mental and physical exhaustion following high levels of stress (Courtney, 2011). Interestingly, it has been identified that children and adolescents who exhibit a BPD are often those who are highly driven, perfectionistic individuals who place themselves under excessive amounts of stress to achieve (Barker & Everard, 2015). Amongst the population of patients who underwent cardiac surgery, studies have shown a 15-33% prevalence of depression and anxiety post-operatively (Correa-Rodríguez et al., 2020). Even though these periods of high levels of stress may be periodic, patients fail to return to normal baseline breathing patterns even after the cessation of the stress evoking stimulus has occurred (Courtney, 2009). Thus, BPD can be further defined as breathing which does not adequately balance the states (parasympathetic or “rest and relax” and sympathetic or “fight -or-flight”) of the autonomic nervous system leading to a sympathetic nervous system dominance. In terms of patients post median sternotomy, emotional stress and/or perioperative pain can also lead to a state of sympathetic arousal contributing to a BPD (Courtney, 2011). A constant sympathetic “fight-or-flight” state evokes further anxiety, changes in muscle tone and a lower pain threshold along with other central and peripheral nervous system symptoms (Sueda et al., 2004). When ventilation is inadequate, accessory respiratory muscles of the upper thoracic cage such as the sternocleidomastoid, scalene and upper fibers of trapezius overcompensate for reduced diaphragm movement resulting in increased vertical displacement of the thoracic cage. This associated shoulder elevation gives a very distinct apical “shoulder breathing” or “upper chest breathing” pattern (Courtney, 2009). The over-use of apical muscles during breathing at rest leads to loss of thoracic mobility and alteration of posture. This further plays a role in limiting diaphragm movement as patients most commonly present with an increased thoracic kyphosis posture and a “poking-chin” position of the cervical spine (CliftonSmith & Rowley, 2011). Zafar et al. (2018) further explained that a deviation of cervical and thoracic spine posture has an almost immediate effect on diaphragm strength and movement thus further promoting shallow breathing. It is important to note that patients with restrictive lung pathologies and end stage COPD display an apical breathing pattern as the best way to compensate for their deficits in lung function (Courtney & van Dixhoorn, 2013). With inadequate ventilation, despite treatment for, or exclusion of other underlying causes, there is no surprise that the key symptom of BPD is feelings of being breathless or dyspnea (sensation of increased work of breathing) (Boulding et al., 2016). Multiple mechanisms contribute to an individual’s perception of dyspnea involving receptors located on the 12 | P a g e respiratory muscles, lungs, carotid bodies and brainstem coupled with anxiety which further heightens the perception of dyspnea (Barker & Everard, 2015). Ghannouchi et al. (2016) in their systematic review identified that patients suffering from changes in breathing patterns particularly those seen in COPD and obstructive sleep apnea experience a higher risk of aspiration pneumonia due to the development of swallowing impairment (oropharyngeal dysphagia). Oropharyngeal dysphagia can be caused by multiple factors including the fact that these patient populations have an increased risk of suffering from gastroesophageal reflux (GORD) which can easily cause aspiration (Terada et al., 2010). Patients also show less swallow action during expiration and an increased swallow action during inspiration or during the inspiration-to-expiration transition (swallow-ventilation incoordination). This information should be taken with caution due to the authors (Ghannouchi et al., 2016) identifying a small number of studies (n=28) with absence of randomized controlled trials. Amongst 182 patients post cardiac surgery, Plowman et al., (2023), established that post-extubation, only 11 participants (6%) were classified as safe swallowers while 118 participants (65%) were classified as penetrators to the level of the true vocal folds and a further 53 (29%) were classified as aspirators. The authors further identified that the altered pattern of breathing could be a contributing factor to the ventilation- swallow incoordination. In the section to follow, information regarding a median sternotomy will be provided to better understand how it might link to the development of BPD in patients following such surgery. 2.3. MEDIAN STERNOTOMY SURGICAL APPROACH 2.3.1. Description of Procedure A median sternotomy amongst the adult population is the most common approach for various surgical procedures including CABG, cardiac valve surgery (in the presence of stenosis or regurgitation), transplants and resection of mediastinal tumors amongst others (Mohan, 2017). It is a beneficial surgical technique in that it provides direct access to all important mediastinal structures, however, an additional thoracotomy may be required in the case where exposure to the pleural spaces is necessary (Mohan, 2017; Senst et al., 2021). The approach can be described as a surgical incision made from the midpoint of the manubrium just below the sternal notch of the sternum down to the tip of xiphoid process. After division of subcutaneous tissue, a sternal saw is used to split the sternal bone in two halves to gain access to the thorax (Mohan, 2017; Reser et al., 2015). Once the pericardial sac is opened, the structures of interest are identified, and the appropriate procedure is 13 | P a g e executed e.g., grafts are harvested from other areas in the body and connected to the coronaries in the case of a CABG or a damaged valve is replaced or repaired. After completion of surgery, the thorax is closed, and the sternum is repaired using surgical wires. Pleural and mediastinal drains are left post-operatively for the first few days (Senst et al., 2021). The patient is mechanically ventilated during the procedure to artificially control their breathing and is then extubated within the next 24-48 hours post-operatively in the absence of complications (Knapik et al., 2011). Engelman et al. (2019) further adds that to avoid complications associated with prolonged mechanical ventilation, it is safe for patients to be extubated within six hours of arrival in the ICU. 2.3.2. Prevalence of Median Sternotomy in South Africa In terms of the type of surgery, the most recent statistical analysis amongst patients undergoing cardiac surgeries in a South African context done by the Chris Barnard division of Cardiothoracic Surgery showed that statistics remained constant in terms of CABG (34%), valve replacement (43%) and mixed procedures (8%) over a period from 2003-2014 (University of Cape Town, 2014). They further stated that the need for CABG represents the impact of urbanized lifestyles on the population involving higher