Effect of inspiratory muscle training before cardiac surgery in routine care.

Background: Inspiratory muscle training (IMT) before cardiac surgery has proved to be a promising intervention to reduce postoperative pneumonia in a randomized controlled trial setting. Effects of IMT in routine care have not been reported.

Objective: The purpose of this study was to investigate the effect of IMT before cardiac surgery on postoperative pneumonia in routine care at a Dutch university medical center using propensity scoring.

Design: This was an observational cohort study.

Methods: All candidates for cardiac surgery were preoperatively stratified by a physical therapist for low risk or high risk for postoperative pulmonary complications. Patients at high risk either engaged in an unsupervised IMT program (20 minutes a day) at home for at least 2 weeks before surgery (group 1) or received usual care (no IMT) (group 2). Results in terms of outcome measures were adjusted with propensity scores to reduce bias caused by nonrandom treatment assignment.

Results: The results showed that of the 94 patients at high risk in group 1, 1 patient (1.1%) developed a postoperative pneumonia. In group 2, 8 out of the 252 patients at high risk (3.2%) developed this pulmonary complication (adjusted odds ratio=0.34, 95% confidence interval=0.04-3.38). No significant differences were found regarding median (25th-75th percentile) ventilation time (7 [5-9] hours versus 7 [5-10] hours), length of stay in the intensive care unit (23 [21-24] hours versus 23 [21-25] hours), or total postoperative length of stay (7 [6-11] days versus 7 [5-9] days).

Limitations: The most important limitations of this study were confounding, incomplete data collection, and a low incidence of the primary outcome.

Conclusions: Propensity scoring is believed to be a valuable tool of great potential interest to researchers in the field of observational studies. Whether IMT in routine care resulted in less postoperative pneumonia cannot be concluded.