Aerosol Delivery via Continuous High-Frequency Oscillation During Mechanical Ventilation

BACKGROUND: As the use of continuous high-frequency oscillation combined with nebulization during mechanical ventilation becomes more prevalent clinically, it is important to evaluate its aerosol delivery efficacy.

METHODS: A bench study was conducted that simulated 2 adult and 2 pediatric conditions. A continuous high-frequency oscillation device integrated into the inspiratory limb of a conventional critical care ventilator was attached to an endotracheal tube (ETT) with a collection filter and test lung. High-frequency oscillation with high-flow setting was used with jet nebulizers attached to the manifold, and a vibrating mesh nebulizer placed between the ETT and the ventilator circuit versus at the inlet of the humidifier. Albuterol (2.5 mg in 3 mL) was nebulized for each condition (no. = 3). The drug was eluted from the collection filter and assayed with ultraviolet spectrophotometry (276 nm).

RESULTS: During continuous high-frequency oscillation, the mean inhaled dose with jet nebulizers was low (<2% with the adult settings and <1% with the pediatric settings). Across both adult and pediatric conditions, when the vibrating mesh nebulizer was placed between the ETT and the Y-piece during continuous high-frequency oscillation, the inhaled dose was higher than with the placement of the vibrating mesh nebulizer at the inlet of the humidifier, median 11.1% (IQR 7.0%–13.7%) median 6.0% (IQR 3.9%–7.2%) (P = .002) respectively, but still lower than the inhaled dose with the vibrating mesh nebulizer placed at the inlet of the humidifier with continuous high-frequency oscillation off, median 22.7% (IQR 19.5%–25.4%) versus median 11.1% (IQR 7.0%–13.7%) (P < .001). The inhaled dose with the 10-year-old scenario was higher than with the 5-year-old scenario in all settings except aerosol delivery via continuous high-frequency oscillation.

CONCLUSIONS: During invasive mechanical ventilation with continuous high-frequency oscillation, aerosol delivery with jet nebulizers in the manifold resulted in a marginal inhaled dose. The vibrating mesh nebulizer at the ETT during continuous high-frequency oscillation delivered 6-fold more aerosol than did the jet nebulizer, while delivering only half of the inhaled dose with the vibrating mesh nebulizer placed at the inlet of the humidifier without continuous high-frequency oscillation.