Decompression Accident (diving Accident, Decompression Sickness)

Decompression accident

Diving is a popular recreational sport. There are always diving accidents. Serious accidents include decompression sickness and pulmonary barotrauma (pressure-related damage to the lung tissue). These so-called decompression accidents occur as a result of the expansion of gas due to the decrease in ambient pressure when surfacing. In the case of barotrauma of the lungs, an overstretching or a tear in the lung tissue can lead, among other things, to the passage of breathing gas into the arterial blood circulation (arterial gas embolism - AGE).

The symptoms can be very similar in both accidents. These include tiredness and breathing difficulties as well as functional disorders of the brain and spinal cord. A decompression sickness must be dealt with immediately. The procedure for decompression sickness and arterial gas embolism is the same.

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• What are the causes of decompression sickness?
• How can you prevent decompression sickness?
• How does a pulmonary barotrauma occur when diving?
• How can you prevent pulmonary barotrauma while diving?
• What symptoms can I experience in a decompression sickness?
• How is the diagnosis made?
• How is treatment in the event of a decompression sickness?
• Whom can I ask?
• How are the costs going to be covered?

What are the causes of decompression sickness?

In the development of decompression sickness (Caisson disease; colloquially diving disease), nitrogen (inert gas) plays a particularly important role. Along with other gases, it is inhaled through the diving bottle and enters the blood through the lungs. At increased ambient pressure, nitrogen dissolves more and more in blood and tissue with increasing depth, but is not metabolized by the body. When rising, nitrogen bubbles form from the dissolved nitrogen as the ambient pressure decreases.

After a dive there are therefore “micro-bubbles” in the body or blood. This can be tolerated well by the body to a certain extent. When ascending slowly, the vesicles slowly enlarge, get caught in the filter of the pulmonary capillaries and are exhaled (normal desaturation process after diving). If you ascend too quickly, the ambient pressure drops quickly. Nitrogen bubbles form, which expand rapidly. If they cannot be exhaled quickly enough, the blisters in the affected organs cause tissue damage and inflammatory reactions.

In the case of massive blistering, the nitrogen bubbles in the blood vessels can combine to form large gas bubbles that block the blood vessels (gas embolism). As a result, areas of the body supplied by these vessels are no longer adequately supplied with blood and are damaged. A distinction is made between arteries and veins (arterial / venous emboli).

Venous embolisms can lead to an interruption in the blood supply to the lungs (pulmonary embolism). This hinders gas exchange (obstruction of the lung capillaries). Pulmonary embolism can cause a lack of oxygen in the body and strain on the right heart. Arterial gas embolism can trigger symptoms such as a stroke, among other things.

In certain malformations of the heart and lungs, however, gas bubbles from the veins can also cause an arterial gas embolism (paradoxical embolism). These malformations are called short-circuit connections (shunts). Blood flows from the veins via a shunt in the heart or in the lungs, bypassing the gas exchange in the lungs, directly into the arterial circulation. A common malformation is the open foramen ovale (PFO - connection between the two atria).

Often affected organs and tissues

• Skin,
• Spinal cord and brain as well
• large joints (pain in the hips, knees, shoulder joints, elbows - colloquially "bends").

Skin symptoms arise from the formation of gas bubbles in the skin tissue, in the veins and lymphatic vessels of the skin, or from subsequent water retention in the tissue (edema). A lack of fluids in the cardiovascular system can also hinder the removal of nitrogen. Severe courses can be associated with the rapid appearance of a cutis marmorata. This is a marble-like discoloration of the skin with bluish, reddish and pale areas, especially on the trunk (stomach, back) and the thighs.

Risk factors for developing decompression sickness

Decompression sickness can occur if you ascend too quickly from depths of over seven to ten meters.

The risk increases depending on:

• longer the diver is under water,
• surfaced faster
• the breaks between dives are shorter,
• the water temperature is colder or
• higher up the diving water.

