Contents
According to the definition, decompression sickness may affect people who are exposed to large, rapid changes in pressure, i.e. divers using an incorrect ascent technique, pilots of high-speed ascending planes and caisson workers.
The fashion for extreme sports, including diving, expands the circle of people exposed to ailments caused by pressure changes. Incompetent diving and ascent can lead to a barometric injury, i.e. tissue damage due to sudden changes in the volume of gas contained in the body’s spaces.
Specialists distinguish pressure injuries to the lungs, ear, sinuses, intestines and teeth, as well as skin and face, which are caused by gas spaces created by diving equipment.
What is decompression sickness?
Decompression sickness, formerly known as caisson disease, is a group of symptoms that affect a person exposed to external pressure that drops too quickly. This can happen to a diver if he or she comes to the surface too quickly without respecting the proper speed and decompression stops.
If the diver comes to the surface too quickly, the ambient pressure is lowered, causing bubbles of inert gas, usually nitrogen, to form in the body’s tissues and body fluids. According to Henry’s law, if the gas pressure above the surface of the fluid is reduced, the amount of gas dissolved in the fluid is also reduced. The same phenomenon occurs when opening a bottle with a carbonated drink, when you unscrew it, you hear the escaping gas and you can see the formation of carbon dioxide bubbles. They are created as a result of a sudden reduction of the ambient pressure in the bottle to the value of atmospheric pressure. The same is true of nitrogen (an inert gas), which normally occurs in the body’s tissues and body fluids in a harmless dissolved form. During a rapid reduction in pressure, such as an ascent, dissolved gas in the body is released. If the whole process is too fast, the inert gas precipitates out of the blood and forms bubbles. This process is called desaturation.
Half of all decompression sickness cases appear 30 minutes after surfacing. But it can occur up to 36 hours after the end of the dive.
The form of the caisson disease
There are two basic types of decompression sickness.
Type I. It can manifest as joint pain or skin changes. There is pain in the muscles and joints, which mainly affect the large joints, i.e. shoulder, elbow and hip joints. The pain is usually dull but throbbing. The joint hurts when touched, sometimes there is swelling and clear redness. The severe form of the condition forces the diver to adopt unnatural body postures to ease the pain. Pain in joints and limbs occurs in approx. 75%. cases of disease. The cause and mechanism of pain in the joints is unclear. It is believed that the direct cause is nitrogen bubbles growing around (or inside) tendons and ligaments.
In the first type of disease, skin ailments also appear. Vesicles appearing in cutaneous capillaries can cause cutaneous decompression sickness, which is characterized by a red itchy and mottled (marbled) rash that occurs mostly on the arms and chest. Although this type of disease is not dangerous in itself, the presence of the indicated symptoms indicates the possibility of more serious ailments.
Type II Here, the cardiopulmonary and neurological forms of decompression sickness are distinguished.
The cardiopulmonary form is characterized by blockages caused by microbubbles of gas that are found in the vessels of the lungs. Symptoms of this are difficulty breathing, retrosternal pain, rapid and shallow breathing, paroxysmal cough, shortness of breath, and pulmonary edema.
The neurological form, which is considered the most severe form of decompression sickness, causes damage to the spinal cord. There is a sensory disturbance, tingling, skin hyperaesthesia, weakening of the muscles of the legs. In severe cases, paralysis and urination and stool disorders may occur. Loss of consciousness is also possible. Disorders of speech, vision and hearing occur sporadically.
In some cases, alveoli can block blood flow in the venous system, thereby also reducing arterial flow. A spinal cord injury causes numbness and paralysis in the lower limbs. The paralysis quickly progresses to the upper body, down to the neck. Vesicles can also travel to the brain. If they block the blood flow they will cause symptoms similar to a stroke.
Aseptic bone necrosis
It is a late consequence of professional diving or decompression sickness. However, it may also apply to recreational divers, if they experience the so-called cumulative decompression injuries. Then the area of damaged bone tissue enlarges and bone necrosis develops. Unfavorable changes usually concern the area of large joints, especially the head of the femur, proximal epiphysis of the tibia, distal epiphysis of the humerus and proximal epiphysis of the radius. The disease is secretive and quite often manifests itself weeks or months after a dive. The main cause of aseptic osteonecrosis is non-compliance with the rules of decompression and frequent repetition of dives.
First aid
If you suspect decompression sickness, contact your doctor as soon as possible. The only effective method of treatment is therapeutic recompression, i.e. reducing the volume of gas (reducing the size of gas bubbles) in the gas spaces of the body.
What makes you sick?
Fat tissue – a large amount of dissolved nitrogen is stored here. The more body fat there is, the more nitrogen remains in the body after a dive. An obese diver has a greater risk of developing decompression sickness than a lean diver. The role of adipose tissue in recreational diving has not yet been elucidated or clarified.
Age – in the elderly, the circulatory and respiratory systems work less effectively, which hinders gas exchange. With a defective circulatory and respiratory system, an older diver will retain more gas than a young diver.
Dehydration – reduces the amount of blood needed for gas exchange, and therefore slows down the removal of nitrogen from the body. Dehydration is promoted by drinking coffee and drinking alcohol, because water in the body is either quickly excreted (coffee) or used for alcohol metabolism.
Consuming alcohol before or after a dive changes the physiology of the body and this contributes to decompression sickness. Alcohol drunk before diving, even in small amounts, dilates the capillaries and increases circulation, causing more nitrogen to be transported during the dive. While it has the potential to increase the rate of nitrogen release after a dive, it may nevertheless cause adverse changes in microbubble transport.
Cold water – diving in cold water or a suit that is not suitable for the temperature also affects the circulation. At the beginning of a dive, the circulatory system supplies nitrogen to all parts of the body, but defending against heat loss restricts blood flow. Thus, less blood is discharged from dissolved nitrogen during the ascent.
Increased effort – exercise while diving increases circulation, so nitrogen reaches the tissues faster than normal. After rest, your circulation returns to normal, but the slowed circulation does not help remove nitrogen from your body.
Tekst: Anna Jarosz