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

• Published in: Brazilian journal of medical and biological research 2012-10, Vol.45 (review), p.1276-1283
• Main Authors: Takara, L.S., Cunha, T.M., Barbosa, P., Rodrigues, M.K., Oliveira, M.F., Nery, L.E., Neder, J.A.
• Format: Article
• Language: English
• Subjects: Short Communication
• ISSN: 1414-431X; 0100-879X; 1414-431X
• DOI: 10.1590/S0100-879X2012007500162

This study evaluated the dynamic behavior of total and compartmental chest wall volumes [(V sub(CW)) = rib cage (V sub(RC)) + abdomen (V sub(AB))] 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) V sub(CW) increased in relation to resting values. There was a noticeable heterogeneity in the patterns of V sub(CW) regulation as EEV sub(CW) increased non-linearly in 17/30 "hyperinflators" and decreased in 13/30 "non-hyperinflators" (P < 0.05). EEV sub(AB) decreased slightly in 8 of the "hyperinflators", thereby reducing and slowing the rate of increase in end-inspiratory (EI) V sub(CW) (P < 0.05). In contrast, decreases in EEV sub(CW) in the "non-hyperinflators" were due to the combination of stable EEV sub(RC) with marked reductions in EEV sub(AB). These patients showed lower EIV sub(CW) 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 EIV sub(CW) 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.