Figure 3.

Quadriceps, intercostal, and abdominal muscle oxygenation responses and metabolic responses. a) Quadriceps muscle oxygen saturation; b) intercostal muscle oxygen saturation; c) abdominal muscle oxygen saturation; and d) arterial lactate concentration recorded at rest, at the time of exhaustion in room air (isotime), and t_lim while patient breathed norm­oxic heliox, pure (100%) oxygen or room air. Isotime data are those obtained on normoxic heliox or 100% oxygen at the same time as at the limit of exercise tolerance on room air.