incidence of smoking, westernized diet, and stress (University of Cape Town, 2014). This data is unfortunately outdated but it gives an idea of proportions of surgical interventions requiring median sternotomy within a South African context. A more recent study by Reiche et al. (2021) indicating the overall prevalence of cardiac surgery showed a growing number of coronary artery disease in low- and middle-income countries such as South Africa with CABG to be considered the most beneficial surgical intervention. Their retrospective review was done amongst patients who underwent CABG surgery at a tertiary academic South African hospital from 2000-2017. A total of 1218 patients were included in the statistical analysis (case count was generally under 100 annually) and the mean age of patients was 60 (± 10.1) years. All patients had a median sternotomy surgical approach relevant to the study on which this literature review is based. With the growing trend of coronary artery disease (University of Cape Town, 2014), the surgical case count is likely to increase leaving more scope of research and further learning concerning this patient population. The study by Reiche et al., 2021) does not entirely encompass the whole population of patients undergoing median sternotomy as its focus was only on patients undergoing CABG via median sternotomy technique. 14 | P a g e 2.3.3. Current physiotherapy treatment post median sternotomy As stated by Derakhtanjani et al. (2019), the goal of physiotherapy amongst patients undergoing cardiac surgery via median sternotomy surgical approach is to prevent post- operative complications thereby reducing morbidity and mortality as well as reducing length of hospital stay and hospital costs. This may be done by; reducing post-operative pain, reducing secretion retention, and enhancing secretion clearance; maintaining or enhancing lung volume; correcting ventilation perfusion (V/Q) ratio; reducing airway resistance and improving inspiratory as well as global muscle strength (Perelló-Díez & Paz-Lourido, 2018). 2.3.3.1. pre-operative physiotherapy Pre-operative evaluation and treatment is just as crucial in aiding in the prevention of post- operative pulmonary complications as is post-operative rehabilitation (Valkenet et al., 2013) (level of evidence 4). Inspiratory muscle training (IMT) when used pre-operatively has proven useful in prevention of post-operative atelectasis and pneumonia. This finding was based on the use of IMT for 15-30 minutes, five to seven times per week, for at least two weeks prior to surgery. Recommended loads vary from 10-60% of maximal inspiratory pressure as tolerated.(Katsura et al., 2015) (level of evidence 1a). Cessation of smoking and alcohol consumption one month prior to surgery has also been associated with better surgical outcomes and should be encouraged in the case of elective surgery (Tønnesen et al., 2009) (level of evidence1a). Nakamura et al., (2023) states a need for preoperative orientation to reduce anxiety about the un-known post-operatively. This, amongst patients who underwent cardiovascular surgery, also reduced the incidence of delirium in the ICU (level of evidence 4). Patients should also be educated about the importance of post- operative mobilisation and cough stimulation during preoperative orientation in a further effort to reduce post-operative complications (Castelino et al., 2016; Rodrigues et al., 2021) (both level of evidence 1a) 2.3.3.2. Pain reduction Non-pharmacological interventions for pain relief post median sternotomy are necessary and are 78% effective when used with pharmacological interventions. The application of ice therapy through gel packs applied over the sternotomy incision for 20 minutes prior to administering breathing exercises with an adjunctive device (spirometer) showed significant reduction in pain levels (Zencir & Eser, 2016) (level of evidence 2a). A randomized controlled trial by Racca et al. (2017) amongst 80 patients post median sternotomy showed that osteopathic manipulative therapy (OMT) administered for 15 minutes, once a day for five successive days after discharge from the ICU led to a significant reduction in pain levels measured via the Visual Analogue Scale (VAS) (median value of one) compared to the control group (median value of three). Furthermore, functional respiratory capacity measured 15 | P a g e using an incentivator device was significantly greater in those who received OMT intervention. Osteopathic manipulative therapy consisted of gentle manipulations of the thoracic wall over various areas including the anterolateral aspect of the chest at the diaphragmatic level, directly on the sternal area, and the supraclavicular area. Each area lasted five minutes of manipulation (level of evidence 2a). Kinesiology tape, when fan- shaped tape is applied in a star-like pattern below the clavicles and on the lateral surfaces of the chest, has shown to be effective in pain reduction thereby reducing the amount of opioid consumption (Brockmann & Klein, 2018) (level of evidence 2a). 2.3.3.3. Restoring lung volume Restoration or maintenance of lung volume prevents atelectasis and improves gaseous exchange. Facilitating secretion clearance goes hand-in-hand with restoring gaseous exchange (Lagier et al., 2022) (level of evidence 1b). Current physiotherapy treatment for restoring lung volume amongst this patient population consists mainly of mobilisation, positioning, and deep breathing exercises (with supported huffing and coughing manouvres using a towel or thoracic support device) with or without the use of adjunctive devices such as incentive spirometry (IS), positive expiratory pressure, IMT, intermittent positive pressure breathing (IPPB) and continuous positive airway pressure (CPAP) (Rodrigues et al., 2021) (level of evidence 1a) Despite its regular use, IS has been shown to have no effect in reducing post-operative pulmonary complications (Eltorai et al., 2018; Freitas et al., 2012) (level of evidence 1b). Positive expiratory pressure (PEP) devices have better evidence with regards to increasing tidal volume thereby reducing post-operative atelectasis. A recent study by Jage & Thakur, (2022) found that oscillatory PEP devices such as the Acapella when used in conjunction with other physiotherapy modalities offers better airway clearance and promotes greater lung volume than conventional physiotherapy (consisting of manual chest clearance techniques, IS and deep breathing exercises) alone amongst patients who underwent CABG via median sternotomy surgical approach. This information should be taken with caution as the study was a pilot consisting of a small sample size (20 participants who underwent CABG surgery via median sternotomy surgical approach of which 11 were in the experimental group and nine were in the control group). The outcome measures included in the study were amount of sputum expectorated, FVC, FEV1, and PEF (level of evidence 2a). Inspiratory muscle training, when used all days