A programmable inspiratory flow generator for aerosol bolus delivery

Abstract

A microcomputer-controlled system that generates a discrete digital approximation of a desired inspiratory flow profile is described. Discrete flows between 0 and 387.5 ml/s can be achieved in increments of 12.5 ml/s with five solenoid valves. This pneumatic digital-to-analog converter is coupled to a mixing apparatus so that boluses of aerosol can be delivered at precise moments during an inspired breath. Between bolus deliveries, the system provides maintenance ventilation and allows flow pattern, tidal volume, inspiratory-to-expiratory time ratio, and respiratory rate to be programmed as desired.