Aerosol delivery during continuous nebulization.

BACKGROUND AND OBJECTIVES Continuous administration of aerosolized beta 2-agonists has been suggested as an effective treatment for severe reversible airways disease. To facilitate continuous therapy and avoid a feed system for small-volume nebulizers (SVNs), a large-volume medication nebulizer (Vortran HEART) was developed. The goal of this study was to determine actual drug delivery of the HEART and conventional SVNs for both adult and pediatric breathing patterns. DESIGN Output studies were conducted on comparable samples of CIS-US AeroTech II and Hospitak PowerMist SVNs and Vortran HEART large-volume continuous nebulizers. To duplicate clinical aerosol delivery via an aerosol mask, drug particles were inhaled through the mouth of a model of a human face for two test breathing patterns (adult = tidal volume (Vt) of 500 mL, 20 breaths/min, duty cycle of 40%; pediatric = VT of 100 mL, 35 breaths/min, duty cycle of 40%), generated by a ventilator. Radiolabeled particles of saline solution, confirmed to behave identically to albuterol, were collected on absolute filters at the mouth of the face to measure the actual mass of albuterol particles delivered to the airway opening. RESULTS The AeroTech II and PowerMist SVNs delivered 5.14 and 3.74 mg/h, respectively, for the adult breathing pattern and 2.97 and 2.48 mg/h, respectively, for the pediatric breathing pattern. Drug delivery rates of the HEART were a function of drug concentration and ranged from 0.87 to 3.48 mg/h for the adult breathing pattern. For the pediatric breathing pattern, drug delivery rate was a function of drug concentration and inspired minute ventilation and ranged from 0.41 to 1.83 mg/h. CONCLUSION Our data demonstrate that drug delivery to the patient, expressed as inhaled mass over time, is similar for continuous nebulization (HEART system) and intermittently filled SVNs. In addition, for all nebulizers, the influence of the pediatric breathing pattern needs to be considered. Continuous nebulization permits the redistribution of health-care personnel and may reduce the costs of therapy.