MINUTE VOLUME DIVIDER

Typical Number in Hospital: 10

Cost Bands: 3,4

References: 2

This is an open-circuit lung ventilator which derives its power from the pressure of gases delivered to it from a continuous-flow anaesthetic machine. The fresh gas feed must be at least equal to the minute volume requirement of the patient. A minute volume divider normally consists of an elastic or spring-loaded reservoir bag or bellows and a set of valves which allow the contents of the bellows to inflate the lungs at intervals. During the expiratory phase, while the bag is refilling, the patient's expired gases are exhausted to atmosphere.

The cycle time and the inspiratory to expiratory time (I:E ratio) are determined by a mechanism which may depend on time, volume, pressure or flow rate. A separate bellows may be provided to generate a negative pressure during the expiratory phase to draw gas out of the lungs. Examples of minute volume dividers are the Autovent, Minivent, Manley MP2 and Pulmovent, and the Philips AV1 adult/paediatric ventilator.