DIVING AND COMPRESSED AIR INJURIES – DECOMPRESSION SICKNESS. Nitrogen dissolved in the blood and tissues by high pressure produces bubbles as pressure falls, causing decompression sickness. Fatigue and muscular and joint discomfort are common symptoms. Symptoms of the more severe form include numbness, tingling, arm or leg weakness, unsteadiness, vertigo (spinning), difficulty breathing, and chest discomfort, which are similar to those of a stroke. Oxygen and recompression (high-pressure, or hyperbaric, oxygen) therapy are used to treat patients. Limiting dive depth and time, as well as ascend speed, can aid in prevention.
Nitrogen and oxygen make up the majority of air. Each breath taken at depth contains considerably more molecules than a breath taken at the surface because air under high pressure is compressed. Because the body uses oxygen on a constant basis, excess oxygen molecules breathed under high pressure rarely accumulate. The excess nitrogen molecules, on the other hand, do accumulate in the blood and tissues.
Upon the outside pressure drops during a dive or when leaving a compressed air environment, the nitrogen that cannot be breathed creates bubbles in the blood and tissues. These bubbles can enlarge and cause tissue damage, or they can obstruct blood vessels in a variety of organs, either directly or indirectly by causing small blood clots. This blood vessel obstruction produces discomfort and a variety of other symptoms, such as abrupt weakness on one side of the body, difficulty speaking, or dizziness, or even flu-like symptoms. Inflammation is caused by nitrogen bubbles, which cause swelling and pain in muscles, joints, and tendons.
Many of the following factors enhance the likelihood of acquiring decompression sickness:
- Some cardiac anomalies, such as a patent foramen ovale or an atrial septal defect,
- Coldwater
- Dehydration
- Flying after diving
- Exertion
- Fatigue
- Pressure is increasing
- The amount of time spent in a high-pressure setting.
- Obesity
- Older age
- Failure to use proper decompression techniques
Repeated dives within one day are more likely to trigger decompression sickness than a single dive because extra nitrogen remains dissolved in body tissues for at least 12 hours after each dive. Flying within 12 to 24 hours of diving (for example, towards the end of vacation) exposes them to significantly lower air pressure, increasing the risk of decompression sickness.
Nitrogen bubbles can occur in microscopic blood arteries or even in tissues. Because nitrogen dissolves quickly in fats, tissues with high-fat content, such as those in the brain and spinal cord, are more vulnerable.
Type I Decompression illness is typically mild, affecting the joints, skin, and lymphatic vessels.
Type II Decompression illness, which can be deadly, often affects important organ systems such as the brain and spinal cord, as well as the respiratory and circulatory systems.
Symptoms Decompression Sickness
Decompression illness symptoms frequently appear later than those of an air embolism or pulmonary barotrauma. Only half of those suffering from decompression sickness experience symptoms within an hour after surface, but 90% do so within six hours. Symptoms usually appear gradually and take a while to reach their peak effect. The early signs and symptoms may include
- Fatigue
- Loss of appetite
- Headache
- Vague feeling of illness
Type I decompression sickness
Decompression sickness, sometimes known as the bends, is a less severe variant (or musculoskeletal form) of decompression sickness that produces pain. The pain is frequently felt in the joints of the arms or legs, as well as the back and muscles. It can be difficult to establish the exact place at times. At initially, the pain may be slight or sporadic, but it will gradually become greater and more severe. The pain may be acute or characterized as “deep” or “as if something were burrowing into the bone.” When you’re relocating, it’s even worse.
Itching, skin mottling, rash, swelling of the arm, chest, or belly, and excessive weariness are some of the less common symptoms. These symptoms do not endanger life, but they may signal the onset of more serious disorders.
Decompression sickness type II (more severe)
Neurologic symptoms, which can vary from slight numbness to paralysis and death, are the most common symptoms of the more severe form of decompression sickness. The spinal cord is particularly susceptible.
Numbness, tingling, weakness, or a combination of these symptoms in the arms, legs, or both can be signs of spinal cord involvement. Mild tingling or weakness can quickly develop to irreversible paralysis. It’s also possible that you won’t be able to urinate or regulate your urine or defecation. Abdominal and back pain are also frequent.
The majority of the symptoms of a brain embolism are similar to those of an air embolism.
