Training improves divers' ability to detect increased CO2

Mirit Eynan, Yochanan I. Daskalovic, Yehuda Arieli, Ran Arieli, Avi Shupak, Esther Eilender, Dan H. Kerem

Research output: Contribution to journalArticlepeer-review


Background: Elevated arterial PCO2 (hypercapnia) is a known risk in diving with closed circuit breathing apparatus. In a retrospective study, we determined CO2 retention and the ability to detect CO2 in novice divers who were either CO2-recognition-trained subjects (TS) or untrained subjects (UTS). Methods: Ventilatory and perceptual responses to variations in inspired CO2 (range 0-5.6 kPa, 0-42 mm Hg) during moderate exercise were assessed in novice Israeli Navy divers on active duty. Tests were carried out on 231 TS and 213 UTS. Results: The minimal mean inspired PCO2 that could be detected was 4.8 ± 1.6 kPa (36 ± 12 mm Hg) in UTS and 2.9 ± 0.7 kPa (22 ± 5 mm Hg) in TS (p < 0.0001). No significant changes were found in PETCO2 between the two groups during exposure to a PICO2 of 5.6 kPa (42 mm Hg). There were 46 TS who were found to be CO2 retainers (more than +1 SD above the mean) and 19 were classified as poor detectors (more than +1 SD above the mean). Seven subjects exhibited both traits. During actual oxygen diving performed later by this group, the only four cases of CNS-oxygen toxicity were among those seven subjects (p < 0.01). Conclusions: We conclude that CO2 recognition training improves the diver's capability to detect CO2. We suggest that a diver who is both a poor CO2 detector and a CO2 retainer will be prone to CNS-oxygen toxicity.

Original languageEnglish
Pages (from-to)537-545
Number of pages9
JournalAviation Space and Environmental Medicine
Issue number5 I
StatePublished - 1 May 2003


  • CO detection
  • CO retention
  • Hyperbaric oxygen
  • Hypercapnia

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health


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