The Science Journal of the American Association for Respiratory Care

1997 OPEN FORUM Abstracts

SMALL VOLUME NEBULIZERS ARE INEFFECTIVE WHEN USED IN-LINE WITH HIGH FLOW OXYGEN THERAPY.

J. Dhaliwal RRT, K. Jager RRT, M. Tweeddale MD. Vancouver Hospital & Health Sciences Center, Vancouver, Canada

Introduction: Bronchodilators are commonly administered through small volume nebulizers (SVN) placed in-line with a high O_{2} flow. This study was designed to determine the efficacy of SVN treatment when given in-line with high flow O_{2}. Methods: A 2-chamber test lung was used to simulate a spontaneously breathing non-intubated patient. Simulated parameters were tidal volume 500 ml and rate 20/min, at inspiratory flowrates of 40 and 80 L/min. An aerosol mask was adapted to fit a filter which was connected to the 'patient' chamber of the test lung. All tests were made at both inspiratory flowrates, using 4 filters for each test. For each test, 5 ml normal saline were nebulized from a SVN using a driving flow of 8 L/min for 7 min, the filter being weighed before and after to determine the amount of saline which would have reached the test lung. Tests were repeated with the SVN in-line with high flow O_{2} at 42 and 67 L/min, corresponding to an FiO_{2} of 0.40 and 0.70.

Results: Mean aerosol deposition (±SD) in the filters is recorded below.

Patient SVN 8 L/min alone 42 L/min (0.40) 67 L/min (0.70)

flowrate (O_{2} flow) (O_{2} flow)

40 L/min ^0.69 ± 0.03 g *0.07 ± 0.02 g *-0.07 ± 0.02

80 L/min 0.61 ± 0.02 g *0.04 ± 0.00 g *-0.08 ± 0.01

^ p < 0.05 vs SVN alone at 80 L/min, * p < 0.001 vs SVN alone

Conclusion: Both patient and O_{2} flow factors influence aerosol deposition using SVN's. High flow O_{2} effectively prevents aerosol delivery from the SVN to the patient. Therefore SVN's should not be used in-line with high flow oxygen.

OF-97-097

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