during hospitalization along with conventional physiotherapy (manual chest physiotherapy, deep breathing exercises, postural drainage and suctioning), has been shown to improve maximum Inspiratory pressure (MIP), PEF and tidal volume measures by the time of discharge from the hospital when compared 16 | P a g e to the use of conventional therapy alone amongst patients who underwent CABG via median sternotomy surgical approach (Barros et al., 2017) (level of evidence 1a). Although CPAP has been shown to improve oxygenation, it has not been proven superior to other therapeutic techniques (Pasquina et al., 2004) (level of evidence 4). Interestingly there is no evidence that the use of mechanical devices is more effective than breathing exercises alone and it is suggested that there should be a combined use (Urell et al., 2011) (level of evidence 4). Post-operatively, breathing exercises are recommended to be done once every waking hour particularly with patients whose mobilisation status is restricted. To restore vital capacity, both force and depth should be emphasized with a slow and deep inspiration, a passive expiration and a two-to-five second hold in-between (Bianchi et al., 2004) (level of evidence 3). Breathing exercises should be performed in optimal V/Q matching positioning such as standing, sitting, or leaning forward to enhance effectiveness. A suggested duration of exercise is three sets of ten deep breaths with a 30-60 second rest in between sets (Urell et al., 2011) (level of evidence 1b).. 2.3.3.4. Mobilisation Mobilisation out of bed needs to occur within the first 48 hours post-operatively. Patients are encouraged to sit in the chair and walk short distances by day two to be able to walk freely by day three post-operatively. Some studies suggest bed exercises as early as one hour after extubation is beneficial (Ramos dos Santos et al., 2017) (level of evidence1a). The use of assistive devices such as a walking frame or rollator is safe and should be implemented to encourage optimal and safe mobilisation (Reeve et al., 2010) (level of evidence 2a) .da Costa Torres et al.( 2016) in their randomized controlled trial of 66 patients undergoing CABG via median sternotomy surgical approach, developed a post-operative mobilisation protocol which contributed to less post-operative pulmonary complications, greater functional capacity as well as reduced length of hospital stay as compared to a respiratory exercise program only (level of evidence 2a). Table 2.2: A mobilisation protocol following CABG via median sternotomy surgical approach (da Costa Torres et al., 2016) Day 1 •Active upper and lower limb extremity exercises (3 sets of 10 repetitions). •20-minute lower limb cycle ergometer. Day 2 •Progress to walking on spot for 3 sets of 1 minute duration. •20-minute cycle ergometer. Day 3 •Progress to walking in ward (7 minutes). 17 | P a g e •Sit in chair for 30 minutes. Day 4 •Progress walking to 10-minute duration. •Sit in chair for one hour. Day 5 •Progress to walking for 15 minutes. •Sit in chair for at least two hours. Day 6 •Progress to walking for 20 minutes. •Step training up and down one step (3 times continuously on a 20 cm heigh step). Day 7 •Continue walking 20 minutes •Step training up and down one step (6 times continuously on a 20cm heigh step). From day one post-operatively, patients are also encouraged to perform active shoulder exercises at a slow tempo and within a pain free range. Active mobilisation exercises include shoulder flexion, abduction, and scapular adduction movements (Cahalin et al., 2011) (level of evidence 1b). 2.3.3.5. Post-hospital discharge program Prior to discharge from hospital, education about sternal precautions is important in preventing complications regarding the sternal wound (Tuyl et al., 2012) (level of evidence 4). The theme of “keep your move in the tube” is appropriate to use by reminding patients to keep their arms close to their bodies as if they were moving in an imaginary tube (Adams et al., 2016) (level of evidence 1b). This strategy minimizes the outward pull on the sternum when performing activities such as getting out of bed, rolling a wheelchair, pushing open a door and lifting items to put on a high shelf (McKenna et al., 2022) (level of evidence 4). However, for activities that require no heavy lifting such as brushing teeth, “out of tube” movements are permitted (Adams et al., 2016). Additionally, patients should be given thoracic mobilisation exercises at discharge to reduce sternal pain and improve patient satisfaction from physiotherapy treatment (Denehy et al., 2018; Sturgess et al., 2014) (level of evidence 2a) Post discharge, patients are allowed to resume usual activities given that they are pain-free and the principle of “keep your move in the tube” is adhered. Therefore, an activity such as mowing the lawn is doable if a family member is there to assist the patient to pull the cord to start the lawn mower engine (Adams et al., 2016) (level of evidence 1b ). Cahalin et al. (2011) reported that, although sternal precautions are necessary, they can easily become restrictions leading to an individual not optimally functioning in the context of their daily lives and work. Restrictions encountered include reduced shoulder range of motion causing an inability to lift, reach, dress or drive oneself. The authors reported that this could be due to 18 | P a g e Decreased chest expansion decreased depth of breathing /apical breathing pattern ineffective cough hypoxemia Alteration in chest radiographs the fact that either there is no universally accepted list of precautions; the suggestions given by therapists may be anecdotal and not supported by concrete evidence; precautions are applied uniformly to all patients without taking into consideration an individual’s holistic being and how they function in their own personal lives; or the precautions are overly restrictive and lead to fear avoidance behavior (Cahalin et al., 2011; Cohen & Griffin, 2002) (level of evidence 1b). Thus Cahalin et al., (2011) developed a sternal precaution algorithm classifying patients into high risk, moderate risk and low risk of complications. One downside is that they have no clear guidelines as to who is classified into the high, moderate, or low risk groups. Home use of a thoracic support device such as a “heart-hugger” and thoracic stabilization exercises should also be encouraged. Thoracic stabilization exercises should be performed for 10 minutes, twice daily for six weeks (El-Ansary et al., 2019)(level of evidence 2a). Early enrolment into an outpatient cardiac rehabilitation program less than two weeks post discharge from hospital is recommended (Reeve et al., 2010) (level of evidence 2a). Additionally, Zimmerman et al. (2004), found that a six-week program of daily telehealth consultations where education and positive re-enforcement to promote self-efficacy amongst patients who underwent CABG via median sternotomy surgical approach reduced the influence of symptoms on functioning thus promoting re-integration into daily life (level of evidence 2a). The section to follow provides information regarding how a possible BPD in the acute stages post cardiac surgery via median sternotomy surgical approach might influence the presentation of symptoms and results of pulmonary function measures. Key: level of evidence based on hierarchy of evidence fromPolit & Beck, (2010) 2.4. BREATHING PATTERN DYSFUNCTION ACUTE STAGES POST MEDIAN STERNOTOMY 2.4.1. Patient presentation and Pulmonary function measures Figure 2.2: Typical presentation of a patient in the acute stages post-operative median sternotomy as described by Wynne & Botti, (2004). 