This systematic review aimed to estimate the effect of preoperative respiratory muscle training (RMT) compared to no intervention on the incidence of post-operative pulmonary complications (PPC), post-operative length of stay, respiratory muscle strength and duration of mechanical ventilation in people following elective open cardiac surgery.

Guided by a prospectively registered protocol, database searches were conducted combining terms related to cardiac surgery, RMT and randomised controlled trials in 12 databases, including Cochrane Central Register of Trials, PubMed/Medline, Embase and PEDro from their inception until July 2021, two clinical trials registers and citation tracking. Two independent authors assessed potential eligible trials against predetermined criteria, methodological quality (using the PEDro scale) and extracted data. The participants were adults undergoing elective open heart surgery with or without cardiopulmonary bypass. RMT was defined as training delivered by inspiratory pressure loading (pressure threshold training), hyperpnoea with normocapnia or inspiration with resistance to flow. The comparison group received no intervention or sham RMT. Primary outcome measures were post-operative pulmonary complications (PPC), length of stay and respiratory muscle strength. Post-operative pulmonary complications were defined as pneumonia, hypoxaemia, hypercarbia, bronchospasm, atelectasis and respiratory failure. Meta-analyses were performed using a random-effects model to obtain effect sizes and their respective 95% confidence intervals (CI). Dichotomous outcomes were reported as risk ratios and continuous outcomes were reported using mean difference. Heterogeneity was assessed using the I-squared statistic. The overall quality of the evidence assessment was assessed using the GRADE approach.

Eight randomised controlled trials were included in the systematic review, published between 1998 and 2019. The eight trials contained data for 696 participants, with a mean age range of 59 to 71 years. Ninety percent of participants underwent coronary artery bypass grafts, 7% underwent valve replacements and the remaining 3% combined surgeries. Trials were from Brazil and the Netherlands (n=3), China (n=1) and the remaining from Israel (n=4). PEDro scores of the included trials ranged from four to eight in quality.
The dose of RMT varied across the eight trials. The initial training pressure commenced at 15% of maximal inspiratory pressure (MIP) (n=1), 30% (n=6) and 40% (n=1). The intervention duration ranged from 5 days (n=1), 2 weeks (n=3) and between 2 to 4 weeks (n=4). Training sessions ranged from one per day up to three times a day, and the training ranged from 3 x 10 inspirations to 30mins. Mortality was reported in 2 trials, with 5 deaths in the control group and 3 in the experimental group.

Compared to no intervention, there was moderate-quality evidence from six trials of 645 participants that RMT lowered the risk of PPC (RR 0.51, 95% CI 0.38 to 0.70) and high-quality evidence that RMT lowered the risk of pneumonia (RR0.44, 95% CI 0.25 to 0.78). There was high-quality evidence from four trials of 531 participants that RMT resulted in shorter hospital length of stay (MD -1.7 days, 95% CI -2.4 to -1.1).

The review concluded that RMT resulted in worthwhile improvements in outcomes that matter to patients. The risk of PPC in general and pneumonia were each reduced by about half, length of hospital stay was reduced by almost 2 days. These results were based on high-certainty evidence with low heterogeneity.

Cursino de Moura JF, Oliveira CB, Coelho Figueira Freire AP, Elkins MR, Pacagnelli FL (2024) Preoperative respiratory muscle training reduces the risk of pulmonary complications and the length of hospital stay after cardiac surgery: a systematic review. Journal of Physiotherapy 70:16–24

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PEDro acknowledges this systematic review summary was prepared by Dr Tiffany Dwyer and Sandeep Gupta from the PEDro Education and Training Committee.