When scuba diving, additional oxygen and nitrogen dissolve in body tissues.  The additional oxygen is consumed by the tissues, but the excess nitrogen must be washed out by the blood during decompression.  During or after ascent this excess nitrogen gas can form bubbles in the tissues, analogous to the carbon dioxide bubbles that form when a carbonated beverage container is opened.  These bubbles may then cause symptoms that are referred to as decompression sickness (“DCS” or “the bends”).  Trapping of gas within the lungs during ascent, either because the lung is diseased or because of breath-holding, can cause bubbles to be forced into the bloodstream (“arterial gas embolism” or “AGE”), where they can block the flow of blood or damage the lining of blood vessels supplying critical organs such as the brain.  AGE can also occur in non-divers, due to entry of air into the body, such as during medical diagnostic or therapeutic procedures.  Symptoms of DCS or AGE can include joint pain, numbness, tingling, skin rash, extreme fatigue, weakness of arms or legs, dizziness, loss of hearing, and in serious cases, complete paralysis or unconsciousness.

Emergency treatment of DCS or AGE includes administration of oxygen and measures to maintain adequate blood pressure, such as lying the patient down and fluid (either oral or intravenous, depending upon availability and severity of the illness).  Definitive treatment for DCS or AGE is administration of 100% oxygen at increased atmospheric pressure in a hyperbaric chamber (typically at a pressure 2-3 times greater than normal atmospheric pressure).

While some delay in transporting a patient to a hyperbaric chamber is usually unavoidable, the success in relieving symptoms is greater if the treatment is administered within a few hours after the onset of symptoms.  Some improvement might be expected, particularly in mild cases, even after a day or more of delay.

The vast majority of cases respond satisfactorily to a single hyperbaric oxygen treatment.  Sometimes, repetitive treatments are recommended until no further improvement can be observed.  A small minority of divers with severe neurological injury may require 15-20 repetitive treatments.  The success of hyperbaric oxygen treatment for
DCS or AGE has borne the test of time, and continues to be the standard of care for the treatment of these disorders.


1.        Francis TJR, Gorman DF.  Pathogenesis of the decompression disorders.  In: Bennett PB, Elliott DH, eds.  The Physiology and Medicine of Diving.  Philadelphia: W.B. Saunders, 1993:454-480.

2.        Elliott DH, Moon RE.  Manifestations of the decompression disorders.  In: Bennett PB, Elliott DH, eds.  The Physiology and Medicine of Diving.  Philadelphia, PA: WB Saunders, 1993:481-505.

3.        Moon RE, Sheffield PJ.  Guidelines for treatment of decompression illness.  Aviat Space Environ Med 1997;68:234-243.

4.        Navy Department.  US Navy Diving Manual.  Vol 1 Revision 3:  Air Diving.  NAVSEA 0994-LP-001-9110.  Flagstaff, AZ:  Best, 1993.

5.        Ball R.  Effect of severity, time to recompression with oxygen, and retreatment on outcome in forty-nine cases of spinal cord decompression sickness.  Undersea Hyperbaric Med 1993;20:133-145.

6.        Kizer KW.  Delayed treatment of dysbarism: a retrospective review of 50 cases.  JAMA 1982;247:2555-8.

7.        Moon RE, Gorman D:  Treatment of the Decompression Disorders.  In:  The Physiology and Medicine of Diving.  Edited by Bennett PB, Elliott DH.  Philadelphia, PA, Saunders, 1993, pp 506-541.



Other references on Decompression Sickness:





In the context of the Medicare 35-10 document, this "Covered Condition" refers to Decompression Sickness. Modern (post-1995) terminology defines Decom-pression Illness as the syndrome of gas-induced disease that encompasses both Gas Embolism and Decompression Sickness. This evolution is, in part, the result of the frequent difficulty in distinguishing these conditions when they involve a barotraumatic etiology.

