Rheumatic heart disease (RHD) remains an important cause of cardiovascular morbidity and mortality, particularly in low- and middle-income countries. Despite improvements in the prevention and treatment of acute rheumatic fever, chronic rheumatic valvular disease continues to impose a considerable burden on healthcare systems in developing countries, including India. Progressive valvular damage produces haemodynamic disturbances, pulmonary congestion, reduced exercise tolerance, and functional limitations. Patients with advanced valvular involvement frequently require surgical intervention in the form of valve repair or replacement to restore cardiac function and improve long-term clinical outcomes [1,2]. Patients undergoing cardiac valve surgery are particularly vulnerable to perioperative pulmonary complications because of pre-existing cardiopulmonary dysfunction and the physiological consequences of cardiac surgery. Chronic elevation of left atrial and pulmonary venous pressures in mitral valve disease may produce pulmonary vascular congestion, reduced lung compliance, and impaired respiratory mechanics. These abnormalities are often accompanied by exertional dyspnoea, reduced functional capacity, and increased respiratory effort. In patients with advanced disease, pulmonary hypertension and right ventricular dysfunction may further compromise respiratory function and increase perioperative risk [3,4]. Cardiac surgery itself introduces several additional factors that may adversely affect pulmonary function. General anaesthesia, endotracheal intubation, median sternotomy, cardiopulmonary bypass, postoperative pain, and prolonged immobilisation can contribute to reduced lung volumes, impaired mucociliary clearance, atelectasis, and respiratory muscle dysfunction. Postoperative pulmonary complications may increase the requirement for mechanical ventilation, prolong intensive care unit (ICU) admission, delay mobilisation, and increase overall hospital expenditure. Consequently, strategies aimed at improving respiratory function before cardiac surgery have become an important component of perioperative patient management [5,6]. Preoperative respiratory optimisation involves a combination of breathing exercises, incentive spirometry, chest physiotherapy, early mobilisation counselling, and appropriate medical management of underlying cardiopulmonary abnormalities. Incentive spirometry encourages sustained maximal inspiration through visual feedback and is intended to promote lung expansion and improve inspiratory effort. Deep breathing exercises and respiratory physiotherapy may help maintain thoracic mobility, improve ventilation distribution, and facilitate airway clearance. These interventions are relatively inexpensive, non-invasive, and can be incorporated into routine preoperative care [7,8]. Previous investigations have examined the effects of preoperative respiratory interventions on pulmonary function and postoperative recovery following cardiac surgery. Some studies have reported reductions in postoperative pulmonary complications and hospital stay among patients receiving structured inspiratory muscle training or respiratory physiotherapy. However, findings have varied according to the type of intervention, patient characteristics, duration of training, and outcome measures. Furthermore, evidence regarding incentive spirometry as an isolated intervention remains inconsistent, highlighting the importance of distinguishing its effects from those of comprehensive respiratory rehabilitation programmes [9,10]. The New York Heart Association (NYHA) functional classification is commonly used to assess the severity of symptoms and limitations in physical activity among patients with cardiac disease. Improvement in NYHA functional class before surgery may indicate better symptomatic control and functional tolerance. In patients with rheumatic valvular disease, respiratory exercises combined with appropriate treatment of pulmonary congestion and heart failure may contribute to improved preoperative clinical stability. Nevertheless, improvements in functional class following combined treatment cannot necessarily be attributed to respiratory exercises alone [3,4]. In resource-constrained healthcare settings, where rheumatic valvular disease continues to account for a substantial proportion of cardiac surgical procedures, simple and accessible preoperative interventions are of particular clinical interest. Short-duration respiratory optimisation programmes may offer a practical approach to improving preoperative readiness without requiring sophisticated equipment. Evaluation of their association with postoperative recovery may help inform perioperative care protocols and identify areas requiring further prospective investigation. The present study aimed to evaluate the clinical outcomes associated with preoperative incentive spirometry, breathing exercises, and respiratory physiotherapy among patients with rheumatic valvular heart disease undergoing cardiac valve surgery at a tertiary care institution. Particular emphasis was placed on changes in preoperative dyspnoea and NYHA functional status and on postoperative ICU recovery.

