AIR CONTAMINATION WITH NITRIC-OXIDE - EFFECT ON EXHALED NITRIC-OXIDE RESPONSE

This study examines the response of exhaled nitric oxide (NO) concentr ation (ECNO) and quantity of exhaled NO over time (EVNO) in 10 healthy subjects breathing into five polyethylene bags, one in which syntheti c air was free of NO and four in which NO was diluted to concentration s of 20 +/- 0.6, 49 +/- 0.8, 98 +/- 2, and 148 +/- 2 ppb, respectively . Each subject was connected to each bag for 10 min at random. Minute ventilation and ECNO were measured continuously, and EVNO was calculat ed continuously. ECNO and EVNO values were significantly higher for an inhaled NO concentration of 20 ppb than for NO-free air. Above 20 ppb , ECNO and EVNO increased linearly with inhaled NO concentration. It i s reasonable to assume that a share of the quantity of inspired NO ove r time (InspVNO) because of air contamination by pollution is rejected by the ventilatory pathway. Insofar as InspVNO does not affect endoge nous production or the metabolic fate of NO in the airway, this share may be estimated as being approximately one third of InspVNO, the rema inder being taken by the endogenous pathway. Thus, air contamination b y the NO resulting from pollution greatly increases the NO response in exhaled air.