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Assessment of Environmental Exposure to Nitrous Oxide in Labor and Delivery Rooms During Self-administered Nitrous Oxide Labor Analgesia
Abstract Number: F-45
Abstract Type: Original Research
Introduction: Nitrous Oxide (N2O) is offered as a self-administered labor analgesic via facemask with patient-initiated expiratory scavenging (1). Ambient N20 levels are dependent on proper use of the scavenging system, mask fit, and proper mask use to capture expired gases (2,3). Chronic N20 exposure can cause adverse health effects (4,5). The objective of this study was to determine whether ambient N20 levels during self-administered use were elevated above the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit (REL) of 25 parts per million (ppm) based on a time-weighted average (TWA) concentration of exposure to waste anesthetic gas (6).
Methods: To assess ambient N20 levels, passive sampling badges were obtained from Assay Tech Labs, opened at the start of N2O administration, and placed in the patient’s respiratory zone with the exposure duration recorded. In total, 48 badges were analyzed by gas chromatography to determine the average N2O concentration. Univariate statistical analysis was conducted using SAS version 9.3 to estimate the proportion of measurements exceeding the REL and characterize result variability and distribution.
Results: Statistical analyses showed appreciable variability in N2O concentrations (MN 201, SD 394 ppm), partially attributable to a few extreme values. However, a non-parametric analysis revealed a greater than 99% probability that the median value (85ppm) exceeded the NIOSH REL.
Conclusion: Initial study results indicate that labor and delivery personnel may be exposed to N2O in excess of the NIOSH REL. To further assess occupational exposure risks, we propose additional investigation with robust personal N20 exposure characterization to obtain direct exposure data for labor and delivery staff compared to hospital staff not associated with N20 use. Additionally, characterizing delivery room air exchange, patient compliance with scavenging, mass N20 removal daily, and equipment maintenance will allow for additional risk screening to identify current conditions and make recommendations to optimize safe N20 use in labor and delivery settings (7).
1 Collins, M. 2012. Nitrous Oxide for Labor Analgesia. Rev. Ob and Gyn. 5.3-4, e126-e131.
2 Henderson KA. 2003. Occupational exposure of midwives to nitrous oxide. Occup Environ Med 60:958-61.
3 Newton C. 1999. The occupational exposure of midwives to nitrous oxide – a comparison between two labour suites. Int J Obstet Anesth 8: 7-10.
4 Sweeny B. 1985. Toxicity in bone marrow in dentists exposed to nitrous oxide. BMJ 291: 567-569.
5 NIOSH. 2014. NIOSH Warns: Nitrous Oxide Continues to Threaten Health Care Workers. https://www.cdc.gov/niosh/updates/94-118.html
6 NIOSH Pocket Guide to Chemical Hazards. 2005. https://www.cdc.gov/niosh/docs/2005-149/pdfs/2005-149.pdf.
7 Pichelin, M. 2016. Modeling levels of nitrous oxide exposure for healthcare professionals during EMONO usage.