Dynamics of chest wall volume regulation during constant work rate exercise in patients with chronic obstructive pulmonary disease

Abstract

This study evaluated the dynamic behavior of total and compartmental chest wall volumes [(VCW) = rib cage (VRC) + abdomen (VAB)] as measured breath-by-breath by optoelectronic plethysmography during constant-load exercise in patients with stable chronic obstructive pulmonary disease. Thirty males (GOLD stages II-III) underwent a cardiopulmonary exercise test to the limit of tolerance (Tlim) at 75% of peak work rate on an electronically braked cycle ergometer. Exercise-induced dynamic hyperinflation was considered to be present when end-expiratory (EE) VCW increased in relation to resting values. There was a noticeable heterogeneity in the patterns of VCW regulation as EEVCW increased non-linearly in 17/30 “hyperinflators” and decreased in 13/30 “non-hyperinflators” (P < 0.05). EEVAB decreased slightly in 8 of the “hyperinflators”, thereby reducing and slowing the rate of increase in end-inspiratory (EI) VCW (P < 0.05). In contrast, decreases in EEVCW in the “non-hyperinflators” were due to the combination of stable EEVRC with marked reductions in EEVAB. These patients showed lower EIVCW and end-exercise dyspnea scores but longer Tlim than their counterparts (P < 0.05). Dyspnea increased and Tlim decreased non-linearly with a faster rate of increase in EIVCW regardless of the presence or absence of dynamic hyperinflation (P < 0.001). However, no significant between-group differences were observed in metabolic, pulmonary gas exchange and cardiovascular responses to exercise. Chest wall volumes are continuously regulated during exercise in order to postpone (or even avoid) their migration to higher operating volumes in patients with COPD, a dynamic process that is strongly dependent on the behavior of the abdominal compartment.

Limitation in tidal volume expansion partially determines the intensity of physical activity in COPD

“…OEP assesses changes in end-expiratory chest wall volume (including lung volumes, gas compression, and decompression in the lungs and blood shifts between the lung and extremities), which differs from the well-implemented method to assess end-expiratory dynamic lung hyperinflation by repeated IC maneuvers at regular intervals during exercise. Similarly to previous studies (2,27,29,31) showing that, during cycling, end-expiratory chest wall volume is regulated differently in patients with COPD with varying degrees of lung dysfunction, we have demonstrated that, in less active patients, end-expiratory volume increased progressively (from ϳ0.2 to ϳ0.5 l), whereas, in active patients, end-expiratory volume decreased at low levels of ventilatory requirement and then progressively increased (from ϳϪ0.1 to ϳ0.4 l) (Fig. 3D).…”