First, oxygen flow was adjusted to 2 L/min. Before the
start of each measurement, each subject was asked to breathe
for >3 min as preparation to stabilize the F|0 . The F,02 of every
breath was measured for 1 min in each setting. Following data
collection for 1 min, flow was adjusted to 5 L/min, and the same
process (preparation and measurement) was repeated. After an
interval of >30 min, the same course with other oxygen supply
devices (nasal or pharyngeal cannula), position of mouth (open
or closed), and breathing patterns (high or low tidal volume) was
repeated.