Understanding and operating the Bennett MA-1 ventilator. Tips on adjusting the controls to avoid problems.

The Bennett MA-1 ventilator is a volume-cycled, constant flow generator that can act as an assistor, controller, or assist-controller. It is one of the most commonly used ventilators in clinical practice. With this unit, inspiration continues until a preset tidal volume is delivered to the patient--unless impedances to gas flow increase system pressures to a preselected limit. Thus, setting the maximum inspiratory pressure too low limits the ability of the ventilator to deliver the tidal volume, causing it to function as a pressure-cycled device. Other basic controls allow you to establish the sensitivity of the ventilator to spontaneous breathing attempts, the maximum flow rate, the frequency of respirations, and the oxygen percentage. Special controls permit delivery of a sigh breath and slowing of exhalation.