The effect of the level of ventilatory assist on the level of respiratory drive in decerebrate cats

Abstract The present study was undertaken to investigate whether, independent of changes in Pa CO 2 , ventilatory assist influences not only the pattern but also the level of the respiratory drive. The experiments were performed on decerebrate and paralyzed cats ventilated by a phrenic-driven servo respirator at three different F i CO 2 levels (0, 0.03, 0.05). The level of ventilatory assist was altered within the range where Pa CO 2 did not exceed 80 Torr. A higher F i CO 2 accompanied a higher level of ventilatory assist. The relationship between the minute phrenic activity and log 10  Pa CO 2 at a given F i CO 2 was linear. No significant difference was found in the regression lines at different levels of F i CO 2 . We conclude that ventilatory assist has little effect on the respiratory drive at a constant level of chemical feedback during hypercapnia.