Infant ventilator design: performance during expiratory limb occlusion.

We examined the specifications and design of the inspiratory pressure regulating valve of 8 continuous flow, pressure-limited infant ventilators. Two pressure regulating designs are currently available; one placing the primary pressure regulating valve on the inspiratory limb, the other placing it on the expiratory limb. Seven ventilators incorporate the latter design to limit inspiratory pressure and must have a safety pressure-relief valve located on the inspiratory limb to vent pressure in case of circuit occlusion. These pressure-relief valves are generally set by the manufacturer far in excess of pressures normally used for infant ventilation. Alarm systems are often absent or inadequate to warn of high pressure conditions during circuit obstruction. A case report detailing the fatal complication of prolonged excessive airway pressure during circuit occlusion is presented. Improvements in the pressure-relief valve designs currently available are possible, and may be necessary to provide adequate protection from barotrauma. The majority of infant ventilators currently available expose the patient to unnecessary excessive airway pressures in the case of expiratory limb occlusion, and the lack of alarm systems may leave the operator unaware of malfunction.