163 Nitrous Oxide Exposure in Emergency Medical Services Providers: A Novel Direct Measurement Approach With Concerning Preliminary Findings

Abstract

The use of inhaled nitrous oxide (N2O) as a pain control agent by emergency medical services (EMS) has notably increased nationwide in recent years. N2O offers numerous benefits as a out-of-hospital analgesic but is also exhaled unmetabolized by patients and accumulates in confined areas, with potential for chronic health implications or acute intoxication at high levels. While there is a wealth of literature addressing occupational N2O exposure in hospital and outpatient settings, the literature on out-of-hospital provider exposure is outdated and inadequate. This ongoing study is the first to measure levels of EMS provider exposure to N2O during actual (non-simulated) patient encounters. The primary study objective is to obtain an average value of ambient N2O concentration during a typical EMS patient encounter in which N2O is used, and to compare this sample mean to national standards for safe exposure limits. Ambient N2O concentrations were directly sampled via externally validated dosimeter badges (Kem Medical Products Corp.) worn in the breathing zone of EMS providers while caring for patients who met clinical criteria for (and were subsequently given) N2O, on-scene and/or during transport, as dictated by existing statewide EMS protocols for pain control. The primary provider of participating EMS crews unsealed and donned a dosimeter badge when N2O was started and wore the badge until care was transferred at the hospital. The delivery system (Nitronox) provided N2O with oxygen in a fixed 50/50 mix; patients self-administered ad libitum via a hand-held mouthpiece, with flow regulated via a demand valve. Per state protocol, crews were always required to open a patient compartment window and utilize the exhaust fan during N2O administration. Used badges were immediately re-sealed and later shipped for lab analysis by the supplier. Additional data including total exposure time were gathered for each call. Enrollment was started on a continuous basis at three 911 agencies within a single EMS district containing both urban and rural service areas in late March 2019. At the time of abstract submission, lab analysis was complete for three dosimeters, with a fourth pending. The average ambient N2O concentration over the three corresponding patient encounters was calculated to be 275 parts per million (ppm) as a time-weighted average (TWA). This preliminary sample mean exceeds the National Institute of Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL) of 25 ppm as a TWA, as well as the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) of 50 ppm as a TWA. Of note, during the only patient encounter in which N2O was used as the exclusive pain control agent for the duration of transport, ambient concentrations exceeded the validated limit of the dosimeter (N2O >700 ppm as a TWA). Preliminary findings suggest EMS providers in the study area may be unintentionally exposed to ambient N2O concentrations in excess of the NIOSH REL and ACGIH TLV during administration for out-of-hospital analgesia; however, no conclusions may be drawn yet given the current n of 3. Data collection was ongoing at the time of submission; if further data suggests excessive exposure, it may prompt early study termination and reassessment of EMS N2O protocols or delivery systems.