Acute Effects of Positive Expiratory Pressure on Breathing Pattern and Chest Wall Volumes During Cycle Exercise in COPD Patients

Abstract

Background:

Patients with COPD experience air flow limitation, reduced expiratory capacity, and dynamic hyperinflation (DH), which causes dyspnea and decreased exercise tolerance. Expiratory positive airway pressure (EPAP) is a potential intervention that can reduce DH and improve respiratory muscle efficiency, but its impact on exercise tolerance remains unclear. The aim was to evaluate the acute effects of EPAP during exercise on the respiratory pattern, chest wall volumes, thoracoabdominal asynchrony (TAA), and DH in individuals with COPD using optoelectronic plethysmography.

Methods:

This is a cross-sectional, multi-center study in which the participants were divided in two moments EPAP versus SHAM doing exercise protocols on a cycle ergometer. The protocol consisted of two conditions (a) EPAP—2 min of calm breathing followed by cycling at 80% of maximum load with a 7.5 cm H₂O EPAP mask until exhaustion; and (b) SHAM—the same procedure without EPAP. Effects of EPAP on chest wall volumes, breathing pattern, index of respiratory muscles shortening velocity, the TAA, and paradoxical movements were analyzed. Distribution of the data were tested using Shapiro–Wilk. The Wilcoxon test was used for between-group assessments, and two-way ANOVA or Friedman test was used to compare both groups and phases the protocol. A significance level of P < .05 was used.

Results:

In COPD subjects exercising at 80% of maximum load, both EPAP and SHAM increased chest wall volumes, with EPAP showing greater recovery values and higher abdominal volume (0.74 ± 0.4 L vs 0.58 ± 0.2 L). EPAP maintained higher T_I, T_E, and T_tot at 50%T_lim (Time to Limitation) and T_lim but had lower minute ventilation (T_lim 29.6 ± 11.7 vs 34.7 ± 13.1 L/min, P < .001) and reduced exercise tolerance (P = .001) with greater dyspnea (P = .001). It also increased end-inspiratory chest wall volume at 50% T_lim and recovery (P < .001), sustained rib cage expansion, and reduced diaphragm shortening velocity during exercise. Phase angle differences indicated more TAA with EPAP at T_lim (P = .002), although paradoxical movements increased similarly in both groups during exercise.

Conclusions:

The use of EPAP during exercise in subjects with COPD tended to increase dyspnea, increase TAA, and reduce exercise tolerance without significant improvement in DH.