Postoperative inspiratory muscle training in addition to breathing exercises and early mobilization improves oxygenation in high-risk patients after lung cancer surgery: a randomized controlled trial

OBJECTIVES: The aim was to investigate whether 2 weeks of inspiratory muscle training (IMT) could preserve respiratory muscle strength in high-risk patients referred for pulmonary resection on the suspicion of or confirmed lung cancer. Secondarily, we investigated the effect of the intervention on the incidence of postoperative pulmonary complications. METHODS: The study was a single-centre, parallel-group, randomized trial with assessor blinding and intention-to-treat analysis. The intervention group (IG, n = 34) underwent 2 weeks of postoperative IMT twice daily with 2 x 30 breaths on a target intensity of 30% of maximal inspiratory pressure, in addition to standard postoperative physiotherapy. Standard physiotherapy in the control group (CG, n = 34) consisted of breathing exercises, coughing techniques and early mobilization. We measured respiratory muscle strength (maximal inspiratory/expiratory pressure, MIP/MEP), functional performance (6-min walk test), spirometry and peripheral oxygen saturation (SpO(2)), assessed the day before surgery and again 3-5 days and 2 weeks postoperatively. Postoperative pulmonary complications were evaluated 2 weeks after surgery. RESULTS: The mean age was 70 +/- 8 years and 57.5% were males. Thoracotomy was performed in 48.5% (n = 33) of cases. No effect of the intervention was found regarding MIP, MEP, lung volumes or functional performance at any time point. The overall incidence of pneumonia was 13% (n = 9), with no significant difference between groups [IG 6% (n = 2), CG 21% (n = 7), P = 0.14]. An improved SpO(2) was found in the IG on the third and fourth postoperative days (Day 3: IG 93.8 +/- 3.4 vs CG 91.9 +/- 4.1%, P = 0.058; Day 4: IG 93.5 +/- 3.5 vs CG 91 +/- 3.9%, P = 0.02). We found no association between surgical procedure (thoracotomy versus thoracoscopy) and respiratory muscle strength, which was recovered in both groups 2 weeks after surgery. CONCLUSIONS: Two weeks of additional postoperative IMT, compared with standard physiotherapy alone, did not preserve respiratory muscle strength but improved oxygenation in high-risk patients after lung cancer surgery. Respiratory muscle strength recovered in both groups 2 weeks after surgery.