The increasing pressure experienced when descending underwater can compress the air spaces within the body, causing discomfort, particularly in the ears. This sensation, known as ear squeeze or middle ear barotrauma, occurs because the dense water quickly increases the pressure on the outside of the eardrum. To prevent damage, this external pressure must be balanced by increasing the air pressure inside the ear. Learning to actively equalize this pressure is a fundamental skill for anyone engaging in diving, snorkeling, or deep free-diving. Effective equalization ensures the integrity of the delicate ear structures and allows for pain-free underwater exploration.
The Biological Mechanism of Pressure Change
The ear’s middle section is an air-filled cavity separated from the outer ear canal by the eardrum. This space is connected to the back of the throat by a narrow channel called the Eustachian tube. Normally, this tube is closed, but it opens when swallowing or yawning to allow air exchange and equalize pressure.
As a person descends underwater, the surrounding water pressure increases significantly, described by Boyle’s Law. This law explains that as external pressure rises, the volume of a gas decreases proportionally. The air inside the middle ear cavity compresses, causing a relative vacuum and pulling the eardrum inward. This inward bulging stretches the eardrum’s sensory nerves, causing pressure and pain. To counteract this effect, air must be pushed from the throat through the Eustachian tube into the middle ear space to restore the original volume and balance the pressure.
Essential Techniques for Equalizing Pressure
The ability to equalize relies on consciously opening the Eustachian tubes to allow high-pressure air from the throat to enter the middle ear. A core principle is to equalize early and frequently, ideally before any pain or discomfort is felt. Divers should begin equalizing before descending and repeat the maneuver every few feet to stay ahead of the pressure changes.
The most common technique is the Valsalva maneuver, which involves pinching the nostrils closed and gently blowing air through the nose. This action forces air into the Eustachian tubes due to pressure buildup in the throat. However, this method does not use the muscles that naturally open the tubes and can be too forceful, potentially causing injury if performed aggressively.
A gentler and often more effective method is the Toynbee maneuver, where a person pinches their nose and swallows. Swallowing pulls open the Eustachian tubes, and the closed nose compresses air against the openings, allowing air to pass more naturally. Another technique is the Frenzel maneuver, favored by many experienced divers because it is less reliant on lung power. With the nose pinched, the diver closes the back of the throat and uses the tongue as a piston to compress air and force it into the tubes.
When Equalization Fails: Recognizing Barotrauma
Failure to equalize the pressure differential during descent can lead to middle ear barotrauma, the most common diving-related injury. The first sign is typically a feeling of fullness or discomfort, which quickly escalates to sharp, intense pain as the eardrum stretches inward. Continued descent forces fluid and blood to leak into the middle ear space, leading to a condition known as a middle ear squeeze.
The most severe consequence of barotrauma is the rupture of the eardrum, which may bring immediate pain relief but allows cold water to rush into the middle ear. This sudden temperature change can stimulate the inner ear, causing severe vertigo, disorientation, and nausea.
Another risk occurs during ascent, known as a reverse block, where expanding air in the middle ear cannot escape due to a blocked Eustachian tube. Reverse block causes the eardrum to bulge outward, leading to pain and potentially a rupture, often signaled by dizziness or vertigo. If any discomfort or pain is felt, the immediate action must be to stop descending, ascend slightly until the pressure clears, and attempt equalization again.
Pre-Dive Preparation and Safety Guidelines
Preparation before entering the water significantly reduces the risk of equalization problems. It is crucial to never dive while congested from a cold or allergies, as swollen mucous membranes can block the Eustachian tubes and prevent air passage. Practicing equalization techniques on land before a dive can help ensure the tubes are functional and ready for pressure changes.
During the descent, controlling speed is a primary safety guideline, as the most significant pressure changes occur in the first ten feet of water. Using a descent line provides a visual reference and allows for a slow, controlled drop, making it easier to equalize proactively. Descending feet-first may also be beneficial, as some research suggests this body position allows for easier opening of the Eustachian tubes. If pain persists after gentle attempts to equalize, a diver must stop the descent and ascend to a comfortable depth, never forcing the issue.