The use of inhaled nitrous oxide for flexible sigmoidoscopy: a placebo-controlled trial

Endoscopy. 2000 Jun;32(6):457-60. doi: 10.1055/s-2000-652.


Background and study aims: Flexible sigmoidoscopy is a widely used diagnostic technique which is increasingly being adopted as part of bowel cancer screening programmes. It is conventionally performed without sedation or analgesia, but significant numbers of patients experience mild to moderate discomfort during the procedure. The aim of this study was to assess the usefulness of self-administered nitrous oxide to reduce discomfort during flexible sigmoidoscopy, which may have an effect of improving compliance.

Patients and methods: In a double-blind, randomized, placebo-controlled study, 87 patients were enrolled. Of these, 45 received nitrous oxide/oxygen (50% mix) to inhale during the procedure and 42 received oxygen alone. The patients recorded their opinions on the efficacy of the agent in a questionnaire after the examination. The endoscopist recorded the success of the procedure.

Results: The groups were well matched for age and sex. Significant reductions in levels of discomfort and increased levels of agreement to undergo the procedure again were noted for the actively treated group (P < 0.05). No significant differences in side effects or success of the procedure were observed.

Conclusions: The addition of self-administered nitrous oxide offered significant benefits in the area of patient discomfort during flexible sigmoidoscopy. The availability of this agent is useful in clinical practice and may enhance compliance with a screening programme.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Anesthetics, Combined*
  • Double-Blind Method
  • Female
  • Humans
  • Male
  • Middle Aged
  • Nitrous Oxide*
  • Oxygen*
  • Patient Satisfaction
  • Sigmoidoscopy*


  • Anesthetics, Combined
  • Entonox
  • Nitrous Oxide
  • Oxygen