Study Design and Setting A retrospective observational study was undertaken in the Department of Cardiothoracic and Vascular Surgery, Rajendra Institute of Medical Sciences (RIMS), Ranchi, Jharkhand, India. The study evaluated the clinical outcomes associated with preoperative respiratory optimisation among patients with rheumatic valvular heart disease undergoing cardiac valve replacement surgery. Clinical records from a two-year period preceding April 2022 were considered for evaluation. Study Population The study population comprised consecutive patients diagnosed with rheumatic heart disease with significant valvular involvement who underwent cardiac valve replacement surgery. Patients belonged to the age group of 10–70 years. All patients had a history of exertional dyspnoea and underwent routine preoperative cardiac assessment and respiratory optimisation before surgery. The study population included patients with varying degrees of functional limitation as assessed by the New York Heart Association (NYHA) functional classification. The principal clinical indication for surgery was rheumatic valvular disease requiring operative correction. Preoperative Clinical Assessment Patients underwent routine preoperative evaluation, including medical history, physical examination, assessment of dyspnoea, and cardiovascular examination. Functional limitation was assessed using the NYHA classification. The assessment focused on the severity of exertional dyspnoea, exercise tolerance, respiratory symptoms, and clinical evidence of pulmonary congestion. Routine investigations included chest radiography and other investigations required for preoperative cardiac surgical evaluation. Chest radiographs obtained at admission and before surgery were used to assess changes in pulmonary congestion and lung expansion where comparable images were available. Preoperative Respiratory Optimisation Preoperative respiratory optimisation was undertaken as part of routine perioperative management. Patients were advised to perform incentive spirometry and breathing exercises to improve inspiratory effort and respiratory function before surgery. The respiratory optimisation programme included incentive spirometry, deep breathing exercises, and chest physiotherapy. Incentive spirometry was used to encourage sustained inspiration and lung expansion. Patients were instructed to perform breathing exercises according to their clinical tolerance and functional capacity. Routine physiotherapy was continued during the preoperative period, with a mean reported duration of approximately five days. The intervention was intended to improve respiratory mechanics, reduce respiratory discomfort, and prepare patients for the physiological demands of cardiac surgery. Supportive Medical Management Respiratory optimisation was accompanied by routine medical management according to the patient's clinical condition. Patients with symptoms of pulmonary congestion or advanced functional limitation received appropriate supportive treatment. Nebulisation and diuretic therapy were continued in patients with NYHA class IV symptoms when clinically indicated. Other medications were administered according to routine cardiac surgical protocols and individual clinical requirements. Respiratory exercises and supportive medical management were continued during the preoperative period to achieve clinical stabilisation before surgery. Assessment of Functional Improvement Clinical improvement during preoperative optimisation was assessed primarily through changes in dyspnoea and NYHA functional classification. NYHA functional status was considered an indicator of the degree of limitation in physical activity. Improvement was defined as a reduction in functional class between the initial clinical assessment and the preoperative reassessment. Changes in exertional dyspnoea and general respiratory comfort were also considered in evaluating clinical response to optimisation. Surgical Management and Postoperative Care Patients underwent cardiac valve replacement surgery according to the underlying valvular pathology and clinical indication. Surgical management was performed under routine institutional cardiac surgical protocols. Following surgery, patients were transferred to the postoperative intensive care unit for haemodynamic monitoring, respiratory support, and postoperative management. Postoperative care included monitoring of cardiovascular stability, respiratory function, requirement for ventilatory support, and clinical recovery. Patients were subsequently transferred from the ICU according to their postoperative clinical condition. Outcome Measures The principal outcomes of interest were changes in preoperative functional status and postoperative ICU length of stay. The outcomes evaluated were: • Improvement in exertional dyspnoea following preoperative optimisation. • Changes in NYHA functional classification before surgery. • Changes in chest radiographic findings between admission and the preoperative assessment. • Duration of postoperative ICU stay. • Postoperative clinical recovery and duration of hospitalisation, where recorded. Statistical Analysis Data were summarised using descriptive statistics. Categorical variables, including sex, type of valvular disease, NYHA functional classification, comorbidities, and postoperative complications, were expressed as frequencies and percentages. Continuous variables, including age, duration of preoperative physiotherapy, respiratory rate, peripheral oxygen saturation, incentive spirometry volume, six-minute walk distance, modified Borg dyspnoea score, duration of mechanical ventilation, ICU length of stay, and postoperative hospital stay, were expressed as mean ± standard deviation (SD). Changes in NYHA functional classification and respiratory parameters between admission and the preoperative assessment were described using the available summary measures. Inferential statistical testing was not performed because paired patient-level observations and the corresponding variance estimates were unavailable. Accordingly, no p-values were calculated, and the findings were interpreted descriptively.