19 | P a g e 2.4.1.1. Decreased chest expansion measures due to decreased depth of breathing. In terms or ventilation measures, Gissing, (2020), in addition to CE measures, assessed MIP and Peak Inspiratory Flow (PIF) amongst 61 patients who underwent cardiac surgery via median sternotomy surgical approach. The author conducted a longitudinal study where assessments were made at admission and again at hospital discharge. The results showed that, when comparing pre- and post-operative values, there is an overall decline in both upper and lower thoracic expansion measures, and a lower MIP and PIF upon discharge. The assessments were only conducted until discharge and as stated by the author herself, a need for longer term assessment regarding ventilation kinematics needs to be done. A diagnostic accuracy study by de Sousa et al. (2016) on 98 patients in a period of 24-48 hours post-operative cardiac surgery (acute period) established that the defining characteristics of BPD amongst this population includes changes in depth of breathing and pursed lip breathing (high sensitivity) as well as asymmetry in chest expansion with prolonged expiration phase greater than a ratio of 1:2 inspiration and expiration time (high specificity). Although this study has a large sample size, it has limitations as analysis of breathing was done by one nurse expert assessing patients individually through physical exam and patient records thus creating a bias. A much older, outdated study by Ragnarsdὁttir et al. (2004), confirmed that an apical breathing pattern, also known previously as thoracic dominant breathing (Boulding et al., 2016), is seen post-operatively as opposed to a preoperative diaphragmatic breathing pattern. Abdominal movement was found to be 60% of preoperative values while lower thoracic movement was found to be 72% of preoperative values. Respiratory motion was assessed before and after surgery using a Respiratory Movement Measuring Instrument which utilizes sensors placed on each side of the chest at the levels of the fourth and ninth ribs as well as lateral to the umbilicus. Limitations of this study include a small sample size of 20 patients and thoracic cage excursion during breathing was not measured posteriorly therefore changes with expansion of posterior basal lung segments were not assessed. This is because the patients were positioned supine during assessment. Supine is not a functional position, and results could change when the patient is upright due to the role inspiratory muscles (particularly the diaphragm) play in posture control (Katz et al., 2018). This study also did not have a longer follow-up beyond seven days post-operatively where the patients are still in the acute stages of healing. 2.4.1.2. Ineffective cough An effective cough requires three phases: inspiration, compression, and expulsion. During inspiration, lung volumes increase to 85-95% of their inspiratory capacity to have a total 20 | P a g e cough volume of 2.3± 0.5 L. During compression, pleural and alveolar pressures rise due to an expiratory force against a closed glottis. During expulsion, the glottis opens, and contraction of abdominal muscles expels secretions and air from the airways. Any alterations to any of these phase’s results in an ineffective cough (Schramm, 2000). Gissing, (2020) in the previously mentioned study, identified a significant difference of median MIP at discharge (30.66 cmH20) compared to admission (55cmH20). According to Kang et al., (2006), although an outdated study, explained that a large amount of air needs to be inspired for an effective cough to take place, and although the expiratory muscles play an important role in cough effort, the lung volume attained prior to the cough is equally as important as it creates an optimal length-tension relationship for the expiratory muscles to contract. Lung volume is determined by the inspiratory muscles during the inspiratory phase of the cough. The authors, in their prospective single center study amongst 40 patients who sustained cervical spinal cord injuries established a more significant correlation between voluntary cough effort and MIP (r=0.599, p<0.001) compared to voluntary cough effort and Maximal expiratory pressure (MEP) (r=0.459, p<0.005). Therefore, in the presence of inspiratory muscle weakness, it has been proven that cough effectiveness is diminished despite normal expiratory muscle contraction. According to Boulding et al., (2016) thoracic dominant breathing (seen amongst patients who underwent cardiac surgery via median sternotomy surgical approach (Ragnarsdóttir et al., 2004)) leads to minimal inspiratory reserve capacity and thus, in this way, BPD can affect cough effectiveness. 2.4.1.3. Hypoxemia Baobao Li et al., (2022) in their retrospective study on the effectiveness of post-extubation prone positioning amongst patients who underwent cardiac surgery via median sternotomy surgical approach to resolve hypoxemia, found that, the postural adjustment was safe and effective to use. Using a P/F ratio of less than 150 mmHg to identify hypoxemia amongst this population group, the authors found that from August 2018 to August 2020, prone positioning had to be utilized a total of 74 times amongst 22 patients post-extubation. Gissing, (2020) in her longitudinal observational study found that, amongst 61 participants who underwent cardiac surgery via median sternotomy surgical approach, oxygen saturation levels were significantly lower when compared to admission values (p=0.001). She hypothesized that this could be due to the hypermetabolic state because of inflammation following surgical trauma which utilizes more blood oxygen. Other causes could be due to loss of blood during surgery, blood transfusions, fluid overload, hypothermia as well as myocardial dysfunction lowering its contractility therefore affecting output (Parolari et al., 21 | P a g e 2003). Altered ventilation mechanics as a result of BPD can also play a role due to reduction in lung volume and capacity leading to limitations in appropriate gaseous exchange further contributing to the hypoxemia (Spoelstra-De Man et al., 2015). 