Figure 2.

Changes in pulse oximetry during rest and exercise in all experiments. The ordinate displays arterial saturation as measured by pulse oximetry in percent (Sp_O2) and the abscissa displays Naughton work stages. The insert indicates the studies performed with room air (RA), O₂ at flows of 2 L/min (2LO₂), and devices 1 through 4 (D1–D4). The data points are mean values and the brackets indicate 1 SEM. The zero values represent resting observations. A, B, and C depict the experiments performed at regulator settings of 2, 5, and continuous, respectively.