Diving Injuries

Injuries Due to Direct Effects of Pressure

Arterial Gas Embolism

When we ascend from a dive, the air in our lungs expands. This is a direct application of Boyle's Law; when pressure decreases, the volume will increase. If you do not exhale and allow the gas an escape, it will find its own path out of the lungs by bursting a hole in the overexpanded lung. This results in an injury referred to as a Pulmonary Barotrauma. The injury can range from mild, to a complete collapse of the lung. For this reason, it is very important to never hold one's breath on ascent.

The air that escapes can move into a few different areas and cause different problems depending on the site. Sometimes the air can escape into the pulmonary venous system where it will move through the heart and into the arteries. Arteries are the vessels that carry blood away from the heart to the different tissues of the body. When this occurs, bubbles form in the blood, causing Arterial Gas Embolism. These bubbles continue to expand with decreasing pressure upon ascent which can cause problems if they reach a vessel that is too small for them to move through. When this occurs, the bubbles become stuck and blood is unable to move through the vessel. If this occurs in areas that supply major organs such as the heart or brain, serious damage can occur. Unfortunately, there is no way to predict where the bubbles will end up.

There are several factors that can increase one's susceptibility to gas embolism. First, temporary obstruction of an air passage, as might occur with bronchitis or a cold, can increase one's risk. Additionally, coughing or sneezing on a ascent can also increase the risk. Hence, it is advisable to stop an ascent if one feels a cough or sneeze coming on.

Symptoms of gas embolism are dizziness, headache, or a feeling of great anxiety. Unconsciousness, shock and convulsions can quickly follow. Upon first noting the symptoms, arrangement for transfer to a recompression chamber should be made. The only true treatment of such an injury is recompression in a hyperbaric chamber. Until arrival at a recompression center, the individual should be kept in a head-down position at a 15 degree angle. This position may help keep bubbles in the circulation from reaching the brain. The administration of oxygen and fluids may also be helpful.

Pneumothorax

Air that escapes the lung during a barotrauma can also enter the space outside of the lung, called the pleural space. This area is usually airtight. When air moves from the lungs into this area, the injury is called Pneumothorax. Pneumothorax as a result of barotrauma is relatively rare; however, it can be quite serious when it occurs. One possible result is Tension Pneumothorax. This results when the hole that the air exited through acts as a one-way valve. Since the pleural space is airtight, the expansion of the air upon ascent places increasing pressure on the heart and the other lung. As the pressure on the heart increases, the heart becomes less able to function efficiently and can ultimately become unable to function at all. Additionally, pressure on the uninjured lung can cause it to collapse, causing a situation where the individual is unable to properly exchange air.

Symptoms of Pneumothorax are severe pain, reduction of breathing capability, and sometimes the coughing of blood. Treatment of such an injury usually involves a chest puncture to release the trapped air. In some cases, recompression is also necessary.

Mediastinal and Subcutaneous Emphysema

Mediastinal Emphysema and Subcutaneous Emphysema are both due to air being forced into tissues outside of the lungs. Mediastinal Emphysema is the movement of air into the tissues around the heart, the major blood vessel and the trachea. With ascent, the trapped gas expands and can cause impaired venous return. Symptoms are usually pain under the sternum and shortness of breath. Treatment for a mild case can be relatively symptomatic, while more severe cases may require oxygen therapy and/or recompression. Subcutaneous Emphysema is caused by air being forced into the tissue beneath the skin of the neck. Mild cases show symptoms of only a feeling of fullness in the neck. More severe cases can present with a crackling of the skin to the touch. Treatment is usually recommended as oxygen therapy, as the oxygen will speed absorption of the subcutaneous air.

Ear Problems

Difficulties with the ear resulting directly as a result of pressure changes while diving are common. The human ear has air-containing areas known as the external and middle ear spaces. These are what allow us to transform airborne sound energy into signals that our brain can read. When a difference in air pressures exists between these two areas, the eardrum's shape can become distorted. Under normal circumstances, the eustachian tube, which connects the middle ear to the throat, should allow equalization of pressure in the middle ear with ambient pressure. If the tube is blocked for some reason; however, injury to the eardrum and/or the middle ear can occur. In the most severe cases the eardrum and/or the round window can be ruptured. More common though, is a manifestation of the pressure difference between the two sides of the eardrum, called Barotitis media, or middle ear squeeze. This is a somewhat uncomfortable problem, but usually reversible simply by returning to a point higher in the water where pressure is reduced. Descent can then be attempted again with careful use of one of several techniques for equalizing the ear pressure. Swallowing, yawning or gently blowing against a closed mouth with the nosed pinched are all possible ways to relieve this pressure differential and the discomfort.

