Effectiveness of Respiratory Muscle Training in Adults With Pulmonary Hypertension. A Systematic Review and Meta-Analysis

Patients with pulmonary hypertension (PH) may have impaired exercise capacity and quality of life; this may possibly be due to the early onset of dyspnoea associated with respiratory muscle weakness. Respiratory muscle training could improve the condition of these patients, so this study aimed to determine, through a systematic review and meta-analysis, the effectiveness of respiratory muscle training in adult patients with PH.Medline, Embase, CENTRAL, clinical trial registries databases, and grey literature and reference lists of reviews related to the objective were searched up to March 2022. Controlled clinical trials comparing the effectiveness of respiratory muscle training with sham or no intervention in adults with PH were included. Records were independently screened by two authors. The primary outcomes were maximal and functional exercise capacity, quality of life, and dyspnoea. The secondary outcomes were respiratory muscle strength, physical activity, lung function, and adverse events. Two authors independently extracted data and the study quality was assessed using the Cochrane risk-of-bias tool 2 (RoB 2). The certainty of the evidence was assessed according to the GRADE approach.A total of 5,524 records were screened, and seven randomised clinical trials (RCTs) (257 participants) were included. It was uncertain whether inspiratory muscle training (IMT), compared with sham IMT or no intervention, increased the distance walked in the 6-minute walk test (6MWT) (MD, 39 m; 95% CI, 20.72-57.39; I2=27%; four RCTs; very low certainty of evidence) and slightly decreased the perceived sensation of dyspnoea (MD, 0.5 points on the mMRC scale; 95% CI, -0.87 to -0.13; I2=0%; two RCTs; very low certainty of evidence). In addition, it was uncertain whether IMT had no effect on the emotional (SMD, -0.34; 95% CI, -1.06 to 0.38; I2=64%; three RCTs; very low certainty of evidence) and physical (SMD, 0.06; 95% CI, -0.41 to 0.52; I2=16%; three RCTs; very low certainty of evidence) component of quality of life.It is uncertain whether IMT increases functional exercise capacity and slightly decreases the sensation of dyspnoea. In addition, it is uncertain whether IMT does not affect the quality of life. More RCTs and with a better methodological design are needed to increase the certainty of the evidence and determine the real effect of this intervention.