CO₂ Detection in Closed-Circuit Oxygen Divers With and Without a Distracting Task

Authors: Eynan, Mirit; Tal, Dror; Arie, Efrat; Ne'eman, Frida; Adir, Yochai

Source: Aviation, Space, and Environmental Medicine, Volume 77, Number 10, October 2006 , pp. 1028-1033(6)

Publisher: Aerospace Medical Association

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Abstract:

Eynan M, Tal D, Arie E, Ne'eman F, Adir Y. CO₂ detection in closed-circuit oxygen divers with and without a distracting task. Aviat Space Environ Med 2006; 77:1028-1033.

Introduction: Elevated arterial PCO₂ (hypercapnia) increases the risk of CNS oxygen toxicity when diving with enriched oxygen gas mixtures. A CO₂ detection and retention test is conducted as a matter of routine at the Israel Naval Medical Institute for physiological training, and as a screening tool for divers who may be prone to suffer from CNS oxygen toxicity. This test does not include an “attention distracter,” which would provide a better simulation of the true situation during actual diving. The purpose of the present study was to examine the hypothesis that the addition of cognitive tasks to the CO₂ detection and retention test might alter divers' detection ability. Methods: We assessed ventilatory and perceptual responses to variations in inspired CO₂ (range 0-5.6 kPa, 0-42 mmHg) during moderate exercise, with and without the addition of cognitive tasks, in 15 Israel Navy combat divers on active duty. The first stage was the CO₂ detection training session, followed by the CO₂ detection test session (TEST) and the CO₂ detection test session while doing cognitive tasks (COGN). The latter two sessions were performed by some of the subjects in reverse order. Results: We found that the mean (± SD) PICO₂ at the detection threshold was significantly lower in the COGN (1.7 ± 0.8 kPa, 12.7 ± 6.0 mmHg) than in the TEST (2.4 ± 0.6 kPa, 18.1 ± 4.5 mmHg). The mean PETCO₂ while inspiring 5.6 kPa (42 mmHg) CO₂ was not significantly different in the two tests. Conclusion: We suggest that the ability to detect CO₂ during a dive is not impaired, but rather improves when the diver's attention is focused on other tasks.

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Keywords: diving; CO2 detection; CO2 retention; CNS oxygen toxicity; cognitive tasks

Document Type: Research article

Publication date: 2006-10-01

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The peer-reviewed monthly journal, Aviation, Space, and Environmental Medicine (ASEM) provides contact with physicians, life scientists, bioengineers, and medical specialists working in both basic medical research and in its clinical applications. It is the most used and cited journal in its field. ASEM is distributed to more than 80 nations.
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