Table 4Key Question 4—Applicability

DomainDescription of Applicability of Evidence Compared With Question
PopulationThe study populations were healthy women in labor who should be similar to the target population. The eligibility criteria and participant characteristics were not always explicitly detailed. Some participants were excluded due to choice of alternate pain management methods.
InterventionMost studies used a 50/50 mix of nitrous and oxygen, often premixed in the form of Entonox. The 50/50 mix is available, although Entonox is not used in the U.S, and not currently approved by the FDA. The intervention varied significantly in terms of dose, frequency, and duration. In many studies participants received unspecified amounts of narcotics and/or sedating agents. Studies prior to 1980 are not applicable to current guidelines for clinical use.
ComparatorsThe comparators include standard pain management methods, such as epidural, narcotics, and nonpharmacologic methods such as TENS. However, some comparators are not commonly used and/or available for laboring women in the U.S., such as other inhalational anesthetic gases.
OutcomesThe most frequent outcomes were assessments of nausea, vomiting, dizziness, drowsiness, hypoxia, oxygen saturation, Apgar scores, and cord blood gases. Apoptosis was not addressed because there are no human studies.
SettingOnly six of 48 studies were conducted in the U.S. The standards of care are not comparable because nitrous is widely available outside of the U.S.

From: Appendix D, Applicability and Quality Tables

Cover of Nitrous Oxide for the Management of Labor Pain
Nitrous Oxide for the Management of Labor Pain [Internet].
Comparative Effectiveness Reviews, No. 67.
Likis FE, Andrews JC, Collins MR, et al.

PubMed Health. A service of the National Library of Medicine, National Institutes of Health.