The cardiorespiratory system integrates systemic and pulmonary circulation while ensuring adequate oxygenation of the body at rest and during exercise. In addition to chronic respiratory problems that mainly affect the lungs, airways and pulmonary vascular system, respiratory capacity and respiratory muscle strength can be negatively affected in a wide spectrum including cardiac diseases, surgeries, neuromuscular diseases, obesity, long-term bed rest, aging and inactivity. Weakness of the respiratory muscles causes important secondary consequences by causing the increased respiratory demands not to be met during physical activity. It has been reported that respiratory muscle training applied within the scope of pre-operative and post-operative cardiac rehabilitation program is beneficial in terms of increasing respiratory functions, reducing the risk of post-operative complications and length of stay. Respiratory muscle training is known to have many potential beneficial effects on patients undergoing cardiac surgery. Different methods and devices are used to improve and develop the functions of the inspiratory and expiratory muscles and each training method and device has differences. Therefore, it is thought that examining the clinical effects of using a personalized breathing exercise device on respiratory functions, respiratory muscle strength and functional capacity in individuals who have undergone cardiac surgery will contribute to the literature.