In vitro evaluation of aerosol bronchodilator delivery during noninvasive positive pressure ventilation:: Effect of ventilator settings and nebulizer position

Objective: Respiratory failure due to exacerbation of obstructive lung disease has been successfully treated with noninvasive positive pressure ventilation (NPPV). However, there have been no reports of factors affecting aerosol delivery during NPPV. Our objective was to determine the effect of ventilator settings and nebulizer position on albuterol delivery during NPPV. Design: Bench model study. Setting: University laboratory. Subjects: None. Interventions: A Respironics BiPAP S/T-D30 with a standard circuit was attached to a lung model simulating spontaneous breathing. Inspiratory/expiratory pressures of 10/5, 15/5, 20/5, 15/10, 20/10, and 25/10 cm H2O were tested at respiratory rates of 10 and 20/min. A nebulizer was filled with 5 mg of albuterol in 4 mL of solution, driven with 8 L/min oxygen, and placed at either a proximal (ventilator outlet) or distal (between leak port and lung model connection) position. Albuterol delivery was estimated by measuring the amount of the albuterol collected on a filter placed at the inlet of the lung model. Measurement and Main Results: Albuterol delivery varied from 5.2 +/- 0.4% to 24.5 +/- 1.3% of the nominal dose and was significantly affected by the position of the nebulizer, respiratory rate, and BiPAP settings (p <.001 in each case). The greatest albuterol delivery was observed with the nebulizer operating at the distal position and a respiratory rate of 20/min. At this respiratory rate and nebulizer placement, albuterol delivery increased with increasing inspiratory pressure levels and decreased as expiratory pressure levels were increased. Nebulizer flow did not affect function of the ventilator. Conclusions: At optimum nebulizer position (between the leak port and patient connection) and ventilator settings (high inspiratory pressure and low expiratory pressure), as much as 25% of the nominal albuterol dose may be delivered during NPPV.