Pressure-time relationships of pressure-limited neonatal ventilators.

A pressure-limited ventilator (Bourns BP-200, Anaheim, CA) and a simple, manually operated constant flow ventilator were studied using a commercially available infant lung simulator (Bourns LS-130, Anaheim, CA). The characteristics of inspiratory pressure-time relationships during ventilation with these ventilators were analyzed. The analytic properties of the inspiratory phase of the pressure-time curve were related to simulator resistance and compliance. A mathematical model was constructed relating the initial rapid rise of the pressure curve to simulator resistance and the subsequent slope of the curve to simulator compliance. Qualitatively similar tracings were obtained with the BP-200 during normal ventilation, with simulated airway obstruction and thoracic restriction. These findings suggest that monitoring pressure-time relationships may be useful in the qualitative assessment of resistance and compliance during pressure-limited ventilation of neonates.