2005 OPEN FORUM Abstracts
ALBUTEROL DELIVERY DURING HIGH FREQUENCY OSCILLATORY VENTILATION USING A MDI WITH A SPACER IN A NEONATAL VENTILATOR-LUNG MODEL.
Marlow Hanson PharmD, John Davidson RRT-NPS, James Keenan BS RRT-NPS FAARC, John Sweeley J, Donald Null MD, Robert Ward MD, Ralph A. Lugo PharmD. University of Utah College of Pharmacy and School of Medicine, Primary Children's Medical Center, Salt Lake City, Utah.
Introduction: Albuterol is often administered to neonates during high frequency oscillatory ventilation (HFOV) for severe lung disease. The site of administration within the circuit for optimal lung delivery has not been thoroughly investigated. Visual observation following actuation with a metered dose inhaler (MDI) at any location suggests significant aerosol loss through the expiratory limb of the ventilator circuit. Some facilities that use Ballard suction catheters disconnect the sheathed catheter and use this site to actuate the MDI into a spacer to avoid breaking the circuit and thus preventing derecruitment. It is theorized that a venturi effect from the oscillatory mechanics may enhance drug delivery at this site. The objective of this bench study was to measure the amount of aerosolized albuterol delivered to a neonatal lung-model under various conditions of HFOV using a MDI with an ACE spacer (DHD Health Care) placed at the Ballard suction catheter site.
Methods: A neonatal lung-model was attached to a 3.0mm endotracheal tube (ETT), ventilated with a high frequency 3100A SensorMedics oscillator. The proximal end of the ETT was fitted with the "Y" type Ballard suction catheter. A filter was placed distal to the ETT to trap aerosolized albuterol delivered to the test lung. An ACE spacer was adapted to fit the sheathed catheter site. The opposite end of the ACE was capped. The following ventilator settings were tested: 1) MAP=12 cm H20, amplitude=15 cm H20; 2) MAP=20 cm H20, amplitude=30 cm H20. Ten replicates were conducted for each experimental condition. Each experiment was run in a humidified circuit at 36°C. Albuterol deposited on the filter was quantitatively analyzed by high pressure liquid chromatography (HPLC) and reported as percent of actuated dose.
Results: Mean albuterol delivery onto the filter was 0.24±0.17% for oscillator settings 1 and 0.07±0.02% for oscillator settings 2.
Conclusions: Delivery of aerosolized albuterol through an ACE spacer placed at the Ballard suction catheter site is highly inefficient during HFOV. On visual inspection, albuterol aerosol appeared to be lost through the expiratory limb of the oscillator circuit. Furthermore, the theory that a venturi effect from the oscillatory mechanics enhances drug delivery at this site cannot be supported by this study. This bench model suggests that albuterol aerosol delivered by MDI and ACE to a premature neonate on HFOV results in very limited drug delivery to the patient.