Evaluation of a prototype expiratory-phase aerosol controller during simulated pediatric volume-controlled...

Some methods of administering aerosolized medications during volume-controlled ventilation require adjustment of ventilator settings to avoid inadvertent increases in tidal volume (VT). Our bench evaluation of an expiratory-phase aerosol controller (EXPAC) sought to determine the differences (1) in aerosol delivery between continuous and EXPAC nebulization in pediatric and neonatal ventilator circuits and (2) in delivered VT with a 30-cm vs a 213-cm nebulizer supply line. DESCRIPTION OF DEVICE: An electrically powered EXPAC linked to the VIP Bird ventilator by a fiberoptic cable and driven by flow from an integral blender was developed to our performance specifications.

In Phase 1, VT was measured at the patient connection under 3 conditions: (1) no nebulizer in-line, (2) a dry in-line nebulizer driven by EXPAC with a 30-cm supply line, and (3) Condition 2 with a 213-cm supply line. In Phase 2, we measured the aerosol delivered to a filter placed between the patient connector and the test lung. Aerosol delivery = filter wet weight-filter dry weight.

(1) When EXPAC was operated according to manufacturer's recommendations, no significant differences were found between VTS measured with EXPAC plus the 30-cm line and with no nebulizer in-line. VT increased significantly (p = 0.0001, 1-way ANOVA) in both circuits with the 213-cm supply line. (2) Mean (SD) aerosol delivery at the patient connection of the pediatric circuit was 1.5 (0.002)% with EXPAC and 1.7 (0.003)% with continuous nebulization (p = 0.23, t test) and of the neonatal circuit 1.6 (0.002)% with EXPAC and 1.5 (0.002)% with continuous nebulization (p = 0.45, t test).

EXPAC eliminated need for adjustment of ventilator settings and according to our data was as effective as continuous nebulization for delivering aerosol to the patient connection.