When does decompression sickness occur

When underwater, divers breathe compressed air that contains nitrogen gas at the same pressure as the surrounding water. This accumulates in the diver's body tissue, and is breathed out on ascent, providing that ascent occurs at a safe rate. DCS may occur even if a person dives within the limits of their dive computer or decompression tables and even if they complete a safety stop. If a diver swims to the surface too quickly, and holds their breath while doing so a rapid breath hold ascent , the resulting reduction in the ambient pressure can cause their lungs to over-inflate.

These air bubbles can block the flow of blood to different parts of the body, which is called arterial gas embolism AGE.

Unusual symptoms occurring within 48 hours after diving should be presumed to be DCI until proven otherwise. The onset of DCI symptoms after 48 hours is unusual unless provoked by ascent to altitude, that is flying. Divers with suspected DCI should be kept lying flat and given oxygen if it is available. All other normal first aid measures should be taken as required.

It is important you rest and drink lots of fluids. Alcohol should be avoided as it can cause dehydration. If you have aches and pains between your hyperbaric treatments you can take paracetamol or an anti-inflammatory drug, such as aspirin or ibuprofen. Multiple dives on the same day and yo-yo diving a series of dives that have short periods of time at depth alternating with similar short periods at the surface increases your risk of DCI.

Flying or climbing to an altitude greater than m should be avoided for 4 to 6 weeks to avoid recurrence of symptoms. This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional.

Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.

In these cases, there is time for a more thorough evaluation by a diving medical specialist to rule out other causes. Like DCS, mild symptoms may appear to be due to causes other than diving, which can delay treatment.

Symptoms may resolve spontaneously, and the diver may not seek treatment. The consequences of this are similar to untreated DCS. Residual brain damage may occur, making it more likely there will be residual symptoms after a future AGE — even after treating the later instance. The most common manifestations of DCS are joint pain and numbness or tingling.

The next most common are muscular weakness and inability to empty a full bladder. Severe DCS is easy to identify because the signs and symptoms are apparent. However, most DCS manifests subtly with a minor joint ache or paresthesia an abnormal burning or tingling sensation in an extremity. Note: Signs and symptoms usually appear within 15 minutes or up to 12 hours after surfacing.

In severe cases, symptoms may appear before surfacing or immediately afterward. Delayed onset of symptoms is rare but can happen, especially if air travel follows diving. In many cases, these symptoms are ascribed to another cause such as overexertion, heavy lifting or even a tight wetsuit.

Sometimes these symptoms remain mild and resolve by themselves, but they may increase in severity until it is obvious that something is wrong and help is needed. Recreational divers should dive conservatively, whether they are using dive tables or computers. Experienced divers sometimes select a table depth rather than actual depth of 10 feet 3 meters deeper than called for by standard procedure.

This practice is recommended for all divers, especially when diving in cold water or under strenuous conditions. Divers should be cautious about approaching no-decompression limits, especially when diving deeper than feet 30 meters.

Avoiding the risk factors described above will decrease the risk of DCS. Flying or other exposure to altitude too soon after diving can also increase the risk of decompression sickness as explained in Flying After Diving. Always relax and breathe normally during ascent. Lung conditions such as asthma, infections, cysts, tumors, scar tissue from surgery, or obstructive lung disease may predispose a diver to AGE. If you have any of these conditions, consult a physician with experience in diving medicine before you dive.

The treatment for decompression illness is recompression. It is essential that a diver with AGE or severe DCS to be stabilized at the nearest medical facility before being transported to a chamber. Early oxygen first aid is essential and may reduce symptoms, but this should not change the treatment plan. Always contact DAN or a physician trained in dive medicine in cases of suspected decompression illness — even if the signs and symptoms appear resolved.