People who have previously developed decompression sickness are more at risk of developing decompression sickness.

Further risk factors are: strong physical stress, lack of fluids, states of weakness (e.g. during or after an illness), poor adaptation to the environmental conditions (acclimatization - e.g. when diving at the beginning of a trip in tropical regions), drugs that affect the blood, central nervous system (CNS) or have an effect on the cardiovascular system, drug or alcohol consumption and smoking as well as diseases of the central nervous system, the cardiovascular system and the lungs.

A plane trip or a stay in high regions shortly after the dive is also a risk factor.

Note Decompression sickness can occur independently of diving due to a rapid drop in cabin pressure in aircraft and other aircraft in high regions. Gas bubbles also form in the body. However, this rarely happens.

How can you prevent decompression sickness?

Before diving, you should always assess your current physical and mental state and take it seriously. The ingestion of psychoactive substances should be avoided when diving (risk of deep intoxication!). Divers should pay particular attention to adequate hydration before and after a dive. Alcohol should be avoided. Frequent ascent and descent (yo-yo diving) during a dive should be avoided.

No-stop time and decompression breaks

Recreational divers should in principle dive in the so-called no-decompression limit. No-stop time is a period of time that is dependent on the depth of the dive and in which decompression sickness does not usually develop.

When the no-decompression limit is exceeded, slow, controlled ascent allows the dissolved gases to re-enter the blood vessels and to be exhaled through the lungs. So-called decompression breaks - also called decompression stops or decompression pauses / decompression stops - must be observed. Nevertheless, so-called safety stops when surfacing are recommended even within the no-decompression limit.

The diver can read off the no-stop time or the required decompression breaks for a certain diving depth from a decompression table. There are also dive computers that automatically calculate the no-stop time or the number and duration of decompression stops. The required duration of decompression stops depends on:

• the altitude of the diving water (different values apply to mountain lakes than to the sea),
• the diving depth and
• the duration of the dive.

It is safest if a diver stays in the no-stop time or adheres to the most conservative guidelines for decompression breaks.

Note The no-stop time does not take into account the current physical condition of the diver himself!

Adhering to sufficiently long surface breaks is very important! The maximum number of microbubbles in the body is reached after about an hour. For a safe second dive - without the additional risk of gas bubbles from the first dive - a surface interval should be at least two hours.

The development of decompression sickness depends - as mentioned before - on several environmental factors and on the individual daily condition of the diver. Therefore, the development of decompression sickness can never be ruled out, even if the no-decompression limit is strictly adhered to or given decompression breaks.

Flights and stay in high regions

After diving, you should avoid air travel and stay in high regions for a certain period of time (e.g. driving over high mountain passes). Because the higher the region you are in, the lower the ambient pressure you are exposed to. In airplanes, the air pressure in the cabin is reduced to a value that roughly corresponds to air pressure 2,000 meters above sea level.

Recommended waiting times for air travel:

• Twelve hours after a single no-stop dive,
• 24 hours after repeated dives or decompression dives.

Note If a diver develops severe symptoms after a dive, these times do not apply. A diving doctor must be contacted even if the symptoms are mild. This decides how long the diver has to wait before he / she can start a flight again.

How does a pulmonary barotrauma occur when diving?

Pulmonary barotrauma is caused by the expansion of breathing gas in the alveoli (alveoli) due to a rapid drop in pressure when ascending with air hold or “air trapping”. With "air trapping" air cannot be exhaled due to a local narrowing of the bronchi. This “trapped air” can lead to a local overdistension of the lungs when surfacing. Lung diseases that affect exhalation (e.g. COPD and bronchial asthma) can lead to pulmonary barotrauma.

In the case of pulmonary barotrauma (overextension of the lungs) the alveoli can tear and breathing gas can escape from the lung tissue into

• the bloodstream,
• the pleural space (space between the lungs and chest wall) or
• the mediastinum (tissue between the two lungs) or subcutaneous tissue

reach.

