Pressurized Metered-Dose Inhalers Versus Nebulizers in the Treatment of Mechanically Ventilated Subjects With Artificial Airways: An In Vitro Study.

Ari, Arzu; Harwood, Robert J; Sheard, Meryl M; Fink, James B

BACKGROUND The primary focus of previous aerosol research during mechanical ventilation was the endotracheal tube (ETT). Consequently, there are limited data in the literature on the delivery of inhaled medications administered with different aerosol devices in mechanically ventilated patients with a tracheostomy tube (TT). The purpose of this study was to quantify and compare the efficiency of aerosol devices in a lung model of an intubated and mechanically ventilated adult with a TT. METHODS An in vitro lung model was constructed to simulate a ventilator-dependent adult with a Portex TT and a Mallinckrodt ETT (8-mm inner diameter). Aerosol was collected distal to the bronchi of an adult mannikin on a filter attached to a passive test lung. A ventilator delivered adult breathing parameters (tidal volume 450 mL, breathing frequency 20 breaths/min, peak expiratory flow 40 L/min, and inspiratory-expiratory ratio 1:3) to the airway. A jet nebulizer and pressurized metered-dose inhaler (pMDI) were placed in the inspiratory limb of the circuit 15 cm from the Y-adapter. The jet nebulizer was operated at 8 L/min to deliver albuterol sulfate (2.5 mg/3 mL), whereas an albuterol pMDI was actuated 4 times with a spacer. Drug was eluted from the filter and analyzed by spectrophotometry. RESULTS Drug delivered via a TT was marginally greater compared with an ETT using the jet nebulizer and pMDI (P = .10 and .046, respectively). Although delivery efficiency with the pMDI was 3-fold greater than with the jet nebulizer with both a TT and an ETT (P = .001 and .002, respectively), the jet nebulizer delivered greater drug mass compared with the pMDI with either a TT (P = .01) or an ETT (P = .005). CONCLUSIONS Aerosol drug delivery via a TT was greater than with an ETT, whereas the delivery efficiency of a pMDI via either airway was greater than that of a jet nebulizer.