Fig. 2. Graphs of oxygen uptake at the mouth during oxygenation (BreathO2; filled dots ) and basal oxygen uptake breathing air (BasalO2; dotted line ) for each of the three protocols (STPD). For BreathO2, each point represents one breath. Each graph is a single representative experimental period from one subject. The start of oxygenation for each protocol is arbitrarily time = 0.