Delays in seeking treatment elevate the risk of residual symptoms. Over time the initially reversible damage may become permanent. After a delay of 24 hours or more, treatment may be less effective, and symptoms may not respond. Even if there has been a delay, consult a diving medical specialist before making any conclusions about possible treatment effectiveness. There may be residual symptoms after treatment. Soreness in and around an affected joint is common and usually resolves in a few hours.

If the DCI was severe, there could be significant residual neurological dysfunction. Follow-up treatments, along with physical therapy, can help. The usual outcome is eventual complete relief from all symptoms with prompt treatment.

With severe DCS, you may have a permanent residual effect such as bladder dysfunction, sexual dysfunction or muscular weakness, to name a few. However, the extra nitrogen molecules do accumulate in the blood and tissues. As outside pressure decreases during ascent from a dive or when leaving a compressed air environment, the accumulated nitrogen that cannot be exhaled immediately forms bubbles in the blood and tissues.

These bubbles may expand and injure tissue, or they may block blood vessels in many organs—either directly or by triggering small blood clots. This blood vessel blockage causes pain and various other symptoms, for example, sometimes similar to those of a stroke such as sudden weakness on one side of the body, difficulty speaking, or dizziness , or even flu-like symptoms.

Nitrogen bubbles also cause inflammation, causing swelling and pain in muscles, joints, and tendons. Certain heart defects, such as patent foramen ovale or atrial septal defect Atrial and Ventricular Septal Defects Atrial and ventricular septal defects are holes in the walls septa that separate the heart into the left and right sides.

Holes can be present in the walls of the heart between the upper heart Because excess nitrogen remains dissolved in the body tissues for at least 12 hours after each dive, repeated dives within 1 day are more likely to cause decompression sickness than a single dive. Flying within 12 to 24 hours after diving such as at the end of a vacation exposes people to an even lower atmospheric pressure, making decompression sickness slightly more likely. Nitrogen bubbles may form in small blood vessels or in the tissues themselves.

Tissues with a high fat content, such as those in the brain and spinal cord, are particularly likely to be affected, because nitrogen dissolves very readily in fats. Type I decompression sickness tends to be mild and affects primarily the joints, skin, and lymphatic vessels. Type II decompression sickness, which may be life-threatening, often affects vital organ systems, including the brain and spinal cord, the respiratory system, and the circulatory system.

Symptoms of decompression sickness usually develop more slowly than do those of air embolism Arterial Gas Embolism Arterial gas embolism is blockage of blood supply to organs caused by bubbles in an artery. It is a leading cause of death among underwater divers, such as scuba divers, who breathe compressed The lungs, gastrointestinal tract, part of the face covered Symptoms commonly begin gradually and take some time to reach their maximum effect.

The first symptoms may be. The less severe type or musculoskeletal form of decompression sickness, often called the bends, typically causes pain. The pain usually occurs in the joints of the arms or legs, back, or muscles. Sometimes the location is hard to pinpoint. The pain may be mild or intermittent at first but may steadily grow stronger and become severe. Less common symptoms include itching, skin mottling, rash, swelling of the arm, chest, or abdomen, and extreme fatigue.

These symptoms do not threaten life but may precede more dangerous problems. The more severe type of decompression sickness most commonly results in neurologic symptoms, which range from mild numbness to paralysis and death. The spinal cord is especially vulnerable. Symptoms of spinal cord involvement can include numbness, tingling, weakness, or a combination in the arms, legs, or both. Mild weakness or tingling may progress over hours to irreversible paralysis.

Inability to urinate or inability to control urination or defecation may also occur. Pain in the abdomen and back also is common. Symptoms of brain involvement, most of which are similar to those of air embolism, include. Symptoms of inner ear involvement, such as severe vertigo, ringing in the ears, and hearing loss, occur when the nerves of the inner ear are affected. Symptoms of lung involvement caused by gas bubbles that travel through the veins to the lungs, produce cough, chest pain, and progressively worsening difficulty breathing the chokes.

Severe cases, which are rare, may result in shock and death.