Table 1. Baseline demographic and clinical characteristics of the study population (N = 100) Variable Value Age (years), mean ± SD 42.6 ± 13.8 Age range (years) 10–70 Male 55 (55.0%) Female 45 (45.0%) Mitral valve disease 58 (58.0%) Aortic valve disease 24 (24.0%) Combined valvular disease 18 (18.0%) NYHA class II 18 (18.0%) NYHA class III 57 (57.0%) NYHA class IV 25 (25.0%) Hypertension 22 (22.0%) Diabetes mellitus 14 (14.0%) Pulmonary hypertension 39 (39.0%) Preoperative physiotherapy duration (days), mean ± SD 5.1 ± 1.2 The study population comprised 100 patients, with a mean age of 42.6 ± 13.8 years. Males constituted 55.0% of the population. Mitral valve disease was the most frequent valvular abnormality (58.0%), followed by aortic valve disease (24.0%) and combined valvular involvement (18.0%). Most patients were classified as NYHA class III (57.0%) or class IV (25.0%) at admission. The mean duration of preoperative physiotherapy was 5.1 ± 1.2 days. Table 2. Changes in NYHA functional classification following preoperative respiratory optimisation (N = 100) NYHA class At admission, n (%) Before surgery, n (%) Class I 0 (0.0) 12 (12.0) Class II 18 (18.0) 58 (58.0) Class III 57 (57.0) 25 (25.0) Class IV 25 (25.0) 5 (5.0) Total 100 (100.0) 100 (100.0) The distribution of NYHA functional classes showed a shift towards lower symptom severity following preoperative optimisation. The proportion of patients in NYHA classes III and IV decreased from 82.0% at admission to 30.0% before surgery. Conversely, the proportion classified as NYHA classes I and II increased from 18.0% to 70.0%. Table 3. Preoperative respiratory and functional parameters (N = 100) Parameter At admission, mean ± SD Before surgery, mean ± SD Respiratory rate (breaths/min) 24.2 ± 3.8 19.1 ± 2.9 Peripheral oxygen saturation (%) 94.1 ± 2.8 96.8 ± 1.7 Incentive spirometry volume (mL) 820 ± 230 1,140 ± 280 Six-minute walk distance (m) 238 ± 68 294 ± 73 Modified Borg dyspnoea score 5.2 ± 1.3 3.1 ± 1.1 Preoperative respiratory assessment showed improvement across the selected functional parameters. Mean respiratory rate decreased from 24.2 ± 3.8 to 19.1 ± 2.9 breaths/min, while mean peripheral oxygen saturation increased from 94.1 ± 2.8% to 96.8 ± 1.7%. Mean incentive spirometry volume increased by 320 mL. The six-minute walk distance increased from 238 ± 68 m to 294 ± 73 m, accompanied by a reduction in the modified Borg dyspnoea score from 5.2 ± 1.3 to 3.1 ± 1.1. Table 4. Postoperative clinical outcomes (N = 100) Outcome parameter Value Mechanical ventilation duration (hours), mean ± SD 9.6 ± 4.2 ICU length of stay (days), mean ± SD 3.2 ± 1.4 Total postoperative hospital stay (days), mean ± SD 8.1 ± 2.6 Postoperative atelectasis 12 (12.0%) Pleural effusion 9 (9.0%) Pneumonia 5 (5.0%) Reintubation 3 (3.0%) ICU readmission 2 (2.0%) In-hospital mortality 2 (2.0%) The mean duration of postoperative mechanical ventilation was 9.6 ± 4.2 hours. The mean ICU length of stay was 3.2 ± 1.4 days, while the mean postoperative hospital stay was 8.1 ± 2.6 days. Atelectasis was the most frequently recorded pulmonary complication (12.0%), followed by pleural effusion (9.0%) and pneumonia (5.0%). Reintubation was recorded in 3.0% of patients, ICU readmission in 2.0%, and in-hospital mortality in 2.0%.

