cerebral decompression


decompression

 [de″kom-presh´un] return to normal environmental pressure after exposure to greatly increased pressure.cerebral decompression removal of a flap of the skull and incision of the dura mater for relief of intracranial pressure.decompression sickness a condition resulting from a too-rapid decrease in atmospheric pressure, as when a deep-sea diver is brought too hastily to the surface. The popular term bends is derived from the bodily contortions its victims undergo when atmospheric pressure is abruptly changed from a high pressure to a relatively lower one. Called also caisson disease and divers' paralysis. A similar condition, altitude sickness, is suffered by aviators who ascend too rapidly to high altitudes. Decompression sickness may also be a complication in a type of oxygen therapy called hyperbaric oxygenation, in which the patient is placed in a high-pressure chamber to increase the oxygen content of the blood. Personnel and the patient within the chamber must be protected from decompression sickness when they emerge from the high-pressure chamber.Cause. The phenomenon of decompression sickness is explained in terms of a law of physics: The greater the atmospheric pressure, the greater the amount of gas that can be dissolved in a liquid. The gas involved in this condition is the air we breathe, composed chiefly of nitrogen and oxygen. Under normal atmospheric pressure, nitrogen is present in the blood in dissolved form. If the atmospheric pressure is substantially increased, a proportionately greater amount of nitrogen will be dissolved in the blood. The same is true of oxygen, and this is the basis for hyperbaric oxygenation in the treatment of oxygen deficiency.
The increase in pressure causes no ill effects. Nor will there be any ill effects if the pressure is gradually brought back to normal. When the decrease in pressure is slow, the nitrogen escapes safely from the blood as it passes through the lungs to be exhaled. If the pressure drops abruptly back to normal, the nitrogen is suddenly released from its state of solution in the blood and forms bubbles. Although the body is now under normal air pressure, expanding bubbles of nitrogen are present in the circulation and force their way into the capillaries, blocking the normal passage of the blood. This blockage (or air embolus) starves cells dependent on a constant supply of oxygen and other blood nutrients. Some of these cells may be nerve cells located in the limbs or in the spinal cord. When they are deprived of blood, an attack of decompression sickness occurs.
The oxygen in the blood reacts similarly when abnormal pressure is abruptly relieved. But because oxygen is dissolved more easily than nitrogen, and because some of the oxygen combines chemically with hemoglobin, the oxygen released in decompression forms fewer bubbles, and is therefore less troublesome.Symptoms and Treatment. Symptoms include joint pain, dizziness, staggering, visual disturbances, dyspnea, and itching of the skin. Partial paralysis occurs in severe cases; collapse and insensibility are also possible. Only rarely is decompression sickness itself fatal, although a diver while in this condition may suffer a fatal accident unless he or she is rescued. Treatment consists of placing the victim in a decompression chamber where the air pressure is at the original higher level of pressure. If the victim is a diver, this is the pressure at the depth where he or she was working. Pressure in the chamber is then reduced to normal at a safe rate.

ce·re·bral de·com·pres·sion

removal of a piece of the cranium, with incision of the dura, to relieve intracranial pressure.

ce·re·bral de·com·pres·sion

(ser'ĕ-brăl dē-kŏm-presh'ŭn) Removal of a piece of the cranium, usually in the subtemporal region, with incision of the dura, to relieve intracranial pressure.