Evaluating the delivery of nebulized and metered-dose inhalers in an in vitro infant ventilator lung model

OBJECTIVE: To evaluate drug delivery to the lungs of nebulized and metered- dose inhalers (MDIs) in an in vitro infant lung model. METHODS: An in vitro lung model was modified to study drug delivery. A 1000 mL intravenous bag filled with 500 mL deionized water was attached to a 3. 5 mm(12 cm length) endotracheal tube. An inline Marquest Whisper Jet infant circuit nebulizer system delivered 3.5 mg/3 mt albuterol sulfate inhalatio n solution (Ventolin nebules) at a flow rate of 5 L/min, An Aerochamber (Mo naghan) was placed at the endotracheal tube for the delivery of the MDIs, A lbuterol MDI(Ventolin) 10 inhalations and beclomethasone MDI (Beclovent) 20 inhalations were delivered. A Servo 900C (Siemens-Elma) was used at the fo llowing ventilator settings: positive inspiratory pressure 30 cm H2O), inte rmittent mandatory ventilation 40 breaths/min, positive end expiratory pres sure 4 cm H2O, inspiratory time 0.4 sec. Each formulation was run at least 10 times and assayed in duplicate by HPLC. An unpaired Student's t-test was used to analyze the statistical significance of the data. RESULTS: There was a significantly greater percentage of drug delivery with MDI albuterol (1.96 +/- 0.50) as compared with nebulized albuterol (1.26 /- 0.37) (p = 0.002) or beclomethasone diproprionate (0.51 +/- 0.24) (p = 0 .001). CONCLUSIONS: Albuterol MDI provides a more efficient delivery of drug to th e lune, as compared with nebulized albuterol and MDI beclomethasone dipropr ionate.