End-Tidal oxygen measurement compared with patient factor assessment for determining preoxygenation time

H. A. Machlin, P. S. Myles, C. B. Berry, P. J. Butler, D. A. Story, B. J. Heath

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Time to adequate preoxygenation was assessed in 200 elective surgical patients, using measurement of end-tidal oxygen concentration. A variety of patient factors were assessed as to their ability to predict the time required to preoxygenate a patient. Of the 200 patients, 23 (11.5%) were unable to be adequately preoxygenated; most of these cases were due to a poor mask fit. The average time for preoxygenation was 154 seconds (range 43-364 seconds). Of those patients who could be preoxygenated, 46 (23%) required more than three minutes. Although a regression equation could be constructed to calculate time required for preoxygenation, the wide standard errors of the coefficients preclude a clinically useful predictive equation. We thus found that we could not accurately predict time required for preoxygenation and that a routine three minutes preoxygenation may not be sufficient for many patients. However, the measurement of end-tidal oxygen concentration is a very useful method of determining the end-point for preoxygenation.

Original languageEnglish
Pages (from-to)409-413
Number of pages5
JournalAnaesthesia and Intensive Care
Issue number4
Publication statusPublished - 1993


  • Anaesthesia
  • End-tidal
  • Measurement techniques
  • Monitoring
  • Oxygen
  • Paramagnetic
  • Preoxygenation

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