The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts

PERFORMANCE EVALUATION OF THE HEART CONTINUOUS NEBULIZER

Michael McPeck RRT, Ravi Tandon MD, Kenneth Hughes RRT and Gerald C Smaldone MD PhD. Departments of Respiratory Care and Medicine, SUNY at Stony Brook.

Continuous administration of aerosolized \beta2 agonists has been suggested as an effective treatment for severe reversible airways disease. To facilitate continuous therapy and avoid a feed system for SVNs, the Vortran HEART large volume medication nebulizer was developed. Manufacturer's instructional materials provide scenarios claimed to achieve target drug delivery rates between 5 and 20 mg/hr of albuterol. The goal of this study was to validate drug delivery rate of the HEART nebulizer in the laboratory and compare it against conventional SVNs.

Methods: First, "standing cloud" measurements were conducted on a series of HEART, CIS-US Aero-Tech II and Hospitak PowerMist nebulizers so as to select samples of each that were comparable. Then output studies were conducted on 2 or more comparable samples of each nebulizer using a bench model consisting of an adult aerosol mask on an anatomical face. A to-and-fro adult spontaneous breathing pattern (VT 500 ml, f 20, Insp Time 40%), generated by a sine wave ventilator, was used to "inhale" aerosol through the mouth of the anatomical face. Radiolabeled ^{99m}Tc-albuterol/NS, collected on absolute filters placed distal to the mouth of the face, was used as a tracer to measure Inhaled Mass (the % of the mass of drug or tracer placed in the nebulizer that was actually delivered to the airway opening).

Results: For 3 HEARTs with a 120 ml fill volume, Inhaled Mass averaged only 15.8% after 240 min of operation compared to 34% and 24.9%, respectively, for 2 Aero- Tech II and 2 PowerMist SVNs with 3 ml fill volumes that all ran dry at 8 min. The actual drug delivery rate of the HEART in the 5, 10, 15 and 20 mg/hr scenarios is only 0.79, 1.58, 2.36 and 3.16 mg/hr respectively. Conclusion: The HEART nebulizer did not deliver the target dose specified by the manufacturer. It appears that gravimetric techniques used accurately by the manufacturer to measure the HEART's liquid nebulization rate were extrapolated erroneously to predict drug delivery rates. Data from typical SVNs suggest that greater drug delivery hourly rates could be achieved with continuously or intermittently filled SVNs than with the HEART nebulizer. Nebulizer output performance over time is best expressed by Inhaled Mass %.

OF-95-195

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