Heliox improves oxygen delivery and utilization during dynamic exercise in patients with chronic obstructive pulmonary disease - Chiappa, G R; Queiroga, F; Meda, E; Ferreira, L F; Diefenthaeler, F; Nunes, M; Vaz, M A; Machado, MC L; Nery, L E; Neder, J A (Am J Respir Crit Care Med, 2009)