Is Inspiratory Muscle Weakness a Determinant of Endurance Exercise Tolerance During NIV-Supported Exercise in Patients With COPD?

PURPOSE: Previous research has reported that inspiratory muscle weakness is critical to decreased exercise tolerance and exercise tolerance improves with 10 cmH2O pressure support ventilation in patients with chronic obstructive pulmonary disease (COPD). The purpose of this study was to evaluate the effects of proportional assist ventilation (PAV) and continuous positive airway pressure (CPAP) compared with sham on exercise tolerance in patients with and without inspiratory muscle weakness.

METHODS: In a prospective design, 12 of 54 patients were eligible after clinical and comprehensive lung function evaluation, including maximum inspiratory pressure (MIP) measurement. Using baseline measures, participants were divided into 2 age-matched groups that differed in regard to MIP (Group 1, MIP <60 cmH2O, and Group 2, MIP ≥60 cmH2O). Each participant performed 3 constant work rate tests with noninvasive support (PAV, CPAP, sham) in random order on different days at 80% of maximal incremental power.

RESULTS: During the endurance tests, heart rate, peripheral oxygen saturation (SpO2), dyspnea perception scale, and exercise tolerance were measured. There were no significant differences between groups for heart rate, SpO2, dyspnea perception, or exercise tolerance during PAV, CPAP, or sham-supported exercise (P > .05 for all).

CONCLUSIONS: In this small representative group of patients with COPD, inspiratory muscle weakness was not a determining factor of performance during CPAP or PAV-supported aerobic exercise.