Workplace NO and NO2 during combined treatment of infants with nasal CPAP and NO

Objective To determine the workplace concentrations of NO and NO₂ in and around a paediatric incubator during inhaled NO (iNO) treatment and during an accidental emptying of NO cylinders into room air.Design We simulated iNO–nasal CPAP treatment in order to assess the impact on the occupational environment. Furthermore, two full NO cylinders for therapy, 1,000 ppm, 20 litres, 150 bar and 400 ppm, 10 litres, 150 bar, were emptied as rapidly as possible into an intensive care unit (ICU) room.Setting University hospital ICU.Measurements and results To correctly gauge the contribution from iNO–CPAP we constructed a system measuring breathing zone and room ventilation inlet-outlet values during a 10-ppm iNO treatment of a simulated infant. Maximal breathing zone values were 17.9 ± 7.0 (mean ± 95% CI) ppb for NO and 25.2 ± 4.8 ppb for NO_2. If room inlet values were subtracted, the contributions to breathing zone values emanating from iNO–CPAP were 14.8 ± 4.6 ppb for NO and 14.6 ± 4.6 ppb for NO₂. At the ventilation outlet the maximal contributions were 4.2 ± 2.9 ppb NO and 9.6 ± 4.3 ppb NO₂. During rapid total release of a gas cylinder in the ICU room, simulating an accident, we found transient NO levels comparable to the high therapeutic dosing range, but only low NO₂ levels.Conclusions Neither 8-h time-weighted average (TWA) nor 15 min short-term exposure limits (STEL) were exceeded during normal operation or during a simulated accident. The contribution of nitrogen oxides from treatment to workplace air were minor compared to those from ambient air.