The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

IMPROVING AEROSOL DELIVERY TO INFANTS DURING NASAL CPAP: AN IN VITRO MODEL.

James B. Fink, MS, RRT, FAARC, Prashant Kakade. Aerogen, Inc., Mountain View, CA.

Background:
Historically, aerosol delivery to pre- and near-term infants by nebulizers has been inefficient with less than 1% deposition, on or off the ventilator (Fink, Resp Care 2004). Aerosol delivery to infants using nasal continuous positive airway pressure (CPAP) has not been reported using high efficiency aerosol delivery systems. We created an in vitro model of infant ventilation during nasal CPAP to compare the efficiency of two aerosol delivery devices, the Aeroneb® Professional Nebulizer System (Aeroneb Pro) and a low volume prototype Pulmonary Drug Delivery System (PDDS) suitable for placement proximal to the infants airway. Both devices incorporate Aerogen’s OnQ™ micropump aerosol generator. A secondary objective was to differentiate delivery of aerosol vs condensate to the infant model.

Methods:
A lung simulator, consisting of an adapter with orifices representing infant size nares connected to an absolute filter, attached to a reciprocating pump animal ventilator (Harvard Apparatus), was set to infant ventilatory parameters (VT 10 mL, resp rate 40 bpm). A constant air flow of 10 lpm was used to generate a CPAP of 5 cm H2O. Albuterol sulfate (0.5 mL; 0.5%) was aerosolized with an Aeroneb Pro placed in the inspiratory limb of the CPAP circuit, and with a PDDS nebulizer placed between the main flow of the CPAP circuit and the nasal prongs (n=3). To differentiate between aerosol and condensate delivery to the filter, an additional run with the PDDS was performed with the filter placed above the nasal prongs (n=5). Drug was collected on a filter placed distal to the nasal prongs, and assayed using HPLC.

Results:
Using the Aeroneb Pro® in a standard position in the CPAP circuit, deposition (mean ± SD) was 1.3±0.8%. The PDDS delivered 22.5 ± 1.7% with filter at the level of the prong adapter, and 12.8±2.7% when filter was placed superior to the nasal prongs.

Conclusions:
The PDDS delivered an order of magnitude more albuterol through the nasal prongs during CPAP than the Aeroneb Pro when placed in typical orientation. The Aeroneb Pro has previously been shown to be more efficient than standard nebulizers in an animal model of infant ventilation, with > 13% deposition (Dubus, AJRCCM 2003). Still, deposition in the inspiratory limb of the CPAP system was relatively low compared to the PDDS. Data from placement of the filter superior to the nasal prongs suggests that up to 40% of the albuterol delivered with the model in a standard orientation may be condensate vs aerosol. The high efficiency delivery of aerosol to a nasal CPAP infant model suggests future opportunities for administration of active medications to the airways of infants.

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