Fig. 1. Graphs of inspired oxygen fraction (Fio2; unfilled circles ) and end-tidal oxygen fraction (FEo2; filled circles ) for each of the three protocols (BTPS). Each graph is a single representative experimental period from one subject, and each point represents a single breath. The start of oxygenation for each protocol is arbitrarily time = 0. For the 3-min protocol (3 min ), the period of oxygenation was 180 s. For the 4DB protocol (4DB ), the four breaths took approximately 20 s in this experimental period. For the 8DB protocol (8DB ), the eight breaths took approximately 55 s in this experimental period. Note that the time scales for the 4DB and 8DB graphs are the same, but different from the time scale for the 3-min graph. O2= oxygen.
