2005 OPEN FORUM Abstracts
ALBUTEROL DELIVERY WITH 70%/30% HELIUM/OXYGEN (HELIOX) GAS MIXTURE AS A SOURCE GAS IN THE FLO-MIST CONTINUOUS NEBULIZER
Rockwell Daryl BA RRT, Couture MaryAnn BS RRT, Hartford Hospital, Hartford CT
OBJECTIVE: To evaluate the efficacy of delivering aerosolized bronchodilators continuously using a mixture of 70%/30% Helium/Oxygen (Heliox) as the source gas. Aerosolized bronchodilator therapy has long been the standard of care for resolving acute asthma attacks. Providing bronchodilators in a continuous therapy format is a fairly common practice in severe cases. The use of a Heliox mixture is an accepted therapy due to its less dense properties contributing to a decrease of turbulence in the airways, lowering airway resistance, and further reducing the stimulation of the airways that can contribute to sustained bronchospasm. A medical search of the literature on asthma and Helium/Oxygen therapy provides a number of papers for reference. However, the two treatments, i.e., aerosolized bronchodilators and a Helium/Oxygen mixture, are rarely given simultaneously in part due to lack of equipment that does not provide for its implementation without eliminating or compromising one or both of the two therapies. The Flo-Mist Continuous Medication Nebulizer (Smiths Medical ASD Inc, Wampsville, NY) is FDA- approved to deliver a continuous dosage of medication while providing the option to add a Heliox admixture at 32 L/min as a secondary gas. Research of related articles raise concerns about dilution of medication delivery with this added flow. We hypothesize that the Flo-Mist nebulizer can effectively deliver the amount of drug solution described in the package insert substituting Heliox as the sole source gas in place of oxygen or medical air. In altering the FDA-approved use of the Flo-Mist nebulizer, simplification of the delivery of the two therapies may decrease the amount of equipment required, time to implement, and possibly maximize therapeutic benefits. DESIGN: Multiple comparison studies to assess output of a continuous aerosol delivery system (Flo-Mist) powered only by a 70%/30% Helium/Oxygen mixture. No human or animal subjects were used.
METHODS: Three independent bench tests were performed using 70%/30% Helium/Oxygen mixture and a two-hour solution of 20 mg/hr Albuterol/Normal Saline (a total of 75 cc). In the first two studies, five Flo-Mist continuous nebulizers with 75 cc of solution in each unit were simultaneously run for one hour using Heliox. Following the allotted time (one-hour) a comparative analysis measuring the weight of the remaining solution was performed. In the third study, nine Flo-Mist continuous nebulizers with equal amounts of solution were run independently for one hour and the remaining solution weighed. Each unit was run using the same regulator and flow meter pre-calibrated to flow rates of 13 L/min using a Nellcor Puritan Bennett PS 2000 (Carlsbad, CA). The Flo-Mist is designed for a maximum drive flow of 25 L/min. From the studies performed, we estimated the calculated flow rate of 70/30 Helium/Oxygen set at 13 L/min to be 24.5 L/min. This may indicate the maximum flow rate that can be delivered as the drive gas. Both studies were performed for one hour to eliminate changes in output that occurs with loss of volume as noted in the package insert.
MEASUREMENTS AND RESULTS: Although the flow meter was preset with oxygen to 15 L/min, it was noted that the ball of the Thorpe tube dropped to the 13 L/min reading with Heliox and remained consistent for each sample run. Visualization of output appeared to show a concentration of mist and flow no different than that provided when oxygen was the source gas both with and without the additional titration of Heliox. The mean/standard deviation of the first two studies was 38 ± 4.6 with a SE of 2.07. Using the same regulator and flowmeter for the second study showed a mean/standard deviation of 41.4 ± 2.7 with a SE of 0.79.
CONCLUSION: At 13 L/min., 70%/30% Helium/Oxygen can consistently deliver 40 ml of 20 mg Albuterol solution per hour in the Flo-Mist nebulizer. Further studies are needed to investigate particle size and concentrations of drug delivery using this product.
Acknowledgement: We would like to thank Doug Oberly MS RRT and RF Knauft MD, Hartford Hospital, Hartford, CT, for technical assistance.