Effects of Respiratory Muscle Training on Pulmonary Function in Individuals with Spinal Cord Injury: An Updated Meta-analysis

Objective. To investigate the pulmonary function responses to respiratory muscle training (RMT) in individuals with tetraplegia and provide a systematic review of the included studies. Methods. Computerized retrieval of randomized controlled trials (RCT) in PubMed, Embase, and the Cochrane Library on the improvement of respiratory function in patients with spinal cord injury by RMT was conducted until May 2019. Two researchers independently screened the literature, extracted the data, and evaluated the risk of bias in the included studies. Articles were scored for their methodological quality using the Cochrane Collaboration risk of bias assessment tool. Results. Sixteen studies were identified. A significant benefit of RMT was revealed for five outcomes: force vital capacity (FVC, WMD: -0.43, 95% CI -0.84 to -0.03, P=0.037), vital capacity (VC, WMD: -0.40, 95% CI -0.69 to -0.12, P=0.006), maximal voluntary ventilation (MVV, WMD: -5.89, 95% CI -10.63 to -1.14, P=0.015), maximum static inspiratory pressure (MIP, WMD: -13.14, 95% CI -18.01 to -8.27, P<0.001), and maximum static expiratory pressure (MEP, WMD: -13.08, 95% CI -23.78 to -2.37, P=0.017). No effect was found for forced expiratory volume in 1 s (FEV1). Conclusion. Our findings demonstrate that RMT can effectively improve spinal cord injury pulmonary function of the patient, which is marked by increasing respiratory strength, function, and endurance. Limited by the quantity and quality of the included studies, the above conclusion needs to be verified by more high-quality studies.