Which gas law best explains diving medical problems such as ear and sinus squeeze?

• A. Boyle's law
• B. Charles's law
• C. Avogadro's law
• D. Dalton's law

Answer: (A)

When you dive, the water around you increases the ambient pressure. Gas in any closed space inside your body will respond to that changing pressure. Boyle's law states that, at a constant temperature, pressure and volume are inversely related. So as you descend and external pressure rises, the volume of gas trapped in the middle ear and in the sinuses tends to shrink. If you can’t equalize by letting air into or out of those spaces, a pressure difference builds across the eardrum or sinus walls, causing ear and sinus squeeze (barotrauma). That’s why equalizing during descent and ascent is essential.

Other gas laws don’t explain this mechanism as directly. Charles's law links temperature and volume at constant pressure, not the change in external pressure you experience while diving. Avogadro's law deals with the amount of gas and its volume at a given pressure and temperature, not how external pressure changes compress or expand trapped air. Dalton's law covers how gas mixtures behave in terms of partial pressures, which is important for breathing gases but not the pressure-induced squeezing of air spaces in the ears and sinuses.