Fig. 1.

Pulse oximetry measurements from PD8 pups exposed to 8% O₂ for 4 h. Arterial O₂ saturation (SPo₂; %) and heart rate (bpm) were measured by fastening sensor clips to each side of the head. One sentinel pup from each experiment was instrumented. Data were gathered continuously (at each heartbeat) for the duration of the experiment. Thirty SPo₂ or heart rate measurements were selected at each time point, chosen at the point in the experiment immediately prior to the chamber being opened. The mean value of these 30 measurements was used as one datum, so each experiment yielded five data points (baseline, 1, 2, 3, and 4 h); n = 4 at each time point. *Significant difference from baseline with P < 0.05.