Arterial oxygen desaturation kinetics during apnea

Area of Science:

• Physiology
• Human Performance
• Environmental Medicine

Background:

• Freediving involves breath-hold diving, requiring physiological adaptations to manage oxygen levels.
• Understanding oxygen desaturation rates is crucial for assessing freediver safety and performance.
• Previous studies have explored physiological responses to breath-holding, but precise quantification of desaturation rates in trained freedivers is ongoing.

Purpose of the Study:

• To quantify the rate of arterial oxygen desaturation during apnea in freedivers.
• To compare oxygen desaturation dynamics between trained freedivers and untrained controls.
• To identify physiological factors influencing the rate of oxygen desaturation during breath-hold diving.

Main Methods:

• Ten trained freedivers and ten untrained controls performed maximal face immersion apneas in cold water.
• Continuous monitoring of electrocardiogram (ECG), blood pressure, and pulse oximetry.
• Measurement of peripheral blood flow and collection of venous blood for hematocrit, lactate, and hemoglobin analysis.

Main Results:

• Freedivers achieved significantly longer apnea durations than controls.
• Freedivers exhibited greater reductions in heart rate and mean arterial pressure during apnea.
• While a sigmoid model showed no difference in desaturation rate, a two-slope continuous model indicated freedivers slowed desaturation by 2-3 times, explained by bradycardia and oxygen stores.

Conclusions:

• The sigmoidal function is insufficient for quantifying differences in oxygen desaturation rates during apnea.
• A two-slope continuous model effectively demonstrates that freedivers modulate their rate of oxygen desaturation.
• Physiological factors like larger oxygen stores and pronounced bradycardia contribute to slower arterial oxygen desaturation in freedivers.