Injuries Due to Indirect Effects of Pressure

Decompression Sickness

Almost all divers have heard of Decompression Sickness (DCS), which refers to the illness that may occur following a reduction in pressure, such as resurfacing from depth. When we dive, nitrogen passes from our air tank with the air we are breathing, enters the lungs, and changes to the dissolved form as it passes from the lungs into the pulmonary blood vessels. This is termed ongassing. The dissolved nitrogen travels with the blood through the body to the various tissues. As we descend on a dive, the pressure is constantly increasing and increased amounts of nitrogen are being dissolved and carried throughout the body. Later, as we ascend, the nitrogen will move out of the tissues, into the blood stream and back to the lungs where it will come out of solution as it is exhaled as a gas (off gassing). At least, this is what we hope happens. If we ascend to rapidly, our bodies are unable to offgass as quickly as required, and the nitrogen can come out of solution while it is still in our blood and tissues. This causes the formation of small bubbles, made up mostly of nitrogen, but also some oxygen and carbon dioxide (Recall that air is comprised of 78% N, 21% O and less than 1% CO2). As we have already learned, bubbles like those released during a pulmonary barotrauma, can cause many different types of problems.

Unlike pulmonary barotrauma, bubbles from DCS an occur in almost any tissue in the body. When the bubbles develop they often cause compression of nearby blood vessels, lymph vessels and nerves. Compression of a blood vessel can stop flow through that vessel, leading to a lack of oxygen for the tissues that the vessel supports. Lymph vessels carry fluid, that if unable to drain, can cause expansion of the vessel and swelling. Possibly more serious than the first two, is compression of nerves. Nerves are very sensitive structures and compression can cause pain and impaired function.

In addition to having mechanical complications, bubble formation can have biochemical complications as well. Leukocytes, white blood cells, and platelets, blood clotting cells will aggregate and adhere to bubbles. This can add to existing mechanical problems of obstructed blood flow and swelling. Extreme fatigue, called inappropriate fatigue, can also result from the releasing of potent chemicals by the lungs. When the lungs become overwhelmed by the need to filter out the gas bubbles, they respond by releasing the chemicals.

DCS usually manifests after the diver has already completed his/her ascent. In some cases, it may take up to several hours following a dive for any symptoms to even occur. Because the bubbles can form in so many different places, the list of potential symptoms can be quite large. For any occurrence of unexplained symptoms following a dive, a doctor should be consulted. The best prevention for DCS is slow ascent rate, the regular use of safety stops and careful dive planning with the use of an approved dive table.

Oxygen Toxicity

Although it may seem paradoxical, oxygen in high enough concentrations, is toxic to all living things. When humans get too much oxygen, it causes Oxygen Toxicity. Humans require oxygen to survive, but we receive it in carefully prescribed amounts. First, when on land at sea level, oxygen makes up about 21 percent of the air we breath. When we descend to depths, it is still just 21 percent of the air we breath. Because of the increased pressure, we will breath larger quantities of air, thus receiving more molecules of oxygen. This is not a problem though, because our hemoglobin only releases oxygen to areas that have a low oxygen level. This way, tissues only receive the amount of oxygen they need. For this reason, oxygen toxicity is usually not a concern for recreational divers. Some students of SCUBA often wonder though why they cannot dive with pure oxygen. The reason is because oxygen toxicity would almost surely develop. In fact, even non-recreational divers who dive with gas mixtures other than compressed air need to be wary of the possibility of oxygen toxicity.

The confusing part for some is that it is safe to breath pure oxygen while at normal land pressures, as many do while hospitalized or being treated for various pulmonary problems. The difference is that at normal pressures, the hemoglobin system is able to buffer the amount of oxygen going to the tissues. At increased pressure, pure oxygen would overpower what hemoglobin is able to do, and oxygen levels would increase throughout the body.

The danger of increased oxygen levels is not completely understood, but it is believed to be due to free radicals. Free radicals are molecules that have lost one electron from a pair, and are rendered very reactive. Because free radicals are very reactive, they are constantly looking for another molecule from which they can steal an electron. Once this occurs, that molecule is now a free radical and the process goes on. Free radicals, particularly oxygen, can damage proteins and fats by taking an electron which renders the substance incapable of functioning properly. Our cells are made up of many proteins and fats, so damage to these can cause serious cell damage. The interesting thing is that oxygen free radicals occur all the time. However, we have various enzymes that can take up these free radicals and convert them to a form that is not damaging. When we increase the concentration of oxygen in the body, these enzymes are no longer able to police all of the free radicals and damage can result.

