Abstract
By a microcomputerized ventilator system with feedback loops for flow(V) and pressure(P) it was possible to generate a positive P during inspiration and a negative P during expiration in a constant proportion to the instantaneous V of spontaneous breathing. The ratio P/V represents a negative ventilator resistance(NVR), is adjustable (0-15 kPaxs/l) and produces a resistive unloading of the respiratory system. We found a strong linear correlation between the NVR and the resultant drop in transpulmonary resistance (39 trials in 8 rabbits after intra- or extrapulmonary airway obstruction, r=0.93, p<0.001). Similarly, there was a close relationship between the NVR and the decrease in inspiratory resistive work per tidal volume of spontaneous breathing (n=39, r=0.85, p<0.001). If NVR exceeded the total resistive load of the respiratory system, the combined ventilator-ETtube-patient-system started to oscillate continuously near its resonant frequency(RF) as it was no longer damped. Oscillatory amplitudes and mean airway pressure were controlled independently of each other. This new principle proved useful for high frequency ventilation in rabbits with normal (n=5, RF=4-6Hz) and surfactant deficient lungs (n=5, RF=6-10Hz).
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Schulze, A., Scnaller, P., Behchardt, B. et al. 110: AN INFANT VENTILATOR TD PROVIDE HIGH FREQUENCY VENTILATION NEAR THE RESONANT FREQUENCY OF THE RESPIRATORY SYSTEM. Pediatr Res 24, 279 (1988). https://doi.org/10.1203/00006450-198808000-00135
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DOI: https://doi.org/10.1203/00006450-198808000-00135