Date of Award

January 2020

Document Type


Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

Jodi Sherman


Objective: This study explores trends in procurement for 3 hospitals in Connecticut over a four-year period to better understand how much N2O is released. N2O use and frequency of conversion to epidural after N2O, as well as emergency cesarean section after N2O use is also examined. A plan for N2O destruction technology testing is outlined.

Background: Nitrous Oxide (N2O) is a well-documented greenhouse gas (GHG) and ozone-depleting agent. N2O use continues to be unregulated, and concurrently it has also become more widely adopted for use in labor and delivery in the US, though it has been popular in Europe and the UK since the 1930’s. A shift in attitudes around labor and birth has resulted in a stronger desire to avoid “medicalization” of the process; nurse midwives and other healthcare providers that are qualified to administer N2O can do so and prevent anesthesiologist intervention. The use of N2O to replace epidural is sometimes mischaracterized as a “natural” pain management strategy. As a potent GHG that is gaining popularity, it is important that use is more actively monitored and regulated by hospitals, as well as adopting technologies to prevent untreated release of N2O into the atmosphere.

Methods: N2O procurement data was analyzed over a four-year period. Conversion to CO2 equivalents was made using the global warming potential multiplier established by the Intergovernmental Panel on Climate Change (IPCC). Five hospitals were analyzed for N2O Conversion (or “failure”) over one calendar year (2019). This data was also used to assess whether parturients were at higher risk of emergency cesarean section after N2O use.

Results: N2O use in 3 hospitals within the Yale New Haven Health System (YNHHS), has increased by 99.3% over a four-year period, and is likely to continue increasing, if the patients and providers continue to prefer its use over epidurals. 42% of parturients (n=784) receiving N2O during labor went on to also receive neuraxial pain management. 3% of patients receiving N2O during a labor attempt went on to require emergency cesarean section. N2O use for pain management is associated with no increased relative risk of emergency cesarean section (RR=0.99). However, conversion from N2O to neuraxial pain management is associated with a 4.5-fold increased risk for emergency cesarean section.

Conclusions: Higher selectivity for N2O use could reduce overall GHG emissions, without sacrificing patient outcomes. US hospitals could decrease their N2O emissions by installing N2O destruction units. A sample test outline for independent verification of N2O destruction technology is outlined in this study, both in a trial and hospital setting.


This thesis is restricted to Yale network users only. It will be made publicly available on 05/27/2021