The entry of gas bubbles into the bloodstream can lead to an arterial gas embolism (AGE). If these gas bubbles are transported into the brain via the vessels supplying the brain, end arteries can be obstructed. This can lead to neurological symptoms such as those of a stroke. The entry of breathing gas into the pleural space leads to a pneumothorax. The entry of respiratory gas into the mediastinum or the subcutaneous tissue usually does not lead to symptoms. This gas is absorbed (broken down) by the body itself. In some cases it is possible to feel a "crackle" under the skin when you apply pressure.

Risk factors for developing barotrauma of the lungs

Resurfacing with bated breathing occurs primarily in panic situations, when problems cannot be mastered underwater due to insufficient training and practice.

Lung disease with constriction of the bronchi increases the risk of lung overdistension when ascending. In addition, inhaling very dry and cold air can irritate the bronchi and narrow the airways if the airways are overly sensitive. This stimulus can be increased by exertion while diving.

How can you prevent pulmonary barotrauma while diving?

The most important preventive measure is the examination of the lung function as part of a diving fitness test before diving. Divers with chronic lung diseases in particular should have their diving fitness checked regularly by a diving doctor.

Pulmonary barotrauma can be prevented by consistently exhaling while ascending. Regularly practicing the management of emergency situations and emergency ascents serves to prevent panic ascents.

Diving should be avoided during a respiratory tract infection.

What symptoms can I experience in a decompression sickness?

In general, it is important to recognize the symptoms, which can be very similar to the lungs in decompression sickness and barotrauma, and to observe their course closely. Symptoms appear within 24 hours - neurological symptoms in the first few hours - after a dive.

Mild symptoms are itchy skin (diving fleas) or abnormal tiredness.

Among the severe symptoms include:

• Skin spots and changes (cutis marmorata),
• Muscle and joint pain,
• Ant running,
• Numbness,
• Paralysis,
• Voiding disorders,
• physical weakness,
• Difficulty breathing
• Visual, hearing and speech disorders,
• Dizziness,
• Nausea,
• Disturbances in consciousness to unconsciousness as well
• mild symptoms that persist for more than 30 minutes despite breathing oxygen.

Note Chest pain or spitting blood can indicate pulmonary barotrauma, but this does not necessarily have to occur.

How is the diagnosis made?

The diagnosis is made by the emergency doctor or the diving doctor on the basis of the typical complaints after a dive. The assessment is mainly based on:

• the dive profile,
• previous dives,
• Activities during and between dives,
• Fluid status,
• existing diseases,
• ingested medication as well
• the development over time and the current symptoms (Neurocheck - see below).

Imaging methods (e.g. ultrasound, X-ray, CT, MRT), electrocardiograms, and blood and urine tests are mainly used for differential diagnosis. Neurological examinations are required for follow-up. If necessary, special ear, nose and throat medical examination procedures can be used.

How is treatment in the event of a decompression sickness?

If symptoms occur, the diver must never dive again in order to expose himself to the high pressure under water (wet recompression)! The risk of life-threatening consequences of decompression sickness that cannot be treated underwater is too high.

Note Diving partners must also be monitored because they have also had a risky dive and can therefore develop symptoms.

First aid measures

The person concerned should be given 100 percent oxygen or breathing gas with the highest oxygen content available in the situation via a breathing mask and given 0.5 to one liter of liquid per hour to drink. It is best to choose an isotonic drink, not alcoholic drinks. The administration of oxygen supports the removal of nitrogen bubbles from the tissue. In addition, the administration of oxygen leads to an improvement in the oxygen supply to the tissue. The fluid supply normalizes the hemodynamics (blood flow) and facilitates gas exchange via the smallest vessels (capillaries). As a result, nitrogen is released more quickly from the tissue and then exhaled through the lungs.

