Question

Explain why scuba divers should never hold their breath when they ascend to the surface.

Short answer

Scuba divers must not hold their breath while ascending because the reduction in external pressure leads to air expansion in the lungs, which can cause lung injury or barotrauma if the expanding air cannot escape.

Step-by-step solution

Understanding Boyle's Law

Understand that Boyle's Law describes the relationship between the pressure and volume of a gas at constant temperature. It states that volume of a gas is inversely proportional to its pressure. As a scuba diver ascends and the external pressure decreases, the volume of air in their lungs would expand.

Recognizing the Danger of Air Expansion

During ascent, the pressure exerted by the water decreases. If a diver holds their breath, the air inside the lungs expands due to decreasing pressure but cannot escape, which could lead to lung over-expansion, resulting in serious injury, or in extreme cases, a lung barotrauma.

Avoiding Lung Over-expansion

To prevent lung over-expansion, divers are taught to breathe continuously while ascending, as this allows the expanding air to be exhaled and thus avoiding the risk of lung injury related to pressure changes.

Key concepts

Pressure-Volume Relationship

The universe follows certain rules, one of which being Boyle's Law—a pillar of physics and chemistry that states a strict relationship between the pressure and volume of a gas. At a constant temperature, the volume of a gas is inversely proportional to the pressure it's under. This means if pressure increases, volume decreases, and vice versa.

This law is particularly relevant to scuba divers. Imagine your lungs as flexible balloons filled with air. As you dive deeper, water pressure builds up outside your body, squeezing the air in your lungs and reducing its volume. On the flip side, when you ascend, pressure drops, allowing the gas to expand. If divers don't manage this expansion by exhaling, they could face serious risks due to lung over-expansion.

Lung Over-expansion

Submerged in the depths, divers must be vigilant as the laws of physics are unforgiving. Lung over-expansion occurs when the air inside a diver's lungs expands more than the lungs can handle, similar to overinflating a balloon. The danger kicks in when ascending without exhaling—the air inside needs to go somewhere. Without a way out, the expanding air can cause the lung tissue to stretch and tear.

This not only causes immense pain but may also lead to air bubbles entering the bloodstream or air escaping to the chest cavity. In severest terms, this condition is known as a pulmonary barotrauma. Recognizing the signs of this distress and responding appropriately can be life-saving.

Lung Barotrauma

Decompression sickness may be the scuba threat most have heard of, but lung barotrauma holds its own fearsome stake. Lung barotrauma refers to the injuries one can sustain from the rapid or excessive expansion of air in the lungs. This could range from chest pain and breathing difficulties to more severe conditions like a pneumothorax, where air escapes into the space around the lungs, or arterial gas embolism, a medical emergency caused by air bubbles in the blood vessels.

These conditions are particularly dangerous because they might not only end a diving career but also be life-threatening. Education, awareness, and adherence to proper diving protocols are crucial for prevention.

Breathing Techniques for Divers

Breathing may seem instinctive, but under the sea, it becomes a skill to master. Divers use specific techniques to maintain pressure equilibrium and prevent dangers like lung over-expansion and barotrauma. The golden rule? Never hold your breath. Continuously breathing in a relaxed and controlled manner lets air exchange freely, adjusting to the changing pressures during descent and ascent.

Effective techniques include breathing slowly and deeply, avoiding rapid, shallow breathing, and making sure to exhale fully before ascending. These practices not only reduce the risk of lung injuries but can also optimize air consumption, allowing divers to extend their underwater adventure safely.