Swimming Pool Blackout

In a pool blackout, a diver loses consciousness underwater and mostly inhales water. This event is life-threatening and affects freedivers in particular. Immediate rescue from the water, in combination with intensive care measures, can save the life of the person concerned.

Swimming Pool Blackout

What is a pool blackout?

Swimming pool blackout is unconsciousness caused underwater by a lack of oxygen to the cerebral brain. The ascent blackout, which primarily affects no-limits freedivers, must be distinguished from this phenomenon. This phenomenon is caused by similar processes as the swimming pool blackout. Therefore, the ascent blackout is sometimes understood as a special form of the swimming pool blackout. See beautyphoon for What is Hyperbilirubinemia.

As a rule, the pool blackout is also associated with a dive that is deliberately hyperventilated before. When diving, the oxygen content in the blood continues to drop. This increase forms the basis of unconsciousness. In extreme cases, the pool blackout results in death by drowning.

Such extreme variants occur especially with divers who are traveling alone. The swimming pool blackout is one of the most common causes of death in diving and also often causes death by drowning outside of diving, which affects around 400 to 600 people in Germany every year.


A rising carbon dioxide content in the arterial blood results in a respiratory stimulus that becomes continuously more intense and cannot be boycotted above a certain concentration. As a rule, the oxygen content in the blood drops at the same time when diving and, above a certain threshold, results in cerebral unconsciousness. However, long before this fainting occurs, the average person surfaces to inhale because of the increasingly intense breathing stimulus.

However, the breathing reflex above a certain carbon dioxide content can be shifted backwards through training. When the rising carbon dioxide level no longer causes a rising respiratory reflex, then fainting from a falling oxygen level hits the diver completely unexpectedly and without warning. Despite being unconscious, above a certain level of carbon dioxide, a breath is taken and the diver inhales water.

Symptoms, Ailments & Signs

The swimming pool blackout can cause various symptoms afterwards. Carbon dioxide poisoning with symptoms such as cramps, headaches, tachycardia and shortness of breath can set in afterwards, for example. If there is an insufficient supply of oxygen, cells usually die irreversibly, since their cell metabolism cannot be maintained without oxygen.

Thus, at worst, a pool blackout can kill off massive portions of the brain, resulting in a coma or even death. The aspiration of water as part of the pool blackout can allow more or less water to get into the lungs. This is how pulmonary edema develops, which causes shortness of breath with shallow breathing, as well as chest pain and a severe cough.

Bubbling sounds can be heard when breathing. The lips turn blue because the body’s oxygen supply is permanently reduced. Bloody or foamy sputum from the lungs can also occur as part of pulmonary edema.

Diagnosis & course of disease

A diagnosis does not have to be made for a swimming pool blackout. The phenomenon does not describe a medical condition, but rather an emergency event. The doctor must find out the consequences of a swimming pool blackout on a case-by-case basis. He assesses the consequences of unconsciousness under water using brain wave measurements, various types of imaging and the patient’s vital signs.

The course of a swimming pool blackout depends primarily on how quickly the diver is rescued from the water and how much water he has inhaled. If the oxygen supply is cut off for too long, coma or death will result.


A swimming pool blackout can have serious consequences. First and foremost, there is a risk that the person affected will drown as a result of the unconsciousness. If there are no witnesses or first responders on site, this is almost always fatal. If you intervene quickly, the complications depend on how long the person has been underwater. If brain cells have already died, permanent brain damage cannot be ruled out.

Even with a good course, neurological and mental deficits remain, at least temporarily. Various complications can arise as a result of a swimming pool blackout. As a result of carbon dioxide poisoning, seizures, headaches, tachycardia and shortness of breath usually occur. Aspiration of water can cause pulmonary edema associated with difficulty breathing, severe coughing, and other complications. In extreme cases, the person affected suffocates and must be revived immediately.

Performing cardiopulmonary resuscitation can result in rib or sternum fractures and liver and spleen injuries. If air enters the area between the pleura and the lining of the lungs, it can cause vomiting and aspiration. Typically, adrenaline or norepinephrine is also given, which can cause cramps, dizziness, and gastrointestinal distress.

When should you go to the doctor?

A swimming pool blackout must always be treated immediately by a doctor. If left untreated, the affected person usually dies, so that a very quick diagnosis with quick treatment has a positive effect on the further course of the disease. A doctor should be consulted if the person concerned becomes short of breath. This usually leads to a blue discoloration of the skin and severe headaches or heart palpitations.

Those affected can also suffer from cramps. If these symptoms occur under water, the water must be left immediately. On land, too, the symptoms indicate a swimming pool blackout and must be treated by a doctor. An ambulance or hospital should be called immediately to prevent further complications and irreversible cell death. The sooner the doctor is called, the better the further course.

Treatment & Therapy

In the event of a pool blackout, first responders will pull the diver out of the water and revive them if necessary. The resuscitation corresponds to the conventional cardiopulmonary resuscitation. If water is inhaled, ideally the patient will vomit the water. He should therefore be either in a sitting position or in a stable side position in order not to choke on the vomited water.

The affected person is usually protected from cooling down with blankets. In addition to 100 percent oxygen, the emergency doctor administers catecholamines such as adrenaline or nordadrenaline to the patient. Further treatment of the patient takes place in the hospital. Carbon dioxide poisoning is counteracted by mechanical ventilation. The goal is to establish a positive airway pressure.

Intensive medical care is usually indicated. The patient’s respiration and vital signs are closely monitored in the intensive care unit. Blood gases are also analyzed for at least one day. If necessary, regulatory steps will be taken. These regulatory steps consist of ventilation, medication or infusions.

Depending on the condition of the central nervous system, the patient may have to undergo long-term physiotherapy treatment in order to relearn any motor skills after necrosis of the brain tissue. Speech therapy can also make sense depending on the location of the dead cells.


Hyperventilation is used to increase the distances, especially when diving for distances without the aid of equipment. This procedure is associated with danger to life. Divers should therefore either not accept this sporting challenge at all or at least under supervision. In general, diving is only recommended in a group. Diving alone carries particularly high risks and often ends in death.


In the case of a swimming pool blackout, the aftercare measures are in most cases significantly limited, since the person concerned has to be transported out of the water and revived. Therefore, the priority with this disease is a quick reaction and the rescue of a diver to prevent further complications, discomfort and, in the worst case, death of the affected person.

As a rule, an ambulance should be called immediately so that the person concerned can be treated quickly and correctly. After treating the swimming pool blackout, the patient should definitely take it easy and rest. Efforts and physical or stressful activities should be avoided in order not to unnecessarily burden the body.

In some cases, the help and care of the patient from their own family is also necessary to make everyday life easier for the person concerned. Likewise, after a swimming pool blackout, the cause of the complaint should be clarified, although in some cases further treatment is necessary. As a rule, there is no reduced life expectancy if the affected person is treated in good time. However, the further course depends heavily on the time of the rescue.