  • Anon: U.S. Navy Diving Manual, Volume 1 (Air Diving) 1993; Revision 3:8-22--8-28. Best Publishing Company, Flagstaff, Arizona.
    The authoritative text of the
    United States military government. It states, among other things, that "Any decompression sickness that occurs must be treated with recompression (hyperbaric oxygen therapy)".
  • Anon: NOAA Diviing Manual, Diving for Science and Technology 1991;20-8--20-9.
    The authoritative text of the
    United States civilian government. It states, among other things, "The only adequate treatment for … gas embolism in divers is recompression in a recompression (hyperbaric) chamber".
  • Rudge FW, Shafer, MR: The effect of delay on treatment outcome in altitude-induced decompression sickness. Aviat. Space Environ. Med. 1991;62:687-690.
    A military government review of 232 cases of decompression sickness. The success of treatment was inversely related to delay in treatment. Stated differently, closure or non-availability of local and regional hyperbaric treatment facilities is likely to result in career/occupatiol ending sequelae, with the not insignificant longitudinal health costs associated with rehabilitation and supportive care.
  • Melamed Y, Shupak A, Bitterman H: Medical problems associated with underwater diving. The New England Journal of Medicine 1992;326(1):30-35.
    A comprehensive review article. It identifies a critical diagnostic issue in that subtle neurological injury may co-exist with less severe musculoskeletal involvement. Non-diving/hyperbaric specialists may well miss this point, resulting in inappropriate treatment, and long term (and costly)morbidity.
  • Hallenbeck JM, Bove AA, Elliott DH: Mechanisms underlying spinal cord damage in decompression sickness. Neurology 1975;25:308-316
    A fundamental determination of the evolution of decompression sickness, demonstrating obstruction and ischemia of the spinal cord venous drainage, resulting in infarction. No intervention other than hyperbaric oxygenation has been tried or proposed as therapeutically appropriate and able to reverse this process. Pharmacologic adjuncts are actively under investigation. However, the fundamental issue is reduction/elimination of gaseous emboli. Hyperbaric pressurization must, therefore, be considered mandatory.
  • VanDerAue OE, Duffner GJ, Behnke AR: The treatment of decompression sickness: an analysis of one hundred and thirteen cases. The Journal of Industrial Hygiene and Toxicology 1947;29(6):359-366.
    An historically important paper. It describes, in a large clinical series, the effectiveness of hyperbaric therapy in the successful resolution of wide-ranging presentations, involving both the nervous and musculoskeletal systems.
  • Millington T: "No tech" technical diving: the lobster divers of La Mosquitia. SPUMS Journal 1997;27(3):147-148.
    An example of the resulting human toll when decompression sickness sufferers do not undergo hyperbaric oxygen therapy. "Inundated with paralyzed divers".
  • Green JW, Tichenor J, Curley MD: Treatment of type I decompression sickness using the U.S. Navy treatment algorithm. Undersea Biomed Res 1989;16(6):465-470.
    A 20-year review of central nervous system decompression sickness. "Inappropriate practices such as ….Non-treatment … resulted in a high incidence of deterioration or relapse".
  • Rivera JC: Decompression sickness among divers: an analysis of 935 cases. Military Medicine 1964:314-334.
    The U. S. Navy’s experience, involving almost 1,000 cases. It, again, demonstrates the efficacy of immediate hyperbaric treatment.
  • Moon RE: Treatment of gas bubble disease. Problems in Respiratory Care 1991;4(2):232-252.
    Comprehensive review article.
  • Moon RE, Sheffield PJ: Guidelines for treatment of decompression illness. Aviation, Space, and Environmental Medicine 1997;68(3):234-243.
    Consensus statement/guidelines for the treatment of decompression sickness, based upon a scientific workshop involving an internationally-respected faculty. "Definitive treatment … incorporates compression and administration of breathing gas with elevated partial pressures of oxygen". "Rapid administration of pressure and oxygen is paramount …"