COMPARISON OF TOTAL RESISTIVE WORK OF BREATHING IN 2 GENERATIONS OF VENTILATORS IN AN ANIMAL-MODEL

Spontaneous breathing through an endotracheal tube and ventilator circ uit is associated with an increased work of breathing (WOB). Recently, pediatric ventilators have introduced improved features to optimize p atient-ventilator interactions; We performed an experiment utilizing a n animal model to compare total resistive WOB of two widely used venti lators, the Siemens Servo Ventilator 300 (SV300) with patient-optimize d features, such as flow-triggering and rapid response time, and the S iemens 900C (S900C) without those features. A total of 120 experiments of 10 minutes duration each were performed in 6 anesthetized. Intubat ed lambs. in each experiment, the animal was randomized to either pres sure support ventilation (PSV) of 5 cm H2O, or continuous positive air way pressure (CPAP) with 0 cm H2O end expiratory pressure (ZEEP) while supported by the SV300 or the S900C. Each animal was used as its own control. WOB was measured with a Bicore monitoring device as WOB of th e animal (WOBp), WOB of the ventilator (WOBv), and the pressure time p roduct (PTP) for each breath during the experiment. Oxygen consumption (Vo(2)) of the animal was measured using breath-by-breath gas analysi s with a customized metabolic monitoring system. A Wilcoxon signed ran k sum test was used for analysis. All comparisons between the ventilat ors for both CPAP and PSV showed a statistically significant differenc e (p < 0.001). WOBp was reduced by 47% during pressure support ventila tion (PSV) and by 47% during CPAP when the SV300 was used compared to the S900C. We conclude that WOB is significantly lower in animals vent ilated with the SV300 than with the S900C ventilator, and we speculate that ventilators with the features of the SV300 may offer advantages in ventilating pediatric patients. (C) 1996 Wiley-Liss, Inc.