A small neurocheck is performed regularly to identify neurological symptoms and their changes. Orientation, the function of the cranial nerves and the sensory organs, muscle strength, balance and coordination are checked. Protection against hypothermia or overheating is recommended.

Even with mild symptoms, those affected should be observed for about 24 hours.

Additional first aid treatment if symptoms are severe

If necessary, the usual first aid measures - e.g. lying on the side in the case of impaired consciousness or cardiopulmonary resuscitation in the event of a lack of breathing and cardiac activity - are carried out. If the person concerned cannot breathe independently (rarely!), Artificial ventilation with oxygen / oxygen enrichment should be used. If the person concerned cannot drink himself / herself, the rescue service or the emergency doctor will give the liquid via an infusion.

Treatment in the pressure chamber (decompression chamber)

This treatment is also called HBO (Hyperbaric Oxygen Therapy) therapy. The diving doctor decides on the treatment in a pressure chamber. The transport to the pressure chamber should be carried out as quickly and gently as possible. In the pressure chamber, the person concerned breathes 100 percent oxygen at increased ambient pressure, e.g. at 2.8 bar (pressure unit), corresponding to 18 meters of water depth (hyperbaric oxygenation). This causes the gas bubbles to shrink and finally dissolve. The oxygen supply to the body tissues is restored. The pressure is then slowly reduced to normal air pressure over a period of several hours.

Hyperbaric chamber treatments are carried out until the symptoms have receded as much as possible. If there is no prospect of further improvement, HBO treatments can be stopped. Impairments caused by severe forms of decompression sickness (e.g. with hemiplegia or paraplegia) do not completely regress in individual cases, especially if there is no first aid with oxygen breathing and no rapid pressure chamber treatment.

Medication

At present, with the exception of oxygen, it has not been possible to clearly demonstrate any drug therapy that improves the success of the treatment.

If there is no bleeding and the person concerned cannot move sufficiently, low-molecular heparin is given to thin the blood to prevent thrombosis.

Physiotherapy is started on the third day of treatment at the latest and continued intensively, especially if there is paralysis.

Whom can I ask?

In Austria, the public rescue service (Tel.: 144) coordinates the procedure for diving accidents. When calling, the password "diving accident" should be given. After the initial assessment or care by the emergency doctor, the rescue control centers ensure the emergency transport to the nearest pressure chamber (decompression chamber) if necessary. Before diving abroad, information on country-specific procedures in the event of diving accidents should be obtained.

Several emergency hotlines are available around the clock for questions about a diving accident. Current telephone numbers can be found on the websites of the Austrian Society for Diving and Hyperbaric Medicine (www.oegth.at) and the Austrian Society for Underwater and Hyperbaric Medicine (www.oeguhm.at).

Note After the end of the acute diving accident treatment, further clarification should take place, taking into account the possible causes of the accident and accompanying circumstances. A physical examination for residual damage or impairment is of particular importance. This examination (s) will be carried out by a diving doctor.

How are the costs going to be covered?

All necessary and appropriate diagnostic and therapeutic measures are taken over by the accident and health insurance carriers.

Your doctor will generally settle accounts directly with your health insurance provider. With certain health insurance providers, however, you may have to pay a deductible (treatment contribution) (BVAEB, SVS, SVS, BVAEB). However, you can also use a doctor of your choice (ie doctor without a health insurance contract). For more information, see Costs and Deductibles.

For certain examinations (e.g. MRI), approval from the health insurance provider responsible (medical service - "chief physician") may be required, as well as for certain drug or non-drug treatments (e.g. physical therapy), in some cases only when the disease has reached a certain extent. For certain services (e.g. inpatient stays, aids and medical aids) - depending on the health insurance provider - patient co-payments are provided. Most health insurance providers provide for a permit, sometimes depending on the type of medical aid. The prescription fee has to be paid for medication on a “cash prescription”.

For more information about the respective provisions, please contact your health insurance provider, which you can find on the social security website, for example.