Sinus squeeze, medically known as sinus barotrauma, is a common pressure-related injury experienced by divers. It occurs when the pressure inside the air-filled sinus cavities cannot equalize with the increasing ambient pressure of the surrounding water during descent. Sinus squeeze is largely preventable through proper technique and preparation. Understanding the underlying physics and anatomy is the first step toward a safe and comfortable dive.
Understanding How Sinus Squeeze Happens
The cause of sinus squeeze is directly related to Boyle’s Law, which states that pressure and volume are inversely proportional for a fixed amount of gas. As a diver descends, ambient water pressure increases, causing the volume of air in the sinuses to decrease. This pressure differential creates a vacuum effect inside the sinus cavity relative to the surrounding tissues.
The air in the sinuses normally equalizes through small openings called ostia, which connect the sinuses to the nasal passages. If the ostia are obstructed, the air inside the sinus cannot be replenished to match the external pressure, resulting in the “squeeze.” This pressure imbalance pulls on the blood vessels and mucosal lining, causing sharp pain, tissue swelling, and potentially leading to fluid accumulation or bleeding. The frontal and maxillary sinuses are the most frequently affected, often presenting as pain in the forehead or upper cheeks.
Essential Equalization Practices
The most direct way to prevent sinus squeeze is by actively introducing air into the sinuses to counteract the external pressure. This process, called equalization, should begin before any discomfort is felt, ideally within the first few feet of descent, where the pressure change is most rapid. Starting early and equalizing frequently is a safer approach than waiting for pressure to build.
The Valsalva maneuver is a common method where a diver pinches the nostrils and gently blows, forcing air from the lungs into the nasal passages. This technique is less controlled and can create excessive pressure if performed too forcefully, carrying a risk of injury.
A gentler, more controlled option is the Frenzel maneuver, which uses the tongue as a piston to push air toward the nasal cavity while the nostrils are pinched. This method does not involve the diaphragm or abdominal muscles, making it more efficient and reducing the risk of over-pressurization. Other techniques, such as swallowing or wiggling the jaw, can supplement these primary maneuvers to help open the ostia.
If resistance or pain is met during descent, stop descending and immediately ascend slightly until the discomfort is relieved. The diver should then re-equalize at that shallower depth and attempt a slower descent. Forceful or persistent equalization against resistance can compound the injury and must be avoided.
Pre-Dive Health and Medication Strategies
A diver’s health significantly influences the ability to equalize and prevent a squeeze. Congestion from a cold, allergies, or an upper respiratory tract infection causes the mucosal lining to swell, physically blocking the ostia. Diving while congested is the greatest risk factor for barotrauma, so the safest strategy is to postpone the dive until symptoms have fully resolved.
In cases of mild congestion, some divers consider using over-the-counter medications, but this requires caution. Oral decongestants like pseudoephedrine work by constricting blood vessels, temporarily shrinking swollen membranes and opening air passages. It is recommended to test these medications before diving to ensure there are no adverse side effects, such as nervousness or a rapid heartbeat, that could impair safety.
Nasal sprays, such as oxymetazoline, also reduce swelling but carry the risk of rebound congestion. If the decongestant effect wears off at depth, the nasal membranes can swell back up, creating a “reverse squeeze” on ascent as expanding air becomes trapped. A safer alternative is a nasal steroid spray, which reduces inflammation over time without the rebound effect, though it must be started days or a week before the dive to reach full effectiveness. Staying well-hydrated also helps keep mucus thin, aiding passive drainage.
Recognizing and Recovering from Sinus Barotrauma
Despite preventative efforts, sinus barotrauma can still occur, so recognizing the symptoms is important for immediate action and recovery. The primary sign is sharp facial pain, often localized above the eyes (frontal sinuses) or in the cheeks (maxillary sinuses). After surfacing, a diver may notice blood-tinged mucus in their mask or a minor nosebleed, which signals ruptured blood vessels in the sinus lining.
If pain is experienced during descent, stop descending and ascend a short distance until the pain subsides. If equalization remains impossible after a second attempt, the dive must be aborted to prevent further tissue damage.
Post-dive recovery often involves using over-the-counter pain relievers and continuing decongestants or nasal steroids to reduce swelling. Severe or persistent symptoms, such as prolonged pain, significant bleeding, or a thick, bloody discharge, require consultation with a medical professional, preferably an ENT specialist. A surface interval of several weeks may be necessary to allow the tissues to fully heal before attempting to dive again.