Physiology of underwater diving

The study of physiological effects on the human body during underwater diving

Introduction

The physiology of underwater diving involves the study of how the human body responds to the unique conditions encountered while diving beneath the surface of the water. These conditions include increased pressure, changes in breathing gas composition, and the effects of immersion in water. Understanding these physiological responses is crucial for ensuring the safety and health of divers.

Pressure and Depth

A scuba diver experiences increased pressure with depth.

As a diver descends, the pressure exerted by the water increases. This is due to the weight of the water above the diver, which increases by approximately 1 atmosphere (atm) for every 10 meters (33 feet) of depth. This increase in pressure affects the body in several ways:

• Compression of Air Spaces: Air-filled spaces in the body, such as the lungs, sinuses, and middle ear, are compressed under increased pressure. Divers must equalize these spaces to prevent discomfort or injury, a process known as "ear clearing" or "equalizing."
• Boyle's Law: According to Boyle's Law, the volume of a gas is inversely proportional to the pressure exerted on it. This means that as pressure increases, the volume of air in the lungs decreases, which can affect buoyancy and breathing.

Breathing Gas Composition

Divers typically breathe compressed air, which is a mixture of approximately 21% oxygen and 79% nitrogen. However, at greater depths, the partial pressures of these gases increase, leading to potential physiological effects:

• Nitrogen Narcosis: At depths greater than 30 meters (100 feet), the increased partial pressure of nitrogen can have a narcotic effect, impairing a diver's judgment and motor skills. This condition is known as nitrogen narcosis.
• Oxygen Toxicity: Breathing oxygen at high partial pressures can lead to oxygen toxicity, which can cause seizures and other serious health issues. Divers using enriched air mixtures, such as nitrox, must be aware of the risks of oxygen toxicity.

Immersion Effects

The immersion of the body in water also has significant physiological effects:

• Hydrostatic Pressure: The pressure exerted by water on the body affects blood circulation. Immersion leads to a shift of blood from the extremities to the chest, increasing central blood volume and cardiac output.
• Thermoregulation: Water conducts heat away from the body more efficiently than air, which can lead to hypothermia if a diver is not adequately protected by a wetsuit or drysuit.

Decompression Sickness

Decompression sickness, also known as "the bends," occurs when dissolved gases, primarily nitrogen, come out of solution and form bubbles in the body as a diver ascends and pressure decreases. To prevent this, divers must ascend slowly and may need to perform decompression stops to allow gases to be safely eliminated from the body.

Related Pages

• Scuba diving
• Hyperbaric medicine
• Decompression theory
• Diving safety