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Symptoms and Signs of Decompression Syndromes: The Bends

Doctor's Notes on The Bends
(Decompression Syndromes)

The bends, also known as decompression sickness (DCS) or Caisson disease is a condition that occurs in scuba divers when dissolved gases (mainly nitrogen) come out of solution in the bloodstream, forming gas bubbles in the circulation. It is caused by rapid changes in pressure during scuba diving. The bends can affect almost any area of the body or any organ, including the lungs, heart, brain, joints, and skin.

The most common signs and symptoms of the bends include joint pains, fatigue, low back pain, paralysis or numbness of the legs, and weakness or numbness in the arms. Other associated signs and symptoms can include dizziness, confusion, vomiting, ringing in the ears, head or neck pain, and loss of consciousness.

Medical Author:
Medically Reviewed on 3/11/2019

The Bends
(Decompression Syndromes) Symptoms

The nervous and musculoskeletal system are most often affected. If a diver is going to develop symptoms they will show within 48 hours in all cases. Most have symptoms within 6 hours, while some develop within the first hour of surfacing from a dive.

DCS is often categorized into two types. Type I indicating mild symptoms and Type II with neurologic and other serious symptoms.

Symptoms of the bends include the following:

Musculoskeletal Symptoms (most common symptoms)

  • Pain in and around major joints with the shoulder and elbows being the most commonly affected in divers but any joint can be involved due to nitrogen being released into the joints and muscles.

Fatigue

  • Extreme tiredness that is out of proportion to the activity just performed.

Skin

  • Rashes that are red or marbled may occur. They can be very itchy also.
  • It is rare to have skin findings with DCS

Itching (also known as "the creeps")

  • Seen more commonly during decompression in hyperbaric chamber workers (see media photos).
  • Very itchy reaction on the skin that is exposed to pressures of the dive (i.e. not covered up by a wet suit.)
  • This is due to gas from the chamber dissolving into the skin and forming bubbles under the skin.
  • The creeps do not occur in divers

The Chokes (pulmonary or lung decompression sickness)

  • Rare but if it occurs can be very serious
  • A burning pain in the chest that is usually worse with breathing in (inspiration).
  • Other symptoms include cough, difficulty breathing, and cyanosis (blue lips and skin)
  • Divers with the chokes can progress to shock rapidly

Neurologic Decompression Sickness (these symptoms may be the only DCS signs)

  • The most common area affected in divers is the spinal cord.
  • Symptoms classically include low back pain, "heaviness" of the legs, paralysis and/or numbness of the legs, and even loss of control of the sphincter (or valve) that controls urine and stool resulting in incontinence.
  • Other symptoms may include fatigue, weak or numb upper extremities, chest or abdominal pains.
  • DCS involving the brain can present with dizziness, confusion, decreased awareness, loss of consciousness, loss or limited vision and even difficulty with balance and/or walking.

Lymph nodes (glands)

The lymph glands can be swollen and painful.

Pain

Pain can occur at the head, neck, or torso. Pain at these sites versus the arms or legs carries a worse prognosis.

Staggers

Occasionally someone with decompression illness may have symptoms suggesting an inner ear problem, such as a spinning sensation, deafness, ringing in the ears, or vomiting. This group of symptoms is called the "staggers."

The Bends
(Decompression Syndromes) Causes

Nitrogen or any gas from a diver's air tank increases in pressure as a diver descends. For every 33 feet in ocean water, the pressure due to nitrogen goes up another 11.6 pounds per square inch,. As the pressure due to nitrogen increases, more nitrogen dissolves into the tissues. The longer a diver remains at depth, the more nitrogen dissolves. Unlike the oxygen in the air tank a diver uses to swim underwater, the nitrogen gas is not utilized by the body and builds up over time in body tissues. The underlying cause of symptoms throughout the body is due mainly to nitrogen bubbles being released when the diver returns to sea level and blocking blood flow and disrupting blood vessels and nerves by stretching or tearing them. They may also cause emboli, blood coagulation and the release of vasoactive compounds.

A clear example to illustrate this bubble formation process is that of a bottle of carbonated soda. A bottle of carbonated soda is filled with gas (carbon dioxide), which cannot be seen because it is dissolved in solution under pressure. When the bottle is opened, the pressure is released and the gas leaves the solution in the form of bubbles. A diver returning to the surface is similar to opening the bottle of soda. As a diver swims to the surface, the pressure decreases. The nitrogen, which has dissolved in tissues, wants again to leave, because the body can hold only a certain amount based on that nitrogen pressure.

  • If a diver surfaces too fast, the excess nitrogen will come out rapidly as gas bubbles. Depending on which organs are involved, these bubbles produce the symptoms of decompression sickness.
  • The risk of decompression illness is directly related to the depth of the dive, the amount of time under pressure, and the rate of ascent. Dive tables, such as the US Navy Dive Tables, provide general guidelines as to what depths and dive times are less risky for the development of decompression sickness.

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REFERENCE:

Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.

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