CO2 detection in closed-circuit oxygen divers with and without a distracting task

Area of Science:

• Marine Biology
• Physiology
• Diving Medicine

Background:

• Elevated arterial PCO2 (hypercapnia) increases the risk of CNS oxygen toxicity during dives with enriched oxygen gas mixtures.
• Routine CO2 detection and retention tests screen divers for susceptibility to CNS oxygen toxicity.
• Current tests lack cognitive challenges, unlike real diving scenarios.

Purpose of the Study:

• To investigate if adding cognitive tasks to the CO2 detection test alters divers' ability to detect hypercapnia.
• To simulate more realistic diving conditions by incorporating attention-demanding tasks.

Main Methods:

• Ventilatory and perceptual responses to inspired CO2 variations (0-5.6 kPa) were assessed in 15 Israel Navy combat divers.
• Subjects underwent a CO2 detection test with and without concurrent cognitive tasks.
• The order of the test sessions was counterbalanced for some participants.

Main Results:

• The mean partial pressure of inspired CO2 (PICO2) at the detection threshold was significantly lower during the cognitive task session (COGN) (1.7 kPa) compared to the standard test (TEST) (2.4 kPa).
• No significant difference was observed in the mean end-tidal CO2 (PETCO2) at 5.6 kPa CO2 inspiration between the two conditions.

Conclusions:

• The ability to detect CO2 during diving may improve when divers' attention is engaged by cognitive tasks.
• This suggests that cognitive load does not impair, but potentially enhances, CO2 detection in divers.