Breathing gas (any gas) under pressure can present a myriad of possible medical problems. The most common of these decompression sickness or "the bends," caused by breathing gases under pressure which are then not metabolized by the body.

Doctors first described decompression sickness as caisson disease, because workers building bridges in pressurized air boxes called caissons developed symptoms of the then-mysterious illness. Because of the strange position these workers put themselves due the pain they were in, they looked like a popular fashion style of the day - the Grecian Bend. They had "the bends" and the name has stuck.

In the United States, more than 500 people suffer from decompression sickness each year. In Thailand more than 300 people are treated - though many more cases go undiagnosed. 


Well over half of divers report symptoms decompression illness within 1 hour of surfacing from the dive. These can be mild or severe. The majority of divers (95%) will show symptoms within 6 hours. Almost all divers (99%) show symptoms within 24-48 hours. Due to nitrogen bubbles released during ascent or surfacing - there can be damage by mechanically obstructing blood flow. These bubble can also cause a local chemical disruption of the vascular beds

The Symptoms of Decompression Illness



The most common Symptom -  joint pains involving the arms or legs. Intensity varies from mild to severe. Arms are more commonly involved than legs. The pain is usually most prominent around joints and is sometimes relieved by direct pressure. This occurs because nitrogen is released into the joints and muscles.

 Itching: Skin itching usually goes away by itself but may progress to include other symptoms of decompression illness.

Skin: Rashes can be red or marbled. They can be accompanied by itching.

Lymph nodes: They 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.

Nervous system: Someone with decompression illness often has nervous system complaints, such as weakness on one side of the body, numbness, pains shooting down an arm or leg, inability to urinate or defecate, or other strokelike symptoms. This occurs because nitrogen bubbles released into the circulation obstruct blood flow in areas of the brain or spinal cord.

Chokes: Decompression illness rarely causes breathing systems problems called the "chokes." Symptoms include burning chest pain, cough, and shortness of breath.

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 Causes

    Nitrogen 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, or 600 torr. As the pressure due to nitrogen increases, more nitrogen dissolves into the tissues. The longer a diver remains at depth, the more nitrogen dissolves for any specific depth. 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.

  • A clear example to illustrate this 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 due to nitrogen 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 process is similar to shaking a can of carbonated soda. If the pressure is high enough, the carbon dioxide in the soft drink will emerge upon opening the can as a gush of bubbles.

    • 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. Much of this data was gleaned from actual human divers in experimental diving units.

    • The Bends Symptoms

      Well over half of divers with decompression illness report symptoms within 1 hour of surfacing from the dive. Some 95% of victims show symptoms within 6 hours. Almost all show symptoms within 24-48 hours. The nitrogen bubbles released during surfacing cause damage by mechanically obstructing blood flow. Additionally, they cause a local chemical disruption of the vascular beds.

      Specific symptoms include these:

    • The bends: The bends are joint pains involving the arms or legs. Intensity varies from mild to severe. Arms are more commonly involved than legs. The pain is usually most prominent around joints and is sometimes relieved by direct pressure. This occurs because nitrogen is released into the joints and muscles.
  • Itching: Skin itching usually goes away by itself but may progress to include other symptoms of decompression illness.

  • Skin: Rashes can be red or marbled. They can be accompanied by itching.

  • Lymph nodes: They 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.
  • Nervous system: Someone with decompression illness often has nervous system complaints, such as weakness on one side of the body, numbness, pains shooting down an arm or leg, inability to urinate or defecate, or other strokelike symptoms. This occurs because nitrogen bubbles released into the circulation obstruct blood flow in areas of the brain or spinal cord.
  • Chokes: Decompression illness rarely causes breathing systems problems called the "chokes." Symptoms include burning chest pain, cough, and shortness of breath.
  • 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."

When to Seek Medical Care

Any victim reporting signs or symptoms of decompression illness that began within 48 hours of scuba diving should be seen by a doctor at an emergency care facility.

The doctor will likely presume that a victim reporting symptoms within 48 hours of surfacing from a scuba dive to have decompression illness. It is important to inform the doctor of your recent diving experience and its temporal relation to your symptoms.

 

The Bends Treatment

Self-Care at Home

Rescue the diver from the water and provide emergency care within the limits of your training.

  • Dry and rewarm the diver with blankets if hypothermic (drop in body temperature).
  • You can visit the Divers Alert Network Web site or call them in the United States at (919) 684-8111 to determine where the nearest hyperbaric chamber is located.
  • Transport the person in a supine position (horizontal, lying on their back) to an emergency care facility. If a hyperbaric chamber is available, you may coordinate to transport directly to that facility for definitive care.
  • If you must use air transport, attempt to find an air frame that can transport the diver at below 1,000 feet or pressurize the cabin to sea level pressure. Use high-flow oxygen if it is available during transport.

Medical Treatment

The doctor will first treat immediate life threats, such as breathing problems or shock, if present.

  • The diver will need high-flow oxygen and IV fluids. Blood and urine will be sent for laboratory tests to assess any blood clotting problems and hydration status.
  • The diver will need to go to a hyperbaric chamber (for many divers or a single chamber) for recompression. During this process the chamber becomes pressurized with air and oxygen based on prearranged protocols to simulate pressure depths of 30-60 feet. Typical dives last 140-270 minutes, but may last longer. At this depth or chamber pressures, bubbles are reduced in size or reabsorbed to ensure adequate blood flow. Recompression prevents further bubble formation and provides high amounts of oxygen to the injured tissues. Further treatments depend on how the diver responds to the initial treatment.
  • Often the person is admitted to the hospital to monitor medical condition and to ensure that there is no recurrence of symptoms.

Follow-up

Follow up immediately for any further signs or symptoms of decompression illness within the next 7 days. After suffering decompression sickness, you should not dive again until cleared by a doctor. Depending on the severity of symptoms, and if you have suffered decompression sickness before, your doctor will likely recommend not to dive again or to avoid diving for some amount of time.


Prevention

You can help prevent decompression illness and other types of barotrauma (decompression sickness) by following guidelines for diving taught in professional diving courses. The following actions increase your risk of developing decompression illness:

  • Diving outside dive table recommendations
  • Flying within 12-48 hours after diving: Most experts consider it reasonably safe to fly 12 hours after your last dive if you dove once, dove easily within the dive tables, and no decompression stop was required. For more complicated diving, waits of 24-48 hours have been recommended. In general, the longer you wait to fly after diving, the lower the risk of developing decompression sickness. Even long waits, however, do not reduce the risk all the way to zero.
  • Diving in cold water

  • Increased fat stores

  • Dehydration

  • Recent alcohol intoxication

  • Vigorous exertion while diving

  • Multiple repetitive dives

  • Jogging shortly after diving

  • Local physical injuries

Outlook

Prognosis varies with the following factors:

  • Prognosis is good with hyperbaric oxygen treatment.
  • Delay to hyperbaric oxygen treatment: Although reports show that victims can do well after days of symptoms, delay in definitive treatment may cause damage that is irreversible.
  • Severity of symptoms: Joint pains alone do better than focal weakness or inability to urinate.
Preexisting health: Young, healthy people can tolerate a greater insult to their health than an older person with other disease