2.4.1.4. Alterations in chest radiographs Multiple studies have shown that chest radiographs taken post-operatively show an increased incidence of atelectasis, pleural effusions and loss of lung volumes seen with elevated hemidiaphragms amongst patients who underwent cardiac surgery via median sternotomy surgical approach (Elkolaly et al., 2018; Gissing, 2020; Kristjánsdóttir et al., 2004). These findings are often not resolved up to a year-post-operatively (Kristjánsdóttir et al., 2004). The previously described BPD amongst patients who underwent cardiac surgery via median sternotomy surgical approach (thoracic dominant breathing) (Boulding et al., 2016), has been proven to lead to loss of lung volume because of loss of tidal volume due to loss of depth of inspiration (Delgado & Bajaj, 2019). In this way, BPD affects chest radiograph findings. 2.4.1.5. Alterations in pulmonary function tests Decreased Forced Vital Capacity (FVC) Decreased Vital Capacity (VC) Decreased one-second forced expiratory volume (FEV1) Decreased FEV1/FVC Decreased Inspiratory Capacity (IC) Decreased Peak Inspiratory Flow (PIF) Decreased functional residual capacity (FRC) Decreased residual volume (RV) 22 | P a g e Figure 2.3: Typical alterations seen in pulmonary function tests in the acute stages post- operative median sternotomy. Previous studies have established significant reductions in pulmonary function tests amongst patients who have underwent cardiac surgery via median sternotomy surgical approach. These tests included: forced vital capacity (FVC); FEV1; FEV1/FVC; forced expiratory flow in 50% and 75% expiration; PEF; maximal voluntary ventilation (Aris et al., 1999; Fayazi et al., 2021; Shenkman et al., 1997); MIP; MEP (Chetta et al., 2006); PIF(Gissing, 2020); inspiratory capacity (Narayanan & Syed Hamid, 2020), and FRC (Calderon et al., 2009). Furthermore, studies by Fayazi et al., (2021); and Shenkman et al. (1997) found that the results of the pulmonary function tests did not return to pre-operative values several months post-operatively. Thoracic dominant BPD seen amongst this population group in the acute stages post- operatively (Boulding et al., 2016) causes alterations in the mentioned pulmonary function tests due to its restrictive effects on the mechanics of breathing (Al-Ashkar et al., 2003; Jage & Thakur, 2022; Westerdahl et al., 2003). 2.4.2. Breathing pattern dysfunction and Post-operative pulmonary complications A median sternotomy surgical technique has been proven to alter breathing pattern from predominantly basal/ diaphragmatic breathing pattern to an upper thoracic breathing pattern thereby predisposing patients to impaired respiratory muscle strength, reduced pulmonary function and atelectasis which can eventually result in pneumonia (Ragnarsdóttir et al., 2004; Roncada et al., 2015). Furthermore, pulmonary measures including VC, IC, FEV1, PEF and total lung capacity (TLC) have been shown to be decreased post-operatively indicating a restrictive pattern of pulmonary function which coincides with the upper thoracic pattern of breathing (Jage & Thakur, 2022; Westerdahl et al., 2003). Post-operative complications such as pneumonia and atelectasis can lead to increased mortality and morbidity amongst patients with an increase in hospitalization costs and overall length of hospital stay (Mans et al., 2015). Having established a link between BPD and pulmonary function deficits in the acute stages post cardiac surgery via median sternotomy surgical approach, the following section might establish a lingering long-term BPD in the said population. 23 | P a g e 2.5. BREATHING PATTERN DYSFUNCTION LONG -TERM POST MEDIAN STERNOTOMY. 2.5.1. Influences of pain A review done by Zubrzycki et al. (2018) stated that post-operative pain caused by trauma to tissues during cardiac surgery may persist for up to three months. Pain impairs basal thoracic expansion, weakens abdominal and intercostal muscles, and alters pattern of breathing leading to reduced inspiratory capacity thereby decreasing lung volume. This contributes to the incidence of post-operative pulmonary complications (Zencir & Eser, 2016). Furthermore, chronic post-operative pain (pain lasting at least three to six months) has an occurrence rate of 30-50% amongst patients who underwent cardiac surgery. Therefore, if there is persistent pain post-operatively, it is likely there will be restricted deep breathing leading to a persistent BPD (Zubrzycki et al., 2018). 2.5.2. In relation to lung function tests and respiratory movements An outdated study by Westerdahl et al., (2003), which has a long follow up of four months post CABG via median sternotomy, involved 25 male patients. Patients were assessed three times; before surgery, four days after and four months after that. Pulmonary function tests were done using a Medical Graphis PF/DX Pulmonary Function system. Levels of pain at rest, taking a deep breath and coughing were also assessed using the VAS. Patients presented with normal lung function pre-operatively but displayed a severe restriction in ventilation four days after surgery. Similarly at four months post-operatively, patients still showed a significant reduction in lung function with a deficit of 6-13% preoperative values in VC, IC, FEV1, PEF, FRC and TLC. Contrary to what was found in the studies by Zencir & Eser, (2016) and Zubrzycki et al., (2018) , pain levels were low and not correlated to the restrictive breathing impairment seen four months post-operatively. Authors suggest the cause for the dysfunction to be related to reduced thoracic cage expansion due to alterations in the tissues following opening of the thorax rather than pain. This study proves the need for updated research and therapeutic intervention with longer term follow up as deficits in pulmonary function seem to be long lasting and can become permanent (Westerdahl et al., 2003). The most recent study on pulmonary dysfunction post cardiac surgery at one year follow-up also noted that long-term evaluation of BPD is lacking. This study showed that pulmonary function measured as VC, forced vital capacity (FVC), FEV1, FEV1/FVC, PEF and FRC was significantly reduced compared to pre-operative values (2-5% impairment). This study has a large sample size of 164 patients who underwent CABG, valve replacement or a combination of two performed via a median sternotomy surgical approach. The authors however did state that there is a need to identify risk factors for the development of long- 24 | P a g e term breathing dysfunction. Despite their measures of pulmonary function, the authors did not assess actual chest wall breathing pattern or mechanics (Westerdahl et al., 2016). Unlike Westerdahl et al. (2016), Kristjánsdóttir et al. (2004) in an older study utilized a time frame where they assessed 20 patients before, three months and one year after cardiac surgery via median sternotomy surgical approach. Their aim was to examine alterations in chest wall motion and pulmonary function amongst this population group. Their outcome measures included bilateral respiratory movements using a Respiratory Movement Measuring Instrument (sensors positioned bilaterally at the level