Background: Breathing exercises are widely used after cardiac surgery. The duration of exercises in the immediate postoperative period is not fully evaluated and only limited data regarding the effects of home-based breathing exercises after discharge from hospital have been published.
Aim: The overall aim of this thesis was to evaluate the effects of deep breathing exercises with positive expiratory pressure (PEP) and describe lung function and respiratory muscle strength in patients undergoing cardiac surgery.
Participants and settings: Adult participants (n=131) were randomised to perform either 30 or 10 deep breaths with PEP per hour during the first postoperative days (Study I): the main outcome was oxygenation, assessed by arterial blood gases, on the second postoperative day. In Study III, 313 adult participants were randomly assigned to perform home-based deep breathing exercises with PEP for two months after surgery or not to perform breathing exercises with PEP after the fourth to fifth postoperative day. The main outcome was lung function, assessed by spirometry, two months after surgery. Studies II and IV were descriptive and correlative and investigated pre and postoperative lung function, assessed by spirometry, and respiratory muscle strength, assessed by maximal inspiratory pressure, and maximal expiratory pressure.
Results: On the second postoperative day, arterial oxygen tension (PaO2) and arterial oxygen saturation (SaO2) was higher in the group randomised to 30 deep breaths with PEP hourly. There was no improved recovery of lung function in participants performing home-based deep breathing exercises two months after cardiac surgery, compared to a control group. Subjective experience of breathing or improvement in patient perceived quality of recovery or health-related quality of life did not differ between the groups at two months. Lung function and respiratory muscle strength were in accordance with predicted values before surgery. A 50% reduction in lung function was shown on the second postoperative day. High body mass index, male gender and sternal pain were associated with decreased lung function on the second postoperative day. Two months postoperatively, there was decreased lung function, but respiratory muscle strength had almost recovered to preoperative values.