Am. J. Respir. Crit. Care Med., Vol 150, No. 3, 09 1994, 742-746.
Breathing route and ventilatory responses to inspiratory resistive loading in humans
T Nishino and T Kochi
Department of Anesthesia, National Cancer Center Hospital East, Chiba, Japan.
In response to ventilatory loading, a number of compensatory mechanisms can
serve to maintain ventilation at or near control levels. To test the
hypothesis that respiratory compensation for inspiratory flow- resistive
load during nasal breathing may be different from that during oral
breathing, we investigated the ventilatory responses to four different
magnitudes of inspiratory flow-resistive loads ("control," "light,"
"moderate," and "severe" loads: 3.5, 15.0, 51.8, 83.3 cm H2O/L/s at a flow
rate of 30 L/min, respectively) during nasal breathing and during oral
breathing in 11 conscious subjects. With the control, light, and moderate
loads, there were no significant differences in tidal volume (VT),
respiratory frequency (f), minute ventilation (VI), and end-tidal (partial)
carbon dioxide pressure (PETCO2) between nasal and oral breathing. With the
severe load, however, VI and f were significantly lower and PETCO2 was
significantly higher during nasal breathing than during oral breathing.
Occlusion pressure (P0.1) progressively increased during both nasal and
oral breathing with increasing magnitudes of loading. However, the value of
P0.1 during oral breathing at the severe loading was significantly higher
than that during nasal breathing. Our results indicate that ventilatory
compensation for the inspiratory flow-resistive load is better during oral
breathing than during nasal breathing.
