Diving Physiology and Hazards (Wk 5)

Breath-hold diving cultures

Bajau in Southeast Asia and Ama pearl divers in Japan and Korea.

Boyle's law in diving

At constant temperature, pressure multiplied by volume is constant; doubling pressure halves lung volume.

What drives the urge to breathe?

Rising arterial carbon dioxide levels, detected by carotid bodies and aortic arch.

O₂-Hb curve right shift causes

Increased carbon dioxide, decreased pH, and increased temperature.

Risk of hyperventilation before diving

Lowers PCO₂ to delay breathing urge while oxygen keeps falling, causing blackout.

Snorkel depth limit cause

Weak inspiratory muscles cannot overcome water pressure and hose dead space.

Bradycardia in the diving reflex

Face immersion triggers the trigeminal nerve and vagus nerve to decrease heart rate.

Peripheral vasoconstriction during diving

Maintains blood pressure by increasing total peripheral resistance.

Splenic contraction function during diving

Releases stored red blood cells into the circulation.

Henry's law in SCUBA diving

Dissolved gas depends on pressure gradient and solubility; high pressure dissolves gas.

Oxygen poisoning symptom

High dissolved oxygen causes cerebral vasoconstriction, blindness, and seizures.

Cause of pneumothorax during diving

Ascending too fast with a breath held, causing lung over-expansion.

Lung squeeze occurrence

Descending until total lung capacity is below residual volume, bursting capillaries.

Decompression sickness ("the bends") cause

Nitrogen dissolved at depth forms bubbles on fast ascent, causing joint pain.

Nitrogen narcosis prevention

Use helium-oxygen mixes instead of air to avoid the anaesthetic effect.

Mask squeeze cause

Descending quickly without equalizing the mask, creating a suction effect.