FACTORS INFLUENCING INDOOR CONCENTRATIONS OF NITRIC-OXIDE IN A PARISIAN INTENSIVE-CARE UNIT

In low concentrations, inhaled nitric oxide (NO) increases arterial ox ygenation in patients with severe acute respiratory distress syndrome. When present in the ambient atmosphere, NO and its oxidative derivate , nitrogen dioxide (NO2), are considered pollutants. The aim of this s tudy was to assess whether the administration of inhaled NO to mechani cally ventilated patients was associated with an increased risk of exp osure to NO and NO2 for medical and paramedical staff. During a 1-yr p eriod, indoor and outdoor NO and NO2 concentrations were measured usin g chemiluminescence in a 14-bed intensive care unit (ICU) to assess th e possible influence of therapeutic NO administration on indoor pollut ion. Ambient concentrations of NO within the ICU were 237 +/- 147 part s per billion (ppb) during periods of NO administration and 289 +/- 14 7 ppb during periods without NO administration (mean +/- SD, NS). Indo or concentrations of NO and NO2, were entirely dependent on outdoor co ncentrations and were mainly influenced by climatic conditions such as atmospheric pressure, mass of clouds, and speed of the wind. Therapeu tic administration of concentrations of inhaled NO less than or equal to 5 ppm to critically ill patients did not affect the ambient concent ration of NO and NO2 within the ICU, which was mainly dependent on the outdoor air pollution. As a consequence, scavenging of exhaust NO fro m the breathing circuit in the ventilator does not appear mandatory in ICUs located in areas with significant urban pollution when NO concen trations less than or equal to 5 ppm are administered.