of the umbilicus, the ninth and fourth ribs) as well as pulmonary function tests measuring VC, FVC, FEV1 using Pulminet III. Their results showed significant decrease in basal/ abdominal movement as compared to preoperative values which did not normalize by 12 months. Interestingly, the authors noted an increase in chest expansion of the upper and lower thoracic movements which they hypothesize is due to over-stretch injury of the connective tissues of the costovertebral and costotransverse joints of the thoracic cage during surgery as these structures are not able to contract to their original length and remain elongated. They also found that lung volumes did not decrease greatly at three months post-operatively as compared to preoperative measures (volumes decreased 11-14%). This could be because decreased motion of the abdomen during breathing was compensated for by increased upper and lower thoracic motions thereby helping to maintain lung volume. Limitations in this study included a very small sample size as well as the authors did not relate pulmonary deficits to function and thus concentrated only on altered mechanics of breathing and not how it holistically affects the patients in their daily lives. The section to follow will discuss the prevalence of functional status deficits post cardiac surgery with focus on the diaphragm as a postural control muscle. 2.6. EFFECT OF LONG-TERM BPD ON RETURN TO WORK AND FUNCTIONAL PERFORMANCE 2.6.1. Functional status post cardiac surgery Although there is a need for newer data, patients who underwent CABG surgery via median sternotomy surgical approach, reported functional deficit when doing home chores two months post-operatively. These patients reported that they either found the activities difficult to perform (56%) or needed assistance to perform (36%) and/or experienced pain during the activity (44%) (LaPier et al., 2008). Furthermore, another, yet outdated study revealed that 36% of patients report dissatisfaction with their functional status one year post-operatively (Falcoz et al., 2003). 25 | P a g e Breathing pattern dysfunction, seen in the acute stages post-operatively, has also been proven to have a correlation with poor functional movement levels (Bradley & Esformes, 2014). 2.6.2. The diaphragm “The diaphragm is one of the most remarkable areas in the body in that it has so much influence and the consequences of its dysfunction can manifest anywhere from the head to the toes” (Stone, 1999, p9) The zone of apposition (ZOA) describes the area of attachment between the diaphragm and the rib cage. The diaphragm has three ZOA areas namely: fibers attaching onto the posterior surface of the xiphoid process of the sternum; fibers attaching onto the inner surface of the lower six ribs at their costal margins and fibers attaching to the first three lumbar vertebrae (Moore et al., 2014). Any disruptions to the ZOA eg, damage to the sternal attachments of the diaphragm during a median sternotomy in the case of cardiac surgery, leads to a decreased ability of the diaphragm to contract optimally leading to decreased efficiency in inhalation. Secondary mechanical compensations to this include reduced thoracic expansion, with increased accessory respiratory muscle use and postural alterations. This results in symptoms such as dyspnea, decreased exercise tolerance, increased lumbar lordosis with shortened hamstrings, lumbo-pelvic instability, paraspinal muscle spasm, general low back pain, thoracic outlet syndrome, sacroiliac joint pain and headaches (Kocjan et al., 2017). 2.6.3. Balance and stability Although the diaphragm has a principle role of respiration particularly that of inspiration, it has a crucial role in balance and postural control as it, along with co-contraction of multifidus, transversus abdominis and pelvic floor muscles, aids in increasing intrabdominal pressure thereby bracing the lumbar spine and allowing for stabilization (Bradley & Esformes, 2014; Kocjan et al., 2018). Stabilization of the trunk involving the contraction of the diaphragm which tenses the thoracoabdominal fascia via its cural fibers happens before initiation of functional movement and is independent of the phase of respiration. This suggests that this is a nonvoluntary response pre-programed by the brain and spinal cord (Kocjan et al., 2018). Both static and dynamic balance is needed in basic functional movements and postures seen in activities of daily living such as standing, walking, and turning around (Bradley & Esformes, 2014; Kocjan et al., 2018). Any deficits in diaphragm function can lead to reduced balance and stability of the lumbar spine thereby altering motor control. A study done on 34 healthy men and women to determine the relationship between BPD and dysfunctional 26 | P a g e movement revealed a correlation between low scores on the FMS and upper chest breathing patterns measured with the HiLo Breathing Assessment, Nijmegen Questionnaire, Breath holding Ability and Capnography device (Bradley & Esformes, 2014). As discussed previously by Moreno et al. (2011), phrenic nerve injury has a prevalence of 26% amongst these patients undergoing surgery via median sternotomy surgical approach resulting in diaphragm paresis also resulting in altered breathing patterns. Thus, there is a high likelihood of balance and stability deficit amongst this patient population. A study by Kocjan et al. (2018) done on 102 participants ( group one=62 patients before resection due to lung cancer ; group two= 40 of the previous group assessed three-to-five days after the said surgical procedure ; group three= 40 healthy students enrolled at a University) found better static balance performance ( assessed using a Zebris FDM-S platform) amongst participants with greater values of diaphragm muscle thickness, greater index of diaphragmatic thickening ( difference in the thickness of the diaphragm at end inspiration and end expiration) and greater diaphragm excursion during quiet breathing, deep breathing and sniff maneuver. Furthermore, the authors established that there is a correlation between reduced static balance ability and diaphragm muscle strength and function amongst patients post thoracic surgery. Although this study is beneficial in establishing the relationship between diaphragmatic function and static balance control, it does not involve assessment of dynamic balance control which is involved in higher order activities such as reaching for a high shelf or climbing up/downstairs. There is very sparse evidence of the effect of the diaphragm on dynamic balance. A clinical trial with a much smaller sample size (n=13) of healthy university-going adults found that there was a statistically significant relationship between a low error rating in the single leg stance score (SLS) assessing static balance ability, and improvements in diaphragmatic breathing pattern. However, there were no statistically significant correlation scores between improvements in breathing pattern and dynamic balance measured using the OptoGait’s “March in Place” protocol, after an eight-week deep breathing exercise program. The authors did state that the dynamic balance testing done could have been flawed due to equipment malfunction with addition to no empirical data to support OptoGait protocol use in research studies (Stephens et al., 2017). Therefore, early assessment and treatment of BPD will not only aid in breathing but overall performance in activities of daily living thereby improving quality of life (Vidotto et al., 2019). 