Accuracy of delivered versus preset minute ventilation of portable emergency ventilators

Abstract

The accuracy of delivered minute volume (E) ventilation of portable emergency ventilators (PEV) was evaluated. Five PEV from three manufacturers were adapted to an artificial lung for varying compliance and resistance. Each PEY was tested in the “no airmix” (pure oxygen) and “airmix” (approximately 60% oxygen) setting at different frequencies and YE. Measurement of delivered E (VE_del) was made using a pneumotachograph and digital integration of the flow values > 1 min (maximal error ± 2%). Maximal inspiratory pressure (P_insp) was measured with a transducer.

Two PEY from one manufacturer produced severe hyperventilation when used at low YE (i.e., in children). Two other PEV from another manufacturer produced less marked hyperventilation, but revealed unexpected hypoventilation during conditions of higher inspiratory pressures (i.e., in adults with reduced compliance). The prototype PEY that was tested also revealed less marked hyperventilation with small decreases (down to −10% of the E at higher P_insp values). Further investigation is needed before this prototype goes into production.

Manufacturers should redefine predicted values or machine settings or indicate that use of these devices may produce results which are not in accordance with the machine settings. Until adjustments are made, ventilation should be monitored when possible by measurement of end-tidal Pco₂ or systemic arterial blood gases.