Ventilator-integrated jet nebulization systems: tidal volume control and efficiency of synchronization

Jet nebulizers constitute the aerosolization devices most frequently used during mechanical ventilation. Continuous nebulization can influence the delivered tidal volume (V(T)) and lead to significant medication loss during expiration. Ventilators thus provide integrated jet nebulization systems that are synchronized during inspiration and ostensibly keep VT constant.

This was a bench study of systems integrated in the Evita XL, Avea, Galileo, and G5 ventilators. The VT delivered with and without nebulization, the inspiratory synchronization of nebulization, and the aerosol deposition were measured with 2 locations of the nebulizer.

Changes in V(T) with the nebulizer were below 20 mL and below 10% of set V(T) for all ventilators. Synchronization was good at the beginning of insufflation, but prolonged nebulization was observed with all ventilators at the end of insufflation, until up to 1 s during expiration: 5-80% of nebulization occurred during expiration with significant aerosol loss in the expiratory limb. Synchrony could be improved by (1) reducing gas compression/decompression phenomena proximal to the jet nebulizer and (2) increasing inspiratory time, which reduced the amount of nebulization occurring during expiration. Placing the nebulizer upstream in the inspiratory limb did not affect inspiratory synchrony but allowed reduction of the amount of aerosol lost in the expiratory limb.

Jet nebulizer systems integrated in the tested ventilators are reliable in terms of V(T) control. Gas compression in tubing driving gas to the nebulizer delays synchronization and reduces nebulization yield if the nebulizer is placed close to the Y-piece. Increasing inspiratory time with no end-inspiratory pause reduces the expiratory loss of medication if placement of the nebulizer upstream in the inspiratory limb is not feasible.