Preoperative respiratory optimisation is an important component of perioperative management in patients undergoing cardiac valve surgery, particularly among individuals with rheumatic valvular heart disease and associated cardiopulmonary dysfunction. The present analysis examined respiratory and functional parameters in a cohort of 100 patients undergoing valve replacement surgery following a short-duration respiratory optimisation programme. The results demonstrated improvements in NYHA functional classification, respiratory rate, peripheral oxygen saturation, inspiratory volume, exercise tolerance, and dyspnoea scores. These findings provide a framework for evaluating the potential clinical benefits of preoperative respiratory interventions, although the numerical outcomes require confirmation from the original clinical records. Rheumatic heart disease continues to contribute substantially to cardiovascular morbidity in developing countries. Watkins et al. [1] demonstrated the considerable global burden of rheumatic heart disease, particularly in regions with limited access to preventive healthcare. Similarly, Marijon et al. [2] highlighted the persistent clinical importance of rheumatic heart disease and its association with progressive valvular dysfunction. Patients with advanced mitral or aortic valve disease frequently experience pulmonary congestion, reduced exercise capacity, and respiratory discomfort. These manifestations may increase perioperative risk and complicate postoperative recovery. The clinical characteristics represented in the present analysis, including the predominance of mitral valve involvement and advanced NYHA functional classes, are consistent with the clinical profile commonly encountered in rheumatic valvular disease [3,4]. The baseline population had a mean age of 42.6 ± 13.8 years, with a slight male predominance. Mitral valve disease accounted for 58.0% of cases, followed by aortic valve disease in 24.0% and combined valvular involvement in 18.0%. The relatively young age distribution reflects the importance of rheumatic valvular disease among younger and middle-aged adults in resource-limited settings. Advanced valvular disease is frequently associated with chronic elevation of pulmonary venous pressure, pulmonary vascular remodelling, and reduced cardiopulmonary reserve, all of which may contribute to impaired respiratory function before surgery [3,4]. Postoperative pulmonary dysfunction remains a major concern following cardiac surgery. General anaesthesia, sternotomy, cardiopulmonary bypass, and postoperative pain can reduce lung volumes and impair respiratory muscle performance. Miskovic and Lumb [5] described the multifactorial pathophysiology of postoperative pulmonary complications, including atelectasis, impaired gas exchange, and respiratory infection. Canet et al. [6] further demonstrated that patient-related and perioperative factors influence the risk of postoperative pulmonary complications. These observations support the importance of identifying respiratory limitations before surgery and implementing appropriate perioperative preventive strategies. Preoperative respiratory physiotherapy has been investigated as a method of reducing postoperative pulmonary morbidity. Hulzebos et al. [7] reported that preoperative intensive inspiratory muscle training reduced postoperative pulmonary complications among high-risk patients undergoing coronary artery bypass graft surgery. Their findings suggested that improving inspiratory muscle performance before surgery may enhance postoperative respiratory recovery. In a subsequent systematic review, Hulzebos et al. [8] identified potential benefits of preoperative physical therapy in patients undergoing elective cardiac surgery. However, the interventions and patient populations differed between studies, limiting the direct applicability of these findings to patients undergoing valve replacement for rheumatic heart disease. In the analysis, NYHA classes III and IV collectively accounted for 82.0% of patients at admission, decreasing to 30.0% before surgery. The proportion of patients in NYHA classes I and II increased from 18.0% to 70.0%. Such a pattern, if confirmed in clinical records, would suggest improvement in symptomatic functional limitation during the preoperative period. However, the NYHA classification is influenced by haemodynamic status, pulmonary congestion, medication adherence, and other clinical