title: Nitrous oxide concentration during cryotherapy.
abstract: OBJECTIVE
  The purpose of this study was to record room air concentrations of nitrous oxide during sessions of cryotherapy and to compare them with available norms. Complementary objectives were to determine the knowledge of Canadian colposcopists and to evaluate the need for education regarding nitrous oxide toxicities.
  
  
  METHODS
  Air concentrations of nitrous oxide during cryotherapy sessions were measured with an infrared gas analyzer. A survey was sent to colposcopists throughout Canada to evaluate their knowledge of toxicities of nitrous oxide.
  
  
  RESULTS
  The mean air concentrations of nitrous oxide measured were 169, 91, 99, and 103 ppm, respectively. Adding a tube to the cryotherapy scavenging outlet to dispose of the gas diminished the concentration to 17 ppm. The survey showed that 74% of the gynecologists surveyed use nitrous oxide as a refrigerant and only 18% know about the toxicities of nitrous oxide.
  
  
  CONCLUSIONS
  Without a device to dispose of nitrous oxide securely during cryotherapy, the air concentration exceeds safe levels. Education of clinicians on the toxicities of nitrous oxide should be a goal in the future.
authors.affiliation: *Gynecologic-Oncology Department and †Biomedical and Physics Engineering Service, Centre Hospitalier de l'Université de Montréal, Notre-Dame Hospital, Montréal, Québec, Canada.
authors.forename: M C
authors.initials: MC
authors.lastname: Renaud
authors.forename: P
authors.initials: P
authors.lastname: Gauthier
authors.forename: L
authors.initials: L
authors.lastname: Dubé