Albuterol Delivery via In-Line Intrapulmonary Percussive Ventilation Superimposed on Invasive Ventilation in an Adult Lung Model

BACKGROUND: Intrapulmonary percussive ventilation (IPV) is frequently used for airway clearance, together with delivery of aerosolized medications. Drug delivery via IPV alone increases with decreasing percussion frequency and correlates with tidal volume ( V T ), whereas drug delivery via IPV during invasive ventilation is not well characterized. We hypothesized that drug delivery via IPV–invasive ventilation would differ from IPV alone due to control of ventilation by invasive ventilation. METHODS: An adult ventilator circuit was used for IPV–invasive ventilation. A normal or a diseased lung model was configured to airway resistance of 5 cm H 2 O/L/s and lung compliance of 100 mL/cm H 2 O or to airway resistance of 20 cm H 2 O/L/s and lung compliance of 50 mL/cm H 2 O, respectively. The ventilator settings were the following: pressure control continuous mandatory ventilation mode, 10 breaths/min; PEEP, 5 cm H 2 O; F IO 2 , 0.21; inspiratory time, 1 s; no bias flow; and inspiratory pressure, 10 or 15 cm H 2 O for the normal or the diseased lung model, respectively, to reach V T 500 mL with IPV off. Albuterol nebulized from an IPV device was captured in a filter placed before the lung model and quantitated by spectrophotometry. RESULTS: The maximum efficiency of albuterol delivery via IPV–invasive ventilation was not different from that via IPV alone (mean ± SD of loading dose, 3.7 ± 0.2% vs 4.2 ± 0.3%, respectively; P = .12). The mean ± SD albuterol delivery efficiency with IPV–invasive ventilation was lower for the diseased lung model versus the normal model (1.6 ± 0.3% vs 3.2 ± 0.5%; P < .001), which increased with decreasing percussion frequency. In contrast, the mean ± SD V T was lower for the normal lung model versus the diseased model (401 ± 14 mL vs 470 ± 11 mL; P < .001). CONCLUSIONS: Albuterol delivery via IPV–invasive ventilation was modulated by percussion frequency but was not increased with increasing V T . The delivery efficiency was not sufficiently high for clinical use, in part due to nebulizer retention and extrapulmonary deposition.