Effects of Expiratory Positive Airway Pressure on Dynamic Hyperinflation During Exercise in Patients With COPD

BACKGROUND: Expiratory positive airway pressure (EPAP) is a form of noninvasive positive-pressure ventilatory support that, in spite of not unloading respiratory muscles during inspiration, may reduce the inspiratory threshold load and attenuate expiratory dynamic airway compression, contributing to reduced expiratory air-flow limitation in patients with COPD. We sought to determine the effects of EPAP on operational lung volumes during exercise in COPD patients. METHODS: This was a nonrandomized, experimental comparison of 2 exercise conditions (with and without EPAP); subjects completed a treadmill exercise test and performed, before and immediately after exercise, lung volume measurements. Those who overtly developed dynamic hyperinflation (DH), as defined by at least a 15% reduction from pre-exercise inspiratory capacity (IC), were invited for an additional research visit to repeat the same exercise protocol while receiving EPAP through a spring loaded resistor face mask. The primary outcome was IC variance (pre-post exercise) comparison under the 2 exercise conditions. RESULTS: Forty-six subjects (32 males), a mean 65.0 +/- 8.2 years of age, and with moderate to severe COPD (FEV1 = 38 +/- 16% predicted) were initially enrolled. From this initial sample, 17 (37%) presented overt DH, as previously defined. No significant difference was found between these subjects and the rest of the initial sample. Comparing before and after exercise, there was significantly less reduction in IC observed when EPAP was used (-0.18 +/- 0.35 L vs 0.57 +/- 0.45 L, P = .02), allowing greater IC final values (1.45 +/- 0.50 L vs 1.13 +/- 0.52 L, P = .02). CONCLUSIONS: The application of EPAP reduced DH, as shown by lower operational lung volumes after submaximal exercise in COPD patients who previously manifested exercise DH.