Inspiratory muscle training to reduce risk of pulmonary complications after coronary artery bypass grafting: a systematic review and meta-analysis

BACKGROUND: Pulmonary complications occur in a substantial proportion of patients who undergo coronary artery bypass grafting. Inspiratory muscle training (IMT), a simple, well-tolerated physical therapy, has been proposed to reduce the risk of complications, but its efficacy remains controversial. METHOD: Randomized controlled trials (RCTs) examining the influence of IMT on the risk of pulmonary complications after coronary artery bypass grafting were identified from PubMed, Embase, CENTRAL, CINAL, and Web of Science through March 2023. Data were meta-analyzed for the primary outcomes of pulmonary complications, defined as pneumonia, pleural effusion, and atelectasis; and in terms of the secondary outcomes of maximum inspiratory pressure, maximum expiratory pressure, length of hospitalization, 6 min walk test, and peak expiratory flow and other outcomes. Risk of bias and quality of evidence assessments were carried out using the RoB 2.0 and Grading of Recommendations Assessment, Development and Evaluation (GRADE) applied to primary outcomes of pulmonary complications. RESULTS: Data from eight RCTs involving 755 patients were meta-analyzed. IMT was associated with a significantly lower risk of postoperative pneumonia [relative risk (RR) 0.39, 95% confidence interval (CI) 0.25–0.62, P < 0.0001] and atelectasis (RR 0.43, 95% CI 0.27–0.67, P = 0.0002), but not pleural effusion (RR 1.09, 95% CI 0.62–1.93, P = 0.76). IMT was associated with significantly better maximum inspiratory pressure (preoperative: mean difference (MD) 16.55 cmH(2)O, 95% CI 13.86–19.24, P < 0.00001; postoperative: mean difference (MD) 8.99 cmH(2)O, 95% CI 2.39–15.60, P = 0.008) and maximum expiratory pressure (MD 7.15 cmH(2)O, 95% CI: 1.52–12.79, P = 0.01), and with significantly shorter hospitalization (MD −1.71 days, 95% CI −2.56 to −0.87, P < 0.001). IMT did not significantly affect peak expiratory flow or distance traveled during the 6 min walk test. CONCLUSIONS: The available evidence from medium and high quality trials suggests that IMT can significantly decrease the risk of pneumonia and atelectasis after coronary artery bypass grafting while shortening hospitalization and improving the strength of respiratory muscles. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/prospero/, identifier: CRD42023415817.