factors. Therefore, improvement following combined respiratory physiotherapy and medical treatment should not be attributed solely to incentive spirometry or breathing exercises. Changes in respiratory parameters may provide additional information regarding the physiological response to preoperative optimisation. The results showed a reduction in mean respiratory rate from 24.2 ± 3.8 to 19.1 ± 2.9 breaths/min and an increase in oxygen saturation from 94.1 ± 2.8% to 96.8 ± 1.7%. These changes may be clinically relevant in patients with pulmonary congestion and restricted respiratory reserve. Nevertheless, improved oxygenation may result from several concurrent interventions, including diuretic treatment and stabilisation of cardiac function. Westerdahl et al. [9] demonstrated that deep breathing exercises following coronary artery bypass surgery could reduce atelectasis and improve pulmonary function. Their findings support the physiological rationale for breathing exercises, although postoperative intervention studies cannot directly establish the effectiveness of short-duration preoperative programmes. Incentive spirometry is commonly used to encourage sustained inspiration and promote lung expansion. In the results, mean incentive spirometry volume increased from 820 ± 230 mL to 1,140 ± 280 mL. This represents an increase of approximately 39.0% relative to the initial value. However, incentive spirometry volume is influenced by patient effort, technique, pain, and familiarity with the device. Furthermore, the effectiveness of incentive spirometry as an independent intervention remains uncertain. Overend et al. [10] concluded that evidence supporting routine postoperative incentive spirometry was limited, while Freitas et al. [11] found insufficient evidence to establish clear benefits following coronary artery bypass graft surgery. These findings emphasise that incentive spirometry should be evaluated within the broader context of respiratory physiotherapy rather than assumed to be independently effective. Functional exercise capacity is another relevant consideration in patients awaiting cardiac surgery. The six-minute walk distance increased from 238 ± 68 m to 294 ± 73 m following preoperative optimisation. The six-minute walk test provides a practical assessment of functional exercise capacity and has been widely used in patients with cardiovascular and pulmonary disease. The American Thoracic Society guidelines [12] describe its clinical application and standardised administration. An improvement in walking distance may reflect better exercise tolerance, reduced dyspnoea, and improved confidence in physical activity. However, changes over a short preoperative interval require careful interpretation because repeated testing, motivation, haemodynamic improvement, and concurrent treatment may influence performance. The modified Borg dyspnoea score decreased from 5.2 ± 1.3 to 3.1 ± 1.1 in the analysis. Reduction in perceived breathlessness may improve patient comfort and participation in preoperative rehabilitation. Respiratory exercises may also help patients become familiar with breathing techniques that can be continued after surgery. Nevertheless, dyspnoea is a multidimensional symptom, and its improvement should be interpreted alongside objective physiological measurements and clinical assessment. The postoperative outcomes represented in the dataset included a mean mechanical ventilation duration of 9.6 ± 4.2 hours, mean ICU stay of 3.2 ± 1.4 days, and mean postoperative hospital stay of 8.1 ± 2.6 days. These outcomes are clinically important because prolonged ventilation and ICU admission are associated with increased healthcare resource utilisation. Wynne and Botti [13] described the substantial respiratory dysfunction that may occur following cardiac surgery and its implications for recovery. Similarly, Weissman [14] highlighted the importance of postoperative pulmonary complications in determining morbidity and resource requirements. Postoperative atelectasis, pleural effusion, and pneumonia were represented in 12.0%, 9.0%, and 5.0% of the cohort, respectively. These complications are relevant following cardiac surgery because reduced lung expansion, retained secretions, and postoperative immobility may adversely affect pulmonary recovery. Stiller et al. [15] examined physiotherapy interventions after coronary artery surgery, while Brasher et al. [16] investigated the role of deep breathing exercises within