Is V̇O₂ suppressed during nonapnoeic facial submersion?

Area of Science:

• Physiology
• Human Physiology
• Environmental Physiology

Background:

• The mammalian dive response (DR) is characterized by oxygen conservation mechanisms.
• Key components of the DR include bradycardia, peripheral vasoconstriction, and reduced ventilation.
• The specific contribution of nonapnoeic facial submersions (NAFS) to oxygen conservation requires further elucidation.

Purpose of the Study:

• To investigate the impact of nonapnoeic facial submersions (NAFS) on oxygen consumption (V̇O₂) in humans.
• To examine the effects of varying water temperatures on physiological responses during NAFS.
• To determine if NAFS alone contributes to the oxygen-conserving effects of the DR.

Main Methods:

• 19 participants underwent simulated diving with four 2-minute NAFS.
• Submersions were conducted in both 5°C and 25°C water.
• Heart rate (HR), oxygen consumption (V̇O₂), and ventilation (V̇_E) were measured using metabolic cart and chest strap monitors.

Main Results:

• During NAFS, HR and V̇_E decreased significantly compared to baseline, indicating oxygen conservation.
• Oxygen consumption (V̇O₂) was lower during NAFS compared to baseline.
• Colder water (5°C) elicited a greater cold shock response and higher V̇_E compared to warmer water (25°C).

Conclusions:

• Nonapnoeic facial submersions alone are sufficient to induce significant oxygen conservation.
• The findings highlight the role of NAFS as a key component of the human dive response.
• Water temperature influences the physiological responses during NAFS, affecting HR and V̇_E.