Can maximal inspiratory and expiratory pressures during exercise predict complications in patients submitted to major lung resections? A prospective cohort study.

Objectives: The measurement of maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax) generated at the mouth is an accepted non-invasive clinical method for evaluating the strength of respiratory muscles. The aim of our study was to verify whether PImax and PEmax measured before and after a symptom-limited stair-climbing test are associated with complications in patients submitted to major lung resections.
Methods: In a prospective cohort study of 283 consecutive patients submitted to lobectomy (231) or pneumonectomy (52) with a preoperative symptom-limited stair-climbing test, PImax and PEmax were measured before and immediately after the exercise. PImax and PEmax values were expressed as percentages of predicted values. ΔPImax and ΔPEmax were defined as the percentage difference between the pre- and postexercise values. Logistic regression analysis and the bootstrap resampling technique were performed to identify predictors of cardiopulmonary complications.
Results: On average, PImax dropped by 3.6% and PEmax increased by 0.8% after the exercise. In total, 173 patients (61%) experienced a reduction in their PImax after exercise, while 150 (53%) had their PEmax reduced. Postoperative cardiopulmonary complications occurred in 74 patients (26%). Complicated patients had a greater reduction in their PImax compared with non-complicated patients (8.7% vs 2.1%, P = 0.03), whereas ΔPEmax was similar in complicated and non-complicated patients (0.7% vs 1.3%, P = 0.5). Receiver operating characteristic analysis indicated that the best cut-off for predicting complications was a ΔPImax of 10%. Stepwise logistic regression analysis and bootstrap confirmed that ΔPImax of >10 was associated with cardiopulmonary complications after adjusting for baseline and surgical factors (ΔPImax regression coefficient -0.02, P = 0.09, bootstrap frequency 51%). A progressive increase in complications was observed in patients with greater reduction in ΔPImax after exercise, particularly for values >10% reduction.
Conclusion: The measurement of PImax at the mouth during exercise represents an additional parameter that can be used to refine risk stratification of lung resection candidates and to identify patients who may benefit from inspiratory muscle training.