The Science Journal of the American Association for Respiratory Care

1997 OPEN FORUM Abstracts

AMBIENT NO/NO_{2} LEVELS DURING INO THERAPY WITHOUT EXPIRED GAS SCAVENGING

Bill Phelan RRT, Maine Medical Center Portland, Maine

Standard practice for Inhaled Nitric Oxide programs involves scavenging exhaled gas to keep ambient / background levels of NO & NO_{2} below OSHA specified levels. Anecdotal information suggest that rooms with an air exchange rate of >6x/hr may provide adequate circulation to keep background NO / NO_{2} below these levels. The Occupational Safety & Health Administration [OSHA] limits 8 hour Time Weighted Average [TWA] exposure to 25ppm NO & 5ppm NO_{2}. Short Term Exposure Limits [STEL] are listed at 5ppm NO & 1ppm NO_{2}. We hypothesized that our air handling system would circulate the environment sufficiently to keep background levels of NO & NO_{2} at acceptable levels. A VIP Bird Ventilator (Bird Products, Palm Springs, Ca.) was configured for Time cycled/pressure limited [TCPL] continuous flow ventilation. The total ventilator flowrate was set at 10lpm & 20lpm. Using inspiratory limb titration, 800ppm NO (BOC Gases, Port Allen, La.) was introduced into the circuit via a DelNO 2000 mass flow controller (Sensormedics Critical Care, Yorba Linda, Ca.), resolution 0.01lpm. We utilized a 2030 ft^{3} ICU room with an air exchange rate of 6 exchanges per hour [200 ft^{3}/min]. Circuit gas as well as ambient room air was analyzed using a Sievers 280NOA (Sievers Instruments, Boulder. Colorado) chemiluminescent NO/NO_{2} analyzer, resolution 1ppb. After 2 point calibration of the analyzer, we sampled exhaled gas at a variety of NO & FiO_{2} settings. Gas was sampled at the inspiratory side of the patient wye, as well as at the exhalation valve outlet, and at points 2 ft, 4ft & 7ft from the exhalation valve at a height of 5ft.

Results summarized below: values are expressed in parts per million [ppm]

NO dose 40ppm 20ppm

Vent flow 10 lpm 20 lpm 10 lpm 20 lpm

FiO_{2} 21% 100% 21% 100% 21% 100% 21% 100%

circuit NO_{2} 0.783 1.320 0.831 1.29 0.386 0.479 0.380 0.501

X-valve NO 9.800 9.700 9.100 9.200 3.300 3.400 3.400 3.400

NO_{2} 0.197 0.354 0.224 0.410 0.097 0.186 0.143 0.263

2' out NO 0.113 0.109 0.155 0.147 0.094 0.090 0.116 0.120

NO_{2} 0.087 0.195 0.099 0.227 0.036 0.088 0.039 0.097

4' out NO 0.067 0.060 0.114 0.096 0.038 0.039 0.040 0.041

NO_{2} 0.065 0.089 0.078 0.098 0.044 0.078 0.048 0.089

7' out NO 0.044 0.039 0.067 0.070 0.038 0.038 0.042 0.042

NO_{2} 0.034 0.043 0.039 0.051 0.032 0.034 0.034 0.040

From this data we conclude that, in those patients receiving < =40ppm NO, in rooms with air handling systems with 6 or more exchanges per hour, ambient NO & NO_{2} levels are maintained well below OSHA mandated standards for care giver exposure. Further work examining ambient NO/NO_{2} levels from systems with higher flowrates & NO doses, rooms with less efficient ventilation systems, as well as the implications of exposure to >50 parts per billion NO_{2} may still needed.

OF-97-128

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