Hemodynamic adjustments during breath-holding in trained divers

Area of Science:

• Human Physiology
• Cardiovascular Research
• Diving Medicine

Background:

• Voluntary breath-holding (BH) induces significant hemodynamic alterations.
• Limited data exists on maximal static immersed-body BH compared to dry conditions.
• The diving reflex's role in oxygen conservation during immersed BH is not fully understood.

Purpose of the Study:

• To investigate hemodynamic changes during maximal static immersed-body BH.
• To compare these changes with those observed during maximal dry-body BH.
• To test the hypothesis that body immersion strengthens the diving reflex, leading to better oxygen sparing and longer BH duration.

Main Methods:

• Eleven trained breath-hold divers (BHDs) participated in the study.
• Maximal dry-body BH and maximal immersed-body BH were performed.
• Hemodynamic variables including cardiac output (CO), stroke volume (SV), and heart rate (HR) were measured using bio-impedancemetry.
• Arterial oxygen saturation (SaO2) was monitored using a finger probe oximeter.

Main Results:

• Both dry and immersed BH exhibited biphasic CO and triphasic SV/HR kinetics.
• The initial phase of immersed BH showed greater reductions in CO, SV, and HR compared to dry BH.
• A later phase in immersed BH demonstrated increased SV and a further HR decrease, stabilizing CO.

Conclusions:

• Cardiodynamic variable patterns during maximal static BH are similar in dry and immersed conditions.
• The observed hemodynamic phenomena are more pronounced during immersed-body BH.
• Body immersion appears to intensify the physiological responses associated with breath-holding.