THE EFFECT OF THE LEVEL OF VENTILATORY ASSIST ON THE LEVEL OF RESPIRATORY DRIVE IN DECEREBRATE CATS

The present study was undertaken to investigate whether, independent o f changes in Pa-CO2, ventilatory assist influences not only the patter n but also the level of the respiratory drive. The experiments were pe rformed on decerebrate and paralyzed cats ventilated by a phrenic-driv en servo respirator at three different FICO2 levels (0, 0.03, 0.05). T he level of ventilatory assist was altered within the range where Pa-C O2 did not exceed 80 Torr. A higher FICO2 accompanied a higher level o f ventilatory assist. The relationship between the minute phrenic acti vity and log(10) Pa-CO2 at a given FICO2 was linear. No significant di fference was found in the regression lines at different levels of FICO 2. We conclude that ventilatory assist has little effect on the respir atory drive at a constant level of chemical feedback during hypercapni a. (C) 1997 Elsevier Science B.V.