Temporal changes in pulmonary gas exchange efficiency when breath-hold diving below residual volume

Area of Science:

• Physiology
• Marine Biology
• Sports Science

Background:

• Breath-hold diving elicits extreme physiological responses to exercise, asphyxia, and hydrostatic pressure.
• Understanding cardiopulmonary adaptations during and after deep dives is crucial for diver safety and performance.

Purpose of the Study:

• To investigate the acute and short-term (2.5 hours) impacts of deep breath-hold diving on cardiopulmonary function.
• To determine the relationship between hydrostatic lung compression and pulmonary gas exchange efficiency.

Main Methods:

• Assessed cardiopulmonary function in 25 divers performing 66 deep dives (up to 117m) using non-invasive techniques.
• Measured pulmonary gas exchange (O2 deficit), ultrasound B-lines, lung compliance, and pulmonary haemodynamics.
• Quantified lung compression relative to residual volume (RV).

Main Results:

• Pulmonary gas exchange inefficiency (increased O2 deficit) correlated significantly with dive depth (r² = 0.345, P < 0.001).
• Dives causing lung compression to or below RV showed significantly higher O2 deficits post-dive.
• While lung squeeze symptoms correlated with greater deficits, cardiac output and pulmonary artery systolic pressure remained unchanged.

Conclusions:

• Deep breath-hold diving leads to transient impairments in pulmonary gas exchange efficiency.
• Hydrostatic lung compression is a key factor contributing to these post-dive gas exchange abnormalities.
• These findings offer new insights into lung and pulmonary vasculature behavior following deep diving.