Symptoms of oxygen toxicity can range from pain to twitching, convulsions and even unconsciousness. The range of possibilities is large since there is a breadth of areas that the free radicals can attack. Typically, the first symptoms occur while the diver is still submerged during the dive. Those with possible oxygen toxicity should move to areas of lower pressure to decrease the total amount of oxygen entering their system, and then upon resurfacing they should seek medical attention.

Prevention of oxygen toxicity should involve careful observations of depth and oxygen partial pressures and proper training for the use of gas mixtures. There is no food, drug or vitamin that can reduce one's risk, unlike what some may say. Antioxidants are destroyed during digestion unless you are deficient, as with Vitamin E and C. Finally, although oxygen toxicity is a dangerous condition, not all free radicals are bad. There are some free radicals in our bodies that are necessary for normal functioning and without them we would have trouble moving or fighting infection.

Other Injuries

Swimmer's Ear

Swimmer's Ear is a fairly common problem, that usually does not require medical attention. It is characterized by inflammation and painful infection of the outer ear. Our ears produce a protective cerumen (ear wax) that help to keep moisture out of the ear. However, when we use cotton swabs and other methods of removing the wax, we are allowing moisture and bacteria to enter the outer ear canal. This bacteria can multiply causing an infection and inflaming the surrounding tissue. Fortunately, Swimmer's Ear can often be treated with over the counter ear drops, and/or white vinegar which will help to kill the bacteria. Prevention is even more simple. When diving, one should either dry the ears thoroughly, or place a few drop of vinegar or alcohol in the ears following a dive to help promote drying. If the symptoms are severe, or if you have recurring cases of Swimmer's Ear, medical advice is recommended.

Carbon Monoxide Poisoning & Lipoid Pneumonia

Carbon Monoxide Poisoning and Lipoid Pneumonia are two concerns that are related to the way in which air tanks are filled. Both types of injuries are easily preventable with proper tank filling methods and equipment. Carbon Monoxide Poisoning results from an air tank being filled in an area where the air intake can pull in the exhaust from a motor. Exhaust is usually made up to a large degree by carbon monoxide. When someone dives with a tank that contains a higher than normal amount of carbon monoxide, problems can occur. As we discussed in "Gas Laws", the partial pressure of a gas increases with increases in the overall pressure. Hence, while the amount of carbon monoxide one might breath from the tank at sea level would not be of concern, this amount can increase significantly with depth and pressure. Carbon monoxide is readily picked up by human hemoglobin, a substance that is necessary for the transport of oxygen in the blood. When this occurs, hemoglobin is rendered incapable of carrying oxygen. When a high enough percent of the hemoglobin molecules are taken up by carbon monoxide, hypoxia (low oxygen levels) can occur and tissue death can begin to occur. With persistent or extreme hypoxia, death is even possible.

Lipoid Pneumonia is the result of breathing compressed air that contains oil vapor. Improperly maintenanced air compressors can leak oil which ends up in an air tank as oil vapor upon filling of the tank. When an individual breaths the oil vapors along with the compressed air, it causes a thin layer of oil to form on the inside of the lungs in the alveoli (actual place of gas exchange). The layer of oil decreases the efficiency of gas transfer across the thin alveoli walls. The cilia, or small finger like projections, will attempt to clear the oil deposits away. However, this is usually a timely process and medical attention is indicated.

Risks of Smoking and Diving

While Smoking can not actually be described as a diving injury, it can be a risk factor for some of the diving injuries we have covered. Long term usage of cigarettes can cause pulmonary disease, which obstructs the terminal airways and can produce air-filled dilations. These small spaces of trapped air can expand upon ascent and can increase one's risk of pulmonary barotrauma and arterial gas embolism. Smoking also results in increased bronchial mucous production and paralysis of the cilia. This is a bad combination for divers. The mucous is not being removed, leaving it available to form plugs in the lungs which creates air-filled sacs. Like the air-filled dilations, the sacs can expand and possibly rupture upon ascent. Additionally, most smokers have problems with nasal and sinus drainage. This can greatly increase one's risk of middle ear blocks and middle ear squeeze. Finally, while quitting smoking is a beneficial idea for almost everyone, it can be a problem for divers if done just before a dive trip. When a person stops smoking, mucous production increases for about a period of a week, which as already stated can be a risk factor. The bottom line is, if you love to dive, it is best not to smoke.

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