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.