The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

EVALUATION OF THE INOVENT FOR DELIVERY OF LOW DOSE INHALED NITRIC OXIDE VIA NASAL CANNULA AT LOW FLOWS

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

BACKGROUND: Inhaled nitric oxide (iNO) is a selective pulmonary vascular smooth muscle relaxant. Typically iNO is delivered via ventilator circuit. Previous work at our institution (Resp Care 1999; 44(10)) demonstrated low dose iNO could safely and effectively be delivered via oxyhood. Work by Newhart et al (Resp Care 1999; 44(10)) demonstrated that iNO could be delivered with the INOvent (Datex-Ohmeda, Madison WI) adapted to a nasal cannula (flow 2-8 L/min, NO 20-40ppm). This method of iNO delivery has been proposed for use in a neonatal/pediatric setting. The purpose of this study was to determine the accuracy of iNO dosages delivered via neonatal and pediatric cannulas at flows below the specified minimum.

Methods: Oxygen from a flowmeter and humidifier was directed through the INOvent injector module. The output side of the injector module was fitted with a six inch section of 22 mm ID corrugated tubing as a mixing chamber. An INOvent sample tee was attached to the corrugated tubing. This provided for both gas sampling and output to either a neonatal or pediatric cannula (Salter Labs, Arvin, CA). After the INOvent was calibrated according to the manufacturer's instructions, it was set to deliver 1-10 PPM through the cannula at flow rates of 0.75 or 1.5 L/min. The delivered NO concentrations analyzed with the INOvent were compared to measurements from a reference analyzer (Sievers 280 NOA, Sievers, Boulder, Colorado). Measurements were made three times at each combination of flow and cannula size.

Results: Initial readings for all experiment conditions were extremely unstable on both analyzers. This problem was resolved after the injector module was fixed in the vertical position to the INOvent handrail with flow directed upward. The error in delivered NO concentration was similar for all conditions and proportional to the setting. The actual concentration was consistently above the set value. Representative data are shown below (mean with 95% confidence intervals) for the neonatal cannula at 1.5 L/min.

Conclusions: There is significant error (up to 50%) in the set NO concentration when using flows below manufacturer's specifications. We recommend against using the INOvent to deliver nitric oxide to infants through a nasal cannula. (See Original for Figure)

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