Oxygen is indispensable for maintaining life on Earth. Its optimal content in the inhaled air for a person is 20–21%. Oxygen mixtures with its increased content are used to maintain the respiratory function when immersed in water, in conditions of rarefied air and outer space. In medicine, oxygen therapy is used to treat a number of diseases.
For any living organism, both deficiency and excess oxygen are dangerous. What is hyperoxia, under what conditions does this disease develop and how is it dangerous for humans?
What is hyperoxia
Hyperoxia is a complex of pathological reactions that develops in the body with an excessive supply of oxygen. The disease occurs when improper use of respiratory mixtures when diving to a depth (oxygen poisoning in diving), in aviation and astronautics, during oxygen treatment (hyperbaric oxygenation).
Factors that aggravate the course of the disease:
- overheating or overcooling;
- physical activity;
- individual sensitivity;
- the content of harmful gases in the respiratory mixture, including carbon dioxide;
- carbon dioxide accumulation in the body.
Oxygen poisoning, possibly due to the use of regenerative breathing apparatus, from improper use of the pressure chamber during decompression.
With a slight glut of tissues with oxygen, oxygen intoxication can develop, which is accompanied by:
- clouding of consciousness;
- a veil before eyes;
A similar condition occurs when hyperventilation of the lungs (forced deep breaths and exhalations), or an unusual increase in the oxygen content in the atmospheric air — for example, in urban residents when going out of town. In athletes, a similar situation can be observed with high physical exertion simultaneously with deep breathing.
Signs of hyperoxia
When an excess amount of oxygen enters the bloodstream, normal compensatory reactions develop first:
- slow breathing;
- narrowing of the brain and lung vessels;
- decrease in heart rate;
- decrease in circulating blood volume.
In the future, pathological processes occur, manifested in the violation of the transfer of gases by blood and oxidation of cell membranes.
Normally, blood from the lungs transports oxygen, back from the tissues - carbon dioxide. An excess of oxygen leads to its binding to hemoglobin, and there is not enough free hemoglobin to remove carbon dioxide. Therefore, there is a poisoning of tissues with carbon dioxide. This is manifested by the following features:
- redness of the face;
- loss of consciousness.
The second pathological mechanism of oxygen poisoning is associated with the destruction of cell membranes. Normally, oxygen is completely oxidized in tissues, and when it is in excess, many oxidized products remain - free radicals, which begin to interact primarily with the lipids of cell membranes. A cascade process starts, which can continue even after normalization of the oxygen level in the tissues.
Symptoms of oxygen poisoning
Oxygen intoxication manifests itself instantly, that is, there is no hidden period. An excess of oxygen in the body leads to the following symptoms:
convulsions may be the only sign - a consequence of the rapid poisoning of the central nervous system with a high content of oxygen;
- the first symptoms of poisoning are most often numbness or tingling of the fingers, twitching of the muscles of the face, trembling of the lips;
- recurrent nausea and vomiting;
- blurred vision, even blindness;
- anxiety, anxiety, irritability, confusion;
- tinnitus, sometimes pulsating, or similar to the sound of a bell;
- dizziness, incoordination of movements.
Symptoms of a disease depend on its form.
Forms of oxygen poisoning
Depending on the prevalence of certain symptoms in oxygen poisoning, there are three forms of the disease.
- Pulmonary form. This form affects mainly the respiratory tract and lungs. It is characterized by swelling and irritation of the mucous membrane, cough, burning sensation behind the sternum. With increasing symptoms, hemorrhages develop in the internal organs, brain and spinal cord, atelectasis (collapse) of the lungs. It is possible with prolonged breathing with a mixture with a low partial pressure of oxygen of 1.3–1.6 bar (for example, descent to a depth of 18 meters). The rate of reaction is proportional to the partial pressure and time of inhalation of the mixture. Thus, with a partial pressure of oxygen of 1 bar, hyperoxia in a person occurs after 6 hours, and at 2.5 bar - after 3. When the causes are eliminated, the symptoms disappear in 2-4 hours, the body finally recovers in 2-4 days.
Convulsive form. Develop hearing and vision impairment, irritability, tingling and muscle twitching. With an increase in hyperoxia, there are increasing seizures like epileptic seizures. Under water, the risk of drowning is high. The convulsive form is characteristic of poisoning with pure oxygen or mixtures with a partial pressure of 2–3 bar. When eliminating the causes of hyperoxia after cramps, sleep occurs, which can last for several hours. After a seizure, there are no adverse events.
- Vascular form. It develops with a partial pressure of more than three bars. It is characterized by a sharp drop in blood pressure, numerous hemorrhages in the skin and mucous membranes, arrest of cardiac activity.
With a partial pressure of 5 bar, hyperoxia develops rapidly, there is an instant loss of consciousness and death occurs.
In diving practice, you can encounter pulmonary and convulsive forms of hyperoxia, as well as their mixed course.
First aid is to eliminate excess oxygen:
- reduce the depth of descent and move to a stop;
- in case of loss of consciousness, bring the victim to his senses (experienced divers for this purpose use a strong stream of oxygen, the flow of which reflexively intercepts breath);
- in the chamber switch to breathing an oxygen-depleted mixture or air;
- in case of convulsions to protect from damage, but not to fix;
- decompression can not be performed with convulsions;
- during the day bed rest in a warm darkened room with good ventilation.
In severe cases of oxygen poisoning, medical intervention may be necessary.
Treatment is determined by the doctor based on the nature of hyperoxia.
- In the case of the lung form, venous strands are applied to the extremities, suction of the foam from the lungs is performed, acidosis is treated, and diuretic agents are used.
- For removal of seizures, intravenous "Aminazin", "Seduxen" or "Dimedrol" is used.
- If there are appropriate indications, - prescribe funds to restore cardiac activity, stimulate breathing and painkillers.
An antibiotic may be prescribed to prevent pneumonia.
Prevention of hyperoxia is in compliance with the rules for the use of oxygen mixtures and the use of breathing apparatus:
- do not exceed the permissible immersion depth;
- do not exceed the allowable time at the depth;
- when using mixtures with different oxygen content, strictly follow the marking of cylinders and the order of their use;
- observe the time spent in the decompression chamber;
- during decompression with pure oxygen, the breathing time should not exceed 3–3.5 hours;
- regularly check the technical serviceability of regenerative devices.
Let's sum up. Hyperoxia is a pathological reaction that develops with an excess of oxygen in the body. The disease develops when breathing pure oxygen or its mixtures. In practice, divers, pilots and astronauts often suffer from the manifestation of symptoms of hyperoxia. Also, perhaps, the development of the disease in patients undergoing treatment in the pressure chamber.
Signs of oxygen poisoning include dizziness, blurred vision, tingling in the fingers and toes, and trembling of the lips. In the future, convulsions or disorders in the respiratory organs develop. With the timely elimination of excess oxygen, the symptoms disappear within a few hours, and the body is fully restored after a few days. In severe cases, the victim needs medical assistance.