27 | P a g e 2.7. CONCLUSION This literature review concludes the need for further research involving BPD amongst individuals who underwent cardiac surgery via median sternotomy surgical approach due to the under reporting of the prevalence of BPD in various population groups. Also, this literature review has identified certain alterations in pulmonary function tests which have been established to not have been resolved up to one year post-operatively amongst patients who underwent the median sternotomy surgical approach. This links to the possibility of a prolonged BPD due to the already established link between certain measures of BPD (such as chest expansion) and pulmonary function test results. Additionally, as this literature review has related the role of the diaphragm with the ability to execute functional tasks at home and in the workplace, further research is also needed to establish how work- related demographics, such as return to work time and type of work may influence or be influenced by a possible long-term BPD. 28 | P a g e CHAPTER 3 3. METHODOLOGY 3.1. INTRODUCTION This section will discuss the methodology used to address the objectives and aims of the study to answer the research question. 3.2. TYPE OF STUDY This study was an observational cross-sectional study as each participant was assessed once (Setia, 2016). 3.3. STUDY PARTICIPANTS 3.3.1. Source of Study Participants Participants were selected based on their admission into a private hospital in Pretoria, South Africa where they underwent an elective cardiac procedure via median sternotomy surgical approach at the cardiothoracic unit of the hospital. Participants were identified by the relevant physiotherapist practices who provided care to the patients during their hospital stay following the surgical procedure. 3.3.2. Sample Selection Potential study participants were recruited according to the following inclusion and exclusion criteria: 3.3.2.1. Inclusion Criteria •Male and female patients who underwent cardiac surgery where a median sternotomy surgical approach within a period of three months to one year prior, were used. •Patients who were able to provide informed consent. •Patients aged 18-65 years. 3.3.2.2. Exclusion Criteria •Patients who underwent a median sternotomy due to a non-cardiac origin (e.g., Lung masses or trauma). •Patients with underlying chronic lung pathologies such as chronic obstructive pulmonary disease. •Patients who had undergone a surgical re-look. •Patients who were participating in another clinical trial at the time 29 | P a g e 3.3.3. Sample size: Based on advice given by a statistician, total population sampling was used. The total population of patients who had undergone cardiac surgery via median sternotomy surgical approach within a period of one year was selected. In the specific private hospital, a total of 120 patients underwent the above-mentioned surgical procedure the previous year (February 2021-February 2022). Of that population, an estimated 20% demised. Taking into consideration an expected “ non-response “rate of up to 30% based on a study by Abrahamsen et al., (2016) as an estimated population size of 60 was expected to be used for the study. 3.4. VARIABLES 3.4.1. Independent Variables: •Health-related profile of the patients who underwent cardiac surgery via median sternotomy surgical approach (BMI, previous diagnosis of depression, length of hospital stay, pain levels as measured using the Visual Analogue Scale, post-operative complications). •The median sternotomy approach used by the cardiothoracic surgeon for this chosen patient population. •Return to work time. 3.4.2. Dependent Variables: •The presence of BPD as determined by the NQ, SEBQ, BHT, and CE Measurements. 3.4.3. Confounding Variables: •Age and gender •Work-related demographics (type of work, level of education, income bracket). •The physical activity level as determined by the Physical Activity Vital Sign (PAVS). 3.5. OUTCOME MEASURES As stated in the introduction, there are no gold standard methods to define BPD, but it has been suggested that a multidimensional approach should be used incorporating biomechanical, biochemical, and psychophysiological dimensions when assessing this phenomenon (Courtney, 2011). Therefore, the following outcome measures have been used to enable assessing for BPD within all three dimensions in the current study. 30 | P a g e 3.5.1. Nijmegen Questionnaire (psychophysiological dimension) The NQ is a breathing symptom questionnaire originally created to evaluate hyperventilation syndrome, but it has since been used across a variety of medical specialities from pulmonology to otorhinolaryngology to assess BPD (van Dixhoorn & Folgering, 2015). This questionnaire consists of four questions relating to respiratory symptoms while the other 12 relate to stress and anxiety (Courtney, 2011; Van Dixhoorn & Folgering, 2015). A cut-off score of 20 or more denotes a BPD with a sensitivity of 91% and a specificity of 92% (Azizmohammad Looha et al., 2020). It has also been proven to have a strong test-retest reliability (IR=0,98) and a strong correlation with the SEBQ (p=0.0001)(Courtney, Greenwood, et al., 2011). 3.5.2. Self-Evaluation of Breathing Questionnaire (psychophysiological dimension) The SEBQ is also a breathing symptom questionnaire. This questionnaire offers a greater depth of evaluation than the NQ and differentiates symptoms into two dimensions: “lack of air” relating to increased activity of chemoreceptors and ”perception of restricted breathing” which relates to breathing kinematics (Courtney, Greenwood, et al., 2011). To obtain an accurate evaluation, the SEBQ should be used with the NQ as it is still in need of further validation (Courtney, Greenwood, et al., 2011; Mitchell et al., 2016). Scores range from a ”0” which denotes “no impairment” while a score of “75” denotes maximal perception of impairment. According to expert opinion, a cut-off score of 25 or more indicates the presence of BPD (Kiesel et al., 2017). It has been established that the SEBQ has a high test-retest reliability (ICC=0.89) and internal consistency (Cronbach’s alpha=0.93) within the general population (Mitchell et al., 2016). 