Apnoeic heart rate responses in humans. A review

Area of Science:

• Physiology
• Human Cardiovascular Response

Background:

• Research on human heart rate response to apnoea and aquatic immersion yields conflicting results.
• The existence and characteristics of apnoeic bradycardia, a potential component of the mammalian dive reflex, remain debated in humans.

Purpose of the Study:

• To review and analyze the equivocal findings regarding human heart rate responses during apnoea and apnoeic immersion.
• To identify factors contributing to discrepancies in research on apnoeic bradycardia.

Main Methods:

• Review of existing research on human physiological responses to apnoea and water immersion.
• Analysis of conflicting evidence concerning apnoeic bradycardia at rest and during exercise.

Main Results:

• A bradycardial response to resting apnoea is generally accepted, but responses during exercise are inconsistent.
• Discrepancies are attributed to varied research protocols, lack of controlled variables, and inconsistent result interpretation.
• Factors like water temperature, physical condition, lung volume, immersion depth, body position, psychological state, sex, and age influence apnoeic heart rates, with conflicting evidence for each.

Conclusions:

• Significant controversy surrounds human apnoeic heart rate responses, particularly during exercise.
• A lack of standardized research methods and inconsistent interpretation of results contribute to the existing discrepancies.
• Further research employing an integrative approach is necessary to comprehensively understand apnoeic heart rate responses and their modulators.