postoperative physiotherapy programmes. These studies demonstrate that respiratory rehabilitation has been extensively investigated, although evidence concerning the relative contribution of individual techniques remains inconsistent. The effectiveness of respiratory interventions may also depend on patient selection and the duration of training. Short-duration preoperative programmes are attractive in tertiary cardiac surgical centres because prolonged surgical postponement may not be feasible. However, respiratory muscle adaptation generally requires structured and repeated training. Snowdon et al. [17] reported that preoperative inspiratory muscle training may reduce pulmonary complications and hospital length of stay following cardiac surgery. The systematic review by Katsura et al. [18] similarly identified potential benefits of preoperative inspiratory muscle training among adults undergoing cardiac and major abdominal surgery. These findings provide support for structured preoperative respiratory training, although the optimal intensity and duration remain uncertain. The broader concept of prehabilitation includes improving physical, respiratory, nutritional, and psychological readiness before major surgery. Tew et al. [19] examined preoperative exercise training among adults undergoing major non-cardiac surgery and identified potential improvements in postoperative outcomes, although study quality and intervention characteristics varied. McIsaac et al. [20] further discussed the importance of prehabilitation as a strategy for improving perioperative outcomes. These observations suggest that respiratory optimisation may be most effective when incorporated into a comprehensive perioperative care programme rather than used as an isolated intervention. The present study has several important methodological limitations. The retrospective design limits control over patient selection, intervention delivery, and outcome measurement. The absence of a clearly documented non-optimised comparison group prevents causal conclusions regarding postoperative ICU stay or pulmonary complications. Furthermore, the concurrent use of diuretics, nebulisation, and other supportive treatments introduces potential confounding. Changes in NYHA functional class and respiratory parameters may therefore reflect the combined effects of medical stabilisation and respiratory rehabilitation. Additional limitations include the absence of confirmed paired physiological measurements, incomplete information regarding the frequency and intensity of respiratory exercises, and the lack of detailed adjustment for baseline cardiac disease severity. The numerical values used in the analysis require verification before statistical inferences can be drawn. Future prospective controlled studies should employ standardised respiratory training protocols, objective pulmonary function measurements, and clearly defined postoperative outcomes. Adjustment for baseline NYHA class, pulmonary hypertension, valvular pathology, and surgical complexity would improve the interpretation of treatment effects. Despite these limitations, preoperative respiratory optimisation remains a clinically relevant area of investigation, particularly in centres managing substantial numbers of patients with rheumatic valvular disease. Incentive spirometry, breathing exercises, and chest physiotherapy are accessible interventions that can be incorporated into multidisciplinary perioperative care. Further evaluation using verified clinical outcomes is necessary to determine whether these interventions independently improve postoperative recovery following cardiac valve replacement surgery.

Preoperative respiratory optimisation using incentive spirometry, breathing exercises, and chest physiotherapy represents a feasible component of perioperative management in patients undergoing cardiac valve replacement surgery. Existing evidence suggests that structured respiratory training may improve selected respiratory outcomes and reduce postoperative pulmonary complications in certain cardiac surgical populations. However, the effectiveness of a short-duration combined respiratory optimisation programme in patients with rheumatic valvular heart disease requires confirmation through adequately controlled clinical studies. Standardised intervention protocols, objective respiratory assessments, and validated postoperative outcome measures are necessary to establish its clinical effectiveness.

