The Science Journal of the American Association for Respiratory Care

1999 OPEN FORUM Abstracts

EVALUATION OF OXYHOODS FOR THE DELIVERY OF NITRIC OXIDE

Michael Tracy, RRT, Timothy Myers, RRT, Robert Chatburn, RRT, FAARC University Hospitals of Cleveland, Ohio

BACKGROUND: Typically nitric oxide (NO) is delivered into a closed ventilator circuit ensuring adequate mixing. Injection of NO into an open system like an oxyhood might result in stratification of gases due to differing molecular weights or the production of unacceptable levels of nitrogen dioxide (NO2). The purpose of this study is to determine the feasibility of delivering NO via oxyhoods.

Methods: A 12²´12²´12² hood (Nova Tent House, Nova Health Systems, Blackwood, NJ) with a simulated patient was set up with a 15 L/m flow and FIO2 0.40. The injector module of an INO-vent (INO Therapeutics, Clinton, NJ) was placed on the inlet side of the humidifier. Nine sample lines were suspended inside the hood at the front, middle, back and bottom, middle top positions to sample NO, nitrogen dioxide (NO2) and oxygen. Multiple sample lines were used to prevent sampling inaccuracy caused by repeated opening of the test system. The INO-vent was calibrated according to the manufacturer's instructions. Data were collected for the delivery of 1, 5, 10, 20, and 40 ppm of NO, in that order at each of the nine points in the hood. Each time a new sample line was connected the INO-vent values were allowed to stabilize for 5 minutes before data was collected.

Results: Gas concentrations at various locations are given in the table for 40 ppm NO. These data are shown because they represent the maximum NO2 production and the greatest O2 dilution. In all experimental conditions, the mean difference in gas concentration among all locations was 1ppm. The lowest FIO2 and the highest NO2 were associated with the highest NO concentration.

NO / NO2 ppm back middle front
top 38 / 1.5 38 / 1.5 39 / 1.5
middle 39 / 1.5 39 / 1.5 39 / 1.5
bottom 38 / 1.6 39 / 1.6 39 / 1.5

Conclusions: Injection of NO into an open oxyhood with an FIO2 = 0.40 results in homogenous distribution of NO and acceptable levels of NO2

OF-99-023

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