- Headache
- Confusion
- Trouble speaking
- Double vision
When the nerves of the inner ear are compromised, symptoms of inner ear involvement appear, such as severe vertigo, ringing in the ears, and hearing loss.
Cough, chest pain, and progressively worsening trouble breathing are symptoms of lung involvement produced by gas bubbles that migrate via the veins to the lungs (the chokes). Shock and death are possible outcomes in severe cases, which are uncommon.
Late effects of decompression sickness
Decompression sickness can cause dysphoric osteonecrosis (also known as avascular bone necrosis), which can occur in the absence of decompression sickness. It causes bone tissue to be destroyed, particularly in the shoulder and hip. Because of the osteoarthritis that results from the injury, dysphoric osteonecrosis can cause long-term discomfort and incapacity. These injuries are more common among people who work in compressed-air environments and divers who work in deep underwater habitats than among leisure divers. When symptoms do arise, there is often no one initial incident that the person can pinpoint as the cause.
These personnel are subjected to tremendous pressure for lengthy periods of time and maybe suffer from the bends. Technical divers, who dive to deeper depths than recreational divers, maybe more in danger. Dysbaric osteonecrosis normally has no symptoms, but if it occurs near a joint, it can lead to severe, crippling arthritis over months or years. By the time major joint deterioration has developed, joint replacement may be the only option.
Delay or inadequate treatment of spinal cord symptoms frequently results in permanent neurologic issues, such as partial paralysis. However, even with adequate and quick therapy, the damage might occasionally be too severe to repair. Repeated oxygen treatments in a high-pressure chamber appear to aid recovery in some persons with spinal cord injuries.
Diagnosis Decompression Sickness
The nature of the symptoms and their onset in relation to diving help doctors identify decompression sickness. Tests like computed tomography (CT) and magnetic resonance imaging (MRI) can sometimes detect abnormalities in the brain or spinal cord, but they aren’t always accurate. Except in circumstances when the diagnosis is uncertain or the diver’s condition is stable, recompression therapy is started before the findings of a CT or MRI scan are available. Dysbaric osteonecrosis is commonly diagnosed with an MRI.
Prevention
Divers aim to avoid gas bubble formation to avoid decompression sickness. They accomplish this by limiting dive depth and duration to a range that does not require decompression stops during ascent (known as no-stop limits by divers) or ascending with decompression stops as stated in authoritative guidelines, such as the decompression table in Air Decompression, a section in the United States Navy Diving Manual.
The table shows an ascending plan that permits excess nitrogen to escape without causing harm in most cases. Many divers use a portable dive computer to keep track of their depth and time spent underwater. The computer determines the decompression timetable for a safe return to the surface and when decompression stops are required.
Decompression sickness is still a possibility if these precautions are followed. After no-stop dives, a tiny minority of people get decompression sickness. Decompression sickness persists because published tables and computer programs do not fully account for the difference in risk variables across divers, or because some people do not follow the tables’ or computer’s recommendations.
Other precautions are also required:
After several days of diving, it is usual practice to spend 12 to 24 hours (for example, 15 hours) at the surface before flying or ascending to a greater altitude.
Divers who have recovered entirely from moderate decompression sickness should not dive for at least two weeks. It is preferable to wait longer (at least a month) after severe decompression sickness to be assessed by a physician before diving again.
People who get decompression sickness despite following dive table or computer instructions should only dive again after a comprehensive medical examination to rule out underlying risk factors such as heart defects.
Treatment
- Oxygen
- Recompression therapy is sometimes used.
The vast majority of people fully recover. Divers who simply have itching, skin mottling, or exhaustion don’t normally need to recompress, but they should be monitored because more serious problems could develop. It is recommended and may provide relief to breathe 100 percent oxygen through a close-fitting face mask.
Recompression therapy
Any other decompression sickness symptoms signal the need for treatment in a high-pressure (recompression, or hyperbaric oxygen) chamber, as recompression therapy restores normal blood flow and oxygen to afflicted tissues. Following recompression, pressure is progressively lowered with designated breaks to allow surplus gases to leave the body safely. Even patients with just minor or temporary pain or neurologic symptoms are treated because symptoms may recur or worsen during the first 24 hours.
Even if getting to the nearest chamber entails a long journey, recompression therapy may be effective for up to 48 hours or longer after diving. Oxygen is delivered through a close-fitting face mask while awaiting transport, and fluids are given by mouth or intravenously. Treatment delays raise the chance of permanent harm.