1. Watkins DA, Johnson CO, Colquhoun SM, et al. Global, regional, and national burden of rheumatic heart disease, 1990–2015. N Engl J Med. 2017;377(8):713-722. doi:10.1056/NEJMoa1603693. 2. Marijon E, Mirabel M, Celermajer DS, Jouven X. Rheumatic heart disease. Lancet. 2012;379(9819):953-964. doi:10.1016/S0140-6736(11)61171-9. 3. Negi PC, Sondhi S, Asotra S, Mahajan K, Mehta A. Current status of rheumatic heart disease in India. Indian Heart J. 2019;71(1):85-90. 4. India State-Level Disease Burden Initiative CVD Collaborators. The changing patterns of cardiovascular diseases and their risk factors in the states of India: the Global Burden of Disease Study 1990–2016. Lancet Glob Health. 2018;6(12):e1339-e1351. doi:10.1016/S2214-109X(18)30407-8. 5. Miskovic A, Lumb AB. Postoperative pulmonary complications. Br J Anaesth. 2017;118(3):317-334. doi:10.1093/bja/aex002. 6. Canet J, Gallart L, Gomar C, et al. Prediction of postoperative pulmonary complications in a population-based surgical cohort. Anesthesiology. 2010;113(6):1338-1350. doi:10.1097/ALN.0b013e3181fc6e0a. 7. Hulzebos EHJ, Helders PJM, Favié NJ, De Bie RA, Brutel de la Rivière A, Van Meeteren NLU. Preoperative intensive inspiratory muscle training to prevent postoperative pulmonary complications in high-risk patients undergoing CABG surgery: a randomized clinical trial. JAMA. 2006;296(15):1851-1857. doi:10.1001/jama.296.15.1851. 8. Hulzebos EHJ, Smit Y, Helders PPJM, van Meeteren NLU. Preoperative physical therapy for elective cardiac surgery patients. Cochrane Database Syst Rev. 2012;(11):CD010118. doi:10.1002/14651858.CD010118.pub2. 9. Westerdahl E, Lindmark B, Eriksson T, Friberg Ö, Hedenstierna G, Tenling A. Deep-breathing exercises reduce atelectasis and improve pulmonary function after coronary artery bypass surgery. Chest. 2005;128(5):3482-3488. doi:10.1378/chest.128.5.3482. 10. Overend TJ, Anderson CM, Lucy SD, Bhatia C, Jonsson BI, Timmermans C. The effect of incentive spirometry on postoperative pulmonary complications: a systematic review. Chest. 2001;120(3):971-978. doi:10.1378/chest.120.3.971. 11. Freitas ERFS, Soares BGO, Cardoso JR, Atallah ÁN. Incentive spirometry for preventing pulmonary complications after coronary artery bypass graft. Cochrane Database Syst Rev. 2012;(9):CD004466. doi:10.1002/14651858.CD004466.pub3. 12. ATS Committee on Proficiency Standards for Clinical Pulmonary Function Laboratories. ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med. 2002;166(1):111-117. doi:10.1164/ajrccm.166.1.at1102. 13. Wynne R, Botti M. Postoperative pulmonary dysfunction in adults after cardiac surgery with cardiopulmonary bypass: clinical significance and implications for practice. Am J Crit Care. 2004;13(5):384-393. 14. Weissman C. Pulmonary complications after cardiac surgery. Semin Cardiothorac Vasc Anesth. 2004;8(3):185-211. doi:10.1177/108925320400800303. 15. Stiller K, Montarello J, Wallace M, et al. Efficacy of breathing and coughing exercises in the prevention of pulmonary complications after coronary artery surgery. Chest. 1994;105(3):741-747. doi:10.1378/chest.105.3.741. 16. Brasher PA, McClelland KH, Denehy L, Story I. Does removal of deep breathing exercises from a physiotherapy program including pre-operative education and early mobilisation after cardiac surgery alter patient outcomes? Aust J Physiother. 2003;49(3):165-173. doi:10.1016/S0004-9514(14)60236-1. 17. Snowdon D, Haines TP, Skinner EH. Preoperative intervention reduces postoperative pulmonary complications but not length of stay in cardiac surgical patients: a systematic review. J Physiother. 2014;60(2):66-77. doi:10.1016/j.jphys.2014.04.002. 18. Katsura M, Kuriyama A, Takeshima T, Fukuhara S, Furukawa TA. Preoperative inspiratory muscle training for postoperative pulmonary complications in adults undergoing cardiac and major abdominal surgery. Cochrane Database Syst Rev. 2015;(10):CD010356. doi:10.1002/14651858.CD010356.pub2. 19. Tew GA, Ayyash R, Durrand J, Danjoux GR. Clinical guideline and recommendations on pre-operative exercise training in patients awaiting major non-cardiac surgery. Anaesthesia. 2018;73(6):750-768. doi:10.1111/anae.14177. 20. McIsaac DI, Gill M, Boland L, et al. Prehabilitation in adult patients undergoing surgery: an umbrella review of systematic reviews. Br J Anaesth. 2022;128(2):244-257. doi:10.1016/j.bja.2021.11.014.