3.5.3. Breath Hold Time (biochemical dimension) Breath Hold Time or BHT test, describes a test where the participant is asked to hold their breath by pinching their nose after a normal exhalation. This test is done in the sitting position and the amount of time the participant can hold their breath is then measured (Kiesel et al., 2017). Among a general population, BHT has a good inter-rater reliability with ICC=0.88 (0.78- 0.93). When used alone without other outcome measures it has a sensitivity of 0.54 (0.49- 0.58) and a specificity of 0.60 (0.18-0.92) when a cut-off score of 20 seconds is used. Sensitivity scores only improved to 0.74 (0.69-0.77) with a cut-off score of 25 seconds (Kiesel et al., 2017). 3.5.4. Chest Expansion Measurement (biomechanical dimension) Measurement of CE is considered the most important measure of breathing patterns at rest and with exercise. Measurement via a non-stretch tape measure is considered affordable, 31 | P a g e easy to use and non-invasive (Reddy et al., 2019). Measurements of CE are made on two sites; upper CE refers to circumferential measurement with placement at axillary level, while lower CE refers to circumferential measurement with placement at the level of the xiphoid process (Padkao & Boonla, 2020a). Three Measurements are taken at maximal inspiration and maximal expiration for both lower and upper CE and the average difference is noted. This is done in standing and hands at the sides (Debouche et al., 2016) . In terms of correlation, upper and lower CE measurement demonstrates a significant correlation with lung function tests including FVC, FEV1, FEV1/FVC and VC (p<0,0001) (Reddy et al., 2019). Very good intra rater reliability is established for both upper CE (ICC=0.90 and 0.93) and lower CE (ICC=0.85 and 0.86). Good to very good inter-rater reliability is established for both upper CE (ICC=0.83) and lower CE (ICC=0.84) (Reddy et al., 2019). The mean ranges in healthy non-smokers are 5.6-6.4cm for upper CE and 7-7.5cm for lower CE (Reddy et al., 2019). It is however important to note that gender, age, BMI, pain levels, underlying pulmonary conditions and general level of functioning affect these values (Derasse et al., 2021; Reddy et al., 2019). 3.5.5. Physical Activity Vital Sign The PAVS, also known as Exercise Vital Sign (EVS) is a questionnaire enquiring of the duration and frequency of moderate to strenuous exercise performed in a week (Ball et al., 2016). The minimum score for adults older than 18 years of age should be 150 minutes over the period of a week. Additionally, adults should do muscle strengthening activities that are moderate to high intensity involving all major muscle groups at least two days a week (Cowan, 2016). According to Golightly et al. (2017), the PAVS shows a 90% agreeability with the lengthy Modifiable Activity Questionnaire (MAQ) which has a strong correlation with accelerometery. When identifying the presence of inactivity amongst participants, the PAVS, has a 67% sensitivity and a 68% specificity. The PAVS also shows a low positive correlation with accelerometery (P=0.38, P<0.0001). Therefore, it has proved sufficient criterion validity to be used based on identifying a need for further intervention where additional tests will take place thereafter (Kuntz et al., 2021). 3.5.6. Demographic Questionnaire The demographic questionnaire is self-compiled based on previous risk factors causing a delay in return to work, described in the literature review by Mortensen et al. (2021). It also takes into consideration risk factors previously associated with pulmonary complications post-operatively as described in the literature review (Bechtel & Huffmyer, 2020; Gao et al., 2016; Kim et al., 2018; Urell et al., 2016; W. Wang et al., 2014). Classification regarding 32 | P a g e level of education and income bracket (within a South African context) was adapted from Maphupha (2018) and Tuchten (2011) respectively. Table 3.1: Instrumentation and Outcome Measures Outcome Outcome measure Appendix number Psychophysiological dimension of BPD Nijmegen Questionnaire (NQ) and Self-Evaluation of Breathing Questionnaire (SEBQ) 1 and 2 Biochemical dimension of BPD Breath Hold Time Test (BHT) Described above under heading 3.5.3 Biomechanical dimension of BPD Measure of chest expansion (CE) with a non-stretch tape measure 3 Physical activity Physical Activity Vital Sign (PAVS) 4 Work-related demographics Self-created questionnaire which includes questions on: •When and whether the participant has returned to work •Type of work •Level of education •Income bracket 5 Health-related demographics Self-created questionnaire which includes questions on: •Age •Gender •Body Mass Index (BMI) calculated by researcher using height (m) and weight (kg) •Previous diagnosis of depression •Type of surgery •Length of hospital stay •Pain levels during deep breathing and coughing measured using a Visual Analogue Scale (VAS) •Post-operative complications 5 33 | P a g e 3.6. ETHICAL CONSIDERATIONS 3.6.1. Before the study Clearance was obtained through the Human Research Ethics Committee of the University of the Witwatersrand (ref no: M220858 available in appendix 6). Approval of title was also given from the Faculty of Health Sciences Post Graduate Office (Appendix 7). Written permission from the physiotherapy practice owners and cardiothoracic surgeons were also obtained (Appendix 8) . Consent from the chief executive officer of the hospital where the participants underwent the surgery was also given (Appendix 9). 3.6.2. During the study Ethical considerations in accordance with Protection of Personal Information Act (POPIA) (R. Adams et al., 2021) were made with particular focus on data sharing and re-use. Under Section 12 (2) and (18) of the Act, contact details of possible participants were allowed to be shared by the relevant practice owners on the condition that it is was not shared for any purpose other than this research project. In addition, participants were approached by their treating therapist/ surgeon first (whether telephonically or in person) to gain consent thereby avoiding risk of coercion by the researcher. Prior to the study, the participants and their family member/friend were required to sign consent and were allowed to withdraw from the study at any time with no reason required (Appendix 10). To ensure confidentiality, all study results were stored on a password protected database with anti-virus and anti-malware software installed. 3.6.3. After the study After analysis of results, each participant was contacted, and their results discussed. If needed, appropriate education and exercises were sent via email and participants were encouraged to contact their individual physiotherapist if their BPD persists. In the write up of the study, details of participants were made as anonymous as possible. With consideration of POPIA, no personal identifiable data was made available for re-use. 3.7. PILOT STUDY 3.7.1. Pilot study aim •To improve competence and self-efficacy with regards to the use of the outcome measures. •To establish the ease at which the participants can complete the outcome measures as well as the ease of telephonic consultation between the researcher and participant. •To adjust, if necessary, the meth