Occupational exposure to nitrous oxide during procedural pain control in children: a comparison of different inhalation techniques and scavenging systems

Background: Nitrous oxide (N2O 50% in oxygen) is commonly used for painful procedures in children. Potential negative health effects associated with chronic workplace exposure limit its use. Safe occupational N2O exposure concentrations are below 25 ppm environmental concentration as a time-weighted average (TWA) and below 200 ppm as a short-time exposure level (STEL) of 15 min. Aim: The aim was to assess occupational exposure of staff during nitrous oxide administration to children using different inhalation delivery devices and scavenging systems. Methods: Staff nitrous oxide exposure during use of a double face mask (DFM) with or without a demand valve (DV) was compared with a conventional single face mask (FM). We also compared exposure using the hospital central scavenging system with a portable evacuation system. N2O concentrations, representing exposure values, were monitored within proximity to staff. Urine N2O concentration was measured in staff administering the N2O at the end of the procedural session. Results: The mean and median values of TWA and STEL within the working area were lower than recommended values in the DFM (10.8, 11.6 ppm for TWA; 13.9, 11.0 ppm for STEL) and DFM-DV groups (2.3, 2.8 ppm for TWA; 4.4, 3.5 ppm for STEL) using the portable evacuation system. The N2O urine exposure in DFM-DV group was lower than DFM group: a mean difference of 9.56 ppm (95% CI 2.65-16.46). Staff N2O urinary concentrations were within safe biological limits in both the DFM and DFM-DV groups. High exposure concentrations to N2O were recorded in all FM and FM-DV environmental and biological samples. Conclusions: The DFM system, with or without a DV, connected to a portable evacuation system during N2O administration to children for painful procedures kept N2O levels within the local environment below recommended limits.