The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

NITRIC OXIDE (NO) VIA NASAL CANNULA

K. Boyle, MS, RRT, G. Lowe, BS, RRT, Richard James, Arkansas Children's Hospital, Little Rock, AR

Background: The Cardiology physicians requested that we find a way to safely deliver NO to non-intubated patients. During cardiac catheterization, it may be desirable to administer NO for a short period of time to determine if a non-intubated patient will respond to the NO. We decided to investigate the safety of delivering NO via NC since we had had reports of problems with staff when delivering it through hoods.

Methods:
A NO delivery system was designed to allow mixture of O2 and NO through a "wye" adapter. NO and Nitrogen Dioxide (NO2) analyzers (Dräger) were adapted to fit into the system for continuous monitoring, and a nasal cannula (NC) was connected on the outflow side of the analyzers (see diagram below):
This was a bench test; no patient or animal was involved in the study. NO tank concentration was 800 ppm. The system ran for 8 hours in an empty patient room, O2 flow was 2.5 lpm, NO flow was <.1 lpm (<100 ml/min) with a target NO concentration of 40 ppm. At the time of the study, this was felt to be the maximal concentration that would be utilized with this method of delivery. Two environmental air sampling tubes were placed in the room, one 2 feet from the nasal prongs and one 5 feet from the nasal prongs. The air sampling tubes were changed out at hour 4 and replaced with 2 new ones at the same distances. NO2 and NO readings, NO psig, ppm, and flow were recorded at close to 30-minute intervals. The air temperature of the room was 70 degrees, and the room underwent 6 air exchanges per hour. A laboratory accredited by the American Industrial Hygiene Association, Clayton Environmental Consultants, performed the air sampling tube analysis.

Results:
The levels for nitric oxide and nitrogen dioxide were less than the detection limit of the laboratory (0.3 ppm), and did not exceed the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit or the American Conference of Governmental Industrial Hygienist (ACGIH) threshold limit value. The NO tank psig went from 1200 to 1140 over the 8-hour period, NO2 levels read from a low of 3.0 to a maximum of 3.8. Discussion: In order to assess the pulmonary vascular response in non-intubated patients, NO was blended and administered via NC to obtain an NO concentration of 40 ppm. The results obtained indicated the NO and NO2 were undetectable for this concentration. Since a patient was not attached to the system, and not absorbing the NO; the undetectable limits would be further reduced with a patient utilizing the system and absorbing the gases. It is our belief that NO administered via NC is a safe and effective method of assessing pulmonary vascular response in non-intubated patients. (See Original for Figure)

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