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

• Autor(a) principal: Borghi-Silva, Audrey [UNIFESP]
• Data de Publicação: 2008
• Outros Autores: Oliveira, Cristino Carneiro [UNIFESP], Carrascosa, Claudia Regina [UNIFESP], Maia, Joyce [UNIFESP], Berton, Danilo Cortozi [UNIFESP], Queiroga, Fernando [UNIFESP], Ferreira, Eloara Vieira Machado [UNIFESP], Almeida, Dirceu Rodrigues de [UNIFESP], Nery, Luiz Eduardo [UNIFESP], Neder, Jose Alberto [UNIFESP]
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UNIFESP
• Texto Completo: https://repositorio.unifesp.br/handle/11600/30922; https://dx.doi.org/10.1136/thx.2007.090167

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.