Respiratory muscle unloading improves leg muscle oxygenation during exercise in patients with COPD

Autor(es)

Borghi-Silva, A. ^[1] ; Oliveira, C. C. ^[1] ; Carrascosa, C. ^[1] ; Maia, J. ^[1] ; Berton, D. C. ^[1] ; Queiroga, Jr., F. ^[1] ; Ferreira, E. M. ^[1] ; Almeida, D. R. ^[2] ; Nery, L. E. ^[1] ; Neder, J. A. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Fed Sao Paulo, Dept Med, Div Resp Dis, Pulm Funct & Clin Exercise Physiol Unit, UNIFESP, BR-04020050 Sao Paulo - Brazil

^[2] Univ Fed Sao Paulo, Dept Med, Div Cardiol, BR-04020050 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: THORAX; v. 63, n. 10, p. 910-915, OCT 2008.
• Citações Web of Science: 83

Resumo

Background: Respiratory muscle unloading during exercise could improve locomotor muscle oxygenation by increasing oxygen delivery (higher cardiac output and/or arterial oxygen content) in patients with chronic obstructive pulmonary disease (COPD). Methods: Sixteen non-hypoxaemic men (forced expiratory volume in 1 s 42.2 (13.9)% predicted) undertook, on different days, two constant work rate (70-80% peak) exercise tests receiving proportional assisted ventilation (PAV) or sham ventilation. Relative changes (Delta%) in deoxyhaemoglobin (HHb), oxyhaemoglobin (O(2)Hb), tissue oxygenation index (TOI) and total haemoglobin (Hb(tot)) in the vastus lateralis muscle were measured by near-infrared spectroscopy. In order to estimate oxygen delivery (DO(2)est, l/min), cardiac output and oxygen saturation (SpO(2)) were continuously monitored by impedance cardiography and pulse oximetry, respectively. Results: Exercise tolerance (Tlim) and oxygen uptake were increased with PAV compared with sham ventilation. In contrast, end-exercise blood lactate/Tlim and leg effort/Tlim ratios were lower with PAV (p<0.05). There were no between-treatment differences in cardiac output and SpO(2) either at submaximal exercise or at Tlim (ie, DO(2)est remained unchanged with PAV; p>0.05). Leg muscle oxygenation, however, was significantly enhanced with PAV as the exercise-related decrease in Delta(O(2)Hb)% was lessened and TOI was improved; moreover, Delta(Hb(tot))%, an index of local blood volume, was increased compared with sham ventilation (p<0.01). Conclusions: Respiratory muscle unloading during high-intensity exercise can improve peripheral muscle oxygenation despite unaltered systemic DO(2) in patients with advanced COPD. These findings might indicate that a fraction of the available cardiac output had been redirected from ventilatory to appendicular muscles as a consequence of respiratory muscle unloading. (AU)

• Processo FAPESP: 05/00722-0 - A oxigenação muscular periférica durante o exercício dinâmico em pacientes com DPOC: efeitos da redução do trabalho ventilatório induzida pela ventilação não-invasiva com pressão positiva
• Beneficiário: José Alberto Neder Serafini
• Modalidade de apoio: Auxílio à Pesquisa - Regular