Cardiovascular disease is a leading cause of mortality worldwide.1,2 According to the World Health Organization, it is estimated that approximately 23.6 million individuals will succumb to cardiovascular diseases by 2030.3,4 In Iran, cardiovascular diseases contribute to approximately 40 % of all deaths in both genders.4

Among cardiovascular diseases, coronary artery disease accounts for approximately 30 % of all cases.5 The primary approach to treating coronary artery disease involves medication and lifestyle modifications. However, in many cases, coronary artery bypass graft surgery is necessary to prevent complications, enhance survival rates, and alleviate symptoms.6

Despite the well-established benefits of coronary artery bypass graft surgery in improving patient health, this procedure can cause side effects such as insomnia, irritability, depression, limitations in physical activity, anxiety, and respiratory complications.7,8 These complications can significantly affect patients’ quality of life.

Quality of life reflects an individual's perception of various dimensions, encompassing physical, mental-psychological, and social aspects, based on their expectations and standards.9 Enhancing quality of life is the primary objective in the treatment of diverse medical conditions.10 In the context of heart disease, cardiac rehabilitation is a common approach to improve quality of life.11

Cardiac rehabilitation is a comprehensive and multidisciplinary intervention that aims to benefit both patients and their families through exercise, education, and psychological support.12 The rehabilitation process consists of three phases. The first phase, conducted during the patient's hospital stay, focuses on initiating early mobilization and providing education to enhance the understanding of heart disease for both the patient and their family. The second phase, which commences shortly after the patient's discharge, takes place outside the clinical setting. Upon the completion of 36 cardiac rehabilitation sessions, the third phase, known as the maintenance phase, begins.13 Proper implementation of the cardiac rehabilitation program has been shown to reduce mortality rates by 34 % and recurrence of myocardial infarction by 29 %.12

Despite the implementation of cardiac rehabilitation programs, it has been observed that 35 % of patients experience pulmonary complications.14 Furthermore, almost every patient undergoing coronary artery bypass surgery is expected to experience pulmonary complications.15 These respiratory complications can contribute to increased disability, mortality rates, prolonged hospital stay, and higher associated costs.16

To prevent pulmonary complications in patients undergoing heart surgery, various respiratory interventions are employed, including early mobilization, breathing exercises, cough techniques, incentive spirometry, continuous positive airway pressure, and respiratory muscle exercises.17,18 While some sources recommend pulmonary rehabilitation exclusively for patients with pre-existing pulmonary disease or evident symptoms,16,19 a study conducted by Chen et al. demonstrated that patients undergoing coronary artery bypass surgery, even without chronic obstructive pulmonary disease (COPD), experienced improvements in respiratory muscle strength and lung function as a result of pulmonary rehabilitation within two weeks after surgery.20 Additionally, Brage et al. found that pulmonary exercise enhanced pulmonary oxygenation processes.21 Other studies have also indicated the crucial role of respiratory muscles in an individual's overall functioning, with higher respiratory capacity leading to improved quality of life, increased self-efficacy, and reduced hospital stay.22,23

Based on research confirming the positive impact of cardiac rehabilitation on quality of life, as well as studies demonstrating the effectiveness of pulmonary rehabilitation in reducing postsurgical complications, no such study was found in Iran, and foreign studies examined the effect of pulmonary rehabilitation up to 2 weeks after discharge.20 In Iran, the second phase of rehabilitation begins two weeks after coronary artery bypass surgery. Given the high prevalence and severity of coronary artery diseases, the necessity of surgery for a significant portion of patients, the increased likelihood of pulmonary complications in surgical patients, and the importance of their prevention and management, it is crucial to explore the impact of incorporating pulmonary rehabilitation into cardiac rehabilitation on reducing surgical complications. Therefore, this study aimed to investigate the effect of cardiopulmonary rehabilitation in phase II cardiac rehabilitation on the health-related quality of life of patients undergoing coronary artery bypass surgery.