Aerosol Delivery During Continuous High Frequency Oscillation for Adult and Pediatric Patients Receiving Invasive Ventilation

Abstract

Background: Continuous high-frequency oscillation (CHFO) of the airway has been reported to improve secretion clearance and lung expansion. The device also provides continuous aerosol using a jet nebulizer (JN). Concomitant aerosol therapy during CHFO is appealing during invasive ventilation. However, evidence on the efficiency of aerosol delivery is rare. We investigated the aerosol delivery efficiency with Metaneb during invasive ventilation in both adult and pediatric settings, and explored methods to improve efficiency. Methods: A model lung (TTL, Michigan Instruments) was connected to an ICU ventilator (PB840, Medtronic) via endotracheal tubes (ETT) of 8.0mm, 6.0mm, and 5.0mm respectively to simulate adult (COPD and healthy), and pediatric (5 and 10 y old) patients. Tidal volume was set at 6 mL/kg for all scenarios and frequencies were 16 breaths/min, except the 5 y-old patient (20 breaths/min). A collecting filter was placed between ETT and the model lung. Metaneb was set at high frequency oscillation with low flow. A vibrating mesh nebulizer (VMN, Aerogen) was placed at the inlet of humidifier vs between ETT and Y-piece. Albuterol (2.5mg in 3mL) was nebulized for each condition (n = 3). Drug was eluted from the filter and assayed with UV spectrophotometry (276 nm). Results: With CHFO during invasive ventilation, inhaled dose with JN at its manifold position was low in both adult (1.52 ± 0.44 %) and pediatric (0.86 ± 0.05 %) patients; substituting VMN for JN increased inhaled dose: VMN placed at the inlet of humidifier vs between ETT and Y-piece in adult (13.35 ± 1.01 vs 7.17 ± 0.23%, P = .004) and pediatric patients (7.79 ± 2.46 vs 4.21 ± 0.70 %, P = .004). Regardless of VMN placement, inhaled dose with CHFO was lower than inhaled dose with VMN without CHFO [22.66 (19.54, 25.44) vs 7.19 (5.11, 11.61) %, P < .001]. Conclusions: Using Metaneb per label to deliver aerosolized medication during invasive ventilation was inefficient for both adult and pediatric patients. Vibrating mesh nebulizer during CHFO improved inhaled dose, but still lower than standard practice without CHFO.