Prevention is the best way to avoid a sinus squeeze or block. Never dive when you have a cold or sinus congestion. Also, do not dive if you must use medication to open your sinuses or clear your ears. Decongestant Drugs You might think that the answer to preventing a squeeze is to take medication before you dive. Many sprays and tablets are available to relieve congestion. But none of these drugs are designed or tested to perform under water. The effects of any drug might be modified under pressure, and little is known about the potential problems that can occur when medications are used under water. A drug that causes drowsiness on the surface can be worse under water. For this reason, you should consult a doctor who knows about diving before you use any medication during a dive – even any regular medication you might be taking. Also, avoid taking any medication that you know produces side effects when you use it. Stomach and Intestines Any gas that forms in your stomach or intestines during your dive will expand during ascent. This can cause discomfort by creating pressure. To prevent this situation, avoid eating gas-producing foods before you dive. If you have problems from stomach or intestinal Chapter 4- Diving Science gas while ascending, stop or slow your ascent until the gas works its way out of your system. Teeth If you have an imperfect filling in one of your teeth, air can get under the filling. When you descend, the air in the space can compress and cause pain in your tooth. If you continue to dive, compressed air can fill the space in the tooth and loosen the filling or fracture the tooth on ascent. There is nothing you can do to equalize air pressure in a tooth. You must ascend back to the surface and have your tooth examined by a dentist. Mask Space Although it might seem obvious, divers often forget that their mask creates an air space attached to their body. This air space is also affected by pressure. As the water pressure increases during your descent, the mask is pushed against your face and the air inside the mask compresses. Because the mask is rigid, it compresses only slightly. If you do not add air to your mask, the low air pressure inside the mask will cause your mask to suck tightly on your face. The soft tissue of your face will squeeze into the mask, causing tissue damage. This type of injury is known as a mask squeeze. Bloodshot eyes can result. You should never have this type of injury because you can easily equalize the pressure inside your mask. Simply exhale a small amount of air through your nose into the mask every time you feel pressure pulling on your face and eyes. Dry Suit If you wear a dry suit, you have an air space surrounding your body. As you descend, the air inside the dry suit will compress. To keep the suit from squeezing, simply add air to the suit using the power-inflator valve. If you are wearing a dry suit during your training, your instructor will give you specific instructions in the use of your dry suit. Diving Science 111 Congested sinus under pressure Effect of ascent FIGURE 4-26. IF SWELLING OR MUCUS CLOSES A SINUS WHILE DIVING, PRESSURE WILL DEVELOP INSIDE THE SINUS DURING ASCENT.
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