Simulated use of premixed 0.25% isoflurane in 50% nitrous oxide and 50% oxygen

J A Ross, M E Tunstall

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Background. Isoflurane (0.25%) in premixed nitrous oxide and oxygen, 50/50, v/v (IN2O), has been suggested for pain relief in labour. Possible phase separation of the mixture was studied during simulated administration.

Methods. A sinusoidal pump set at stroke volume of 2 litres and a rate of 20-22 bpm and cycling for 1 min in three was used to simulate breathing during the painful contractions of labour.

Results. The temperature inside a 10-litre capacity cylinder did not drecrease sufficiently to cause separation of the gas mixture. Temperature in the demand valve decreased to -15.5degreesC and this caused a small amount of liquid formation within the valve. Accordingly, the inspired concentration during the first breath of mixture in a cycle could be transiently as high as 0.55%. The concentration observed at the patient connection after the first breath varied between 0.17 and 0.28%.

Conclusions. The system delivered a clinically acceptable performance although further development to avoid liquid condensation is needed.

Original languageEnglish
Pages (from-to)820-824
Number of pages5
JournalBritish Journal of Anaesthesia
Volume89
Issue number6
DOIs
Publication statusPublished - 2002

Keywords

  • Anesthesiology
  • Anesthetics, Combined
  • Cold Temperature
  • Humans
  • Isoflurane
  • Nitrous Oxide
  • Oxygen
  • labor

Cite this

Simulated use of premixed 0.25% isoflurane in 50% nitrous oxide and 50% oxygen. / Ross, J A; Tunstall, M E.

In: British Journal of Anaesthesia, Vol. 89, No. 6, 2002, p. 820-824.

Research output: Contribution to journalArticle

@article{54a003c3f8be42b4a56dec958570cd8c,
title = "Simulated use of premixed 0.25{\%} isoflurane in 50{\%} nitrous oxide and 50{\%} oxygen",
abstract = "Background. Isoflurane (0.25{\%}) in premixed nitrous oxide and oxygen, 50/50, v/v (IN2O), has been suggested for pain relief in labour. Possible phase separation of the mixture was studied during simulated administration.Methods. A sinusoidal pump set at stroke volume of 2 litres and a rate of 20-22 bpm and cycling for 1 min in three was used to simulate breathing during the painful contractions of labour.Results. The temperature inside a 10-litre capacity cylinder did not drecrease sufficiently to cause separation of the gas mixture. Temperature in the demand valve decreased to -15.5degreesC and this caused a small amount of liquid formation within the valve. Accordingly, the inspired concentration during the first breath of mixture in a cycle could be transiently as high as 0.55{\%}. The concentration observed at the patient connection after the first breath varied between 0.17 and 0.28{\%}.Conclusions. The system delivered a clinically acceptable performance although further development to avoid liquid condensation is needed.",
keywords = "Anesthesiology, Anesthetics, Combined, Cold Temperature, Humans, Isoflurane, Nitrous Oxide, Oxygen, labor",
author = "Ross, {J A} and Tunstall, {M E}",
year = "2002",
doi = "10.1093/bja/aef279",
language = "English",
volume = "89",
pages = "820--824",
journal = "British Journal of Anaesthesia",
issn = "0007-0912",
publisher = "ELSEVIER APPL SCI PUBL LTD",
number = "6",

}

TY - JOUR

T1 - Simulated use of premixed 0.25% isoflurane in 50% nitrous oxide and 50% oxygen

AU - Ross, J A

AU - Tunstall, M E

PY - 2002

Y1 - 2002

N2 - Background. Isoflurane (0.25%) in premixed nitrous oxide and oxygen, 50/50, v/v (IN2O), has been suggested for pain relief in labour. Possible phase separation of the mixture was studied during simulated administration.Methods. A sinusoidal pump set at stroke volume of 2 litres and a rate of 20-22 bpm and cycling for 1 min in three was used to simulate breathing during the painful contractions of labour.Results. The temperature inside a 10-litre capacity cylinder did not drecrease sufficiently to cause separation of the gas mixture. Temperature in the demand valve decreased to -15.5degreesC and this caused a small amount of liquid formation within the valve. Accordingly, the inspired concentration during the first breath of mixture in a cycle could be transiently as high as 0.55%. The concentration observed at the patient connection after the first breath varied between 0.17 and 0.28%.Conclusions. The system delivered a clinically acceptable performance although further development to avoid liquid condensation is needed.

AB - Background. Isoflurane (0.25%) in premixed nitrous oxide and oxygen, 50/50, v/v (IN2O), has been suggested for pain relief in labour. Possible phase separation of the mixture was studied during simulated administration.Methods. A sinusoidal pump set at stroke volume of 2 litres and a rate of 20-22 bpm and cycling for 1 min in three was used to simulate breathing during the painful contractions of labour.Results. The temperature inside a 10-litre capacity cylinder did not drecrease sufficiently to cause separation of the gas mixture. Temperature in the demand valve decreased to -15.5degreesC and this caused a small amount of liquid formation within the valve. Accordingly, the inspired concentration during the first breath of mixture in a cycle could be transiently as high as 0.55%. The concentration observed at the patient connection after the first breath varied between 0.17 and 0.28%.Conclusions. The system delivered a clinically acceptable performance although further development to avoid liquid condensation is needed.

KW - Anesthesiology

KW - Anesthetics, Combined

KW - Cold Temperature

KW - Humans

KW - Isoflurane

KW - Nitrous Oxide

KW - Oxygen

KW - labor

U2 - 10.1093/bja/aef279

DO - 10.1093/bja/aef279

M3 - Article

C2 - 12453923

VL - 89

SP - 820

EP - 824

JO - British Journal of Anaesthesia

JF - British Journal of Anaesthesia

SN - 0007-0912

IS - 6

ER -