Cardiac function during breath-hold diving in humans: an echocardiographic study

Area of Science:

• Cardiovascular Physiology
• Human Diving Physiology

Background:

• Marine mammals exhibit reduced cardiac output during breath-hold diving.
• Human cardiovascular responses to breath-hold diving are not fully understood.
• Submersible echocardiography enables cardiac assessment during diving.

Purpose of the Study:

• To evaluate cardiovascular changes in humans during breath-hold diving using Doppler echocardiography.
• To compare human diving responses to those of marine mammals.

Main Methods:

• Doppler echocardiography was used to assess cardiac function in 10 males at 3m depth and 14 males at 10m depth.
• Measurements were taken in dry conditions and during breath-hold dives.
• Key parameters included heart rate, stroke volume, cardiac output, and diastolic flow patterns.

Main Results:

• At 3m and 10m depths, significant reductions in heart rate, stroke volume, and cardiac output were observed.
• Left atrial dimensions and deceleration time of early diastolic transmitral flow (DTE) decreased.
• Early transmitral flow velocity increased significantly at 10m depth.
• Right cardiac chamber dimensions remained unchanged.

Conclusions:

• Breath-hold diving induces cardiovascular changes in humans similar to marine mammals.
• Hemodynamic effects may be due to chest constriction and pulmonary blood shift.
• Diving-induced diastolic dysfunction patterns were noted, resembling restrictive heart disease.