EFFECTS OF VARYING INSPIRATORY FLOW WAVEFORM AND TIME IN INTERMITTENT POSITIVE PRESSURE VENTILATION - PULMONARY-EDEMA

Greyhound dogs were given oleic acid i.v. to induce controlled pulmonary edema. These animals were then studied using intermittent positive pressure ventilation (IPPV) with 4 different inspiratory flow waveforms, each at 3 different inspiratory times, in a fixed respiratory cycle of 4 s at a constant tidal volume. Although there were statistically significant differences in airway and esophageal pressures between the different waveforms, and times , there was little variation in the other physiological parameters studied except for arterial CO2 tension (PaCO2) which showed statistically significant improvement with reversed ramp and sine wave inputs and at the longer inspiratory time of 2.2 s. Venous admixture (.ovrhdot.Qs/.ovrhdot.Qt) was also less with the longer inspiratory time of 2.2 s.