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Subsections
Decompression Sickness

Wilderness Medicine

Decompression Sickness ("The Bends")

Background

  1. Definition
    • DCS is disease caused primarily by bubbles formed from dissolved gas in blood and/or tissue following a reduction in ambient pressure (most commonly diving)
    • Signs and symptoms are normally the result of air bubbles forming in joints and other tissues
      • Cause mechanical and biochemical effects
  2. Synopsis
    • Decompression Illness (DCI) is a more broad diagnosis that includes DCS and Arterial Gas Embolism (AGE)
    • Described for over 200 years
      • Initially in tunnel diggers-Caisson Disease
    • Common due to increase in recreational, no-decompression, SCUBA diving
    • Can also occur in aviators with accidental loss of cabin pressure at altitude and rapid re-pressurization or ascent to altitude in unpressurized cabin
      • Case reports from military aircraft

Pathophysiology

  1. Mechanism
    • Diver’s blood and tissues absorb additional gases from lungs at depth. If an ascent is too fast, this excess gas will separate from solution and form bubbles.
      • Primarily from nitrogen; Helium can also cause effects
      • Bubbles can produce mechanical, embolic, and biochemical effects
      • Bubbles in the tissues (autochthonous bubbles) can put pressure on nerves and tissues, leading to hemorrhage
      • Bubbles in veins and arteries (circulating bubbles) can cause obstruction or blood flow to tissues or embolism to lungs (from veins) or brain (from arteries).
  2. Etiology/Risk Factors
    • Gas burden (“depth and time”); not following dive tables
    • Multiple dives
    • Immersion in water
    • Environment: cold water and higher altitude for SCUBA
    • Obesity
    • Older (over 50)
    • Flying within 12 hours of diving
    • Exercise-at depth and after the dive
  3. Epidemiology
    • Incidence/Prevalence
      • Non-fatal DCS 0.01% (9.57/100,000 dives)
    • Morbidity/Mortality
      • 80% will have complete recovery
      • Even with severe DCS only 27% will have long term complications

Diagnostics

  1. History/Symptoms
    • See Diving history for more details
    • After surfacing, there is a latency period before symptoms appear
      • Several minutes to as long as several days (for most dives, onset of DCS can be expected within several hours of surfacing)
    • Detailed history of all dives/times, ascent rates, intervals between dives, breathing gases and complications with dive
    • Get detailed first aid information including all measures and their effect on symptoms
    • Record results of neuro exam done on site
    • Describe all joint or other musculoskeletal pain including: location, intensity and changes with movement/weight-bearing
    • Describe distribution of any rashes
    • Describe any traumatic injuries before, during and after dive
  2. Physical Exam/Signs
    • Still commonly divided into Type I and II
      • Type I: joint pain (musculoskeletal or pain-only symptoms) and cutaneous
      • Type II: Neurological, Inner ear, Cardiopulmonary
    • Thorough neurological exam is crucial for all DCS injuries
    • Pain: most common initial symptom and most common overall
      • 68% of cases
      • 58% joint pains (most common distribution in recreational SCUBA), 35% muscle pains, and 7% girdle pains
      • Joint crepitus/subcutaneous crepitus
    • Numbness/paresthesia’s
      • 63.4% of all cases
      • Can easily be missed if proper neurological exam not performed
    • Constitutional symptoms 48% of cases: headache, fatigue, malaise, nausea/vomiting, or anorexia
    • Cutaneous symptoms
      • 9.5% of cases
      • Pruritus or marbling
    • Neurological (Cerebral DCS)
      • Seizures, hemiplegia, diplopia, tunnel vision or scotomas, numbness, paresthesias, paralysis, mental status changes, decreased sensation to touch, muscle weakness,
      • Progress to AMS (altered mental status), coma or death
      • 18.7% of all cases have weakness
      • Less than 8% have other findings
      • 27% of CNS DCS will still be present at one month
    • Inner ear (“staggers”)
      • Vertigo, nausea, vomiting, deafness, tinnitus, and nystagmus
      • Immediate treatment important due to small vasculature
    • Cardiopulmonary (“chokes”)
      • Massive blocking of pulmonary circulation by bubbles
      • Substernal pain, cough,and dyspnea
      • Usually occurs within minutes
      • 5.6% of cases
      • Can lead to respiratory failure and shock if not treated immediately
    • Other less common symptoms include bladder, bowel, GI and cardiovascular symptoms
  3. Labs/Tests
    • Diagnosis is clinical – do not rely on imaging or laboratory data
    • Laboratory evaluation by recommendation of Undersea and Hyperbaric Medicine Society (UHMS)
      • CBC: evaluate for DIC
      • BMP: evaluate for hypoglycemia
      • Toxicology screen: evaluate for other causes
      • CPK: some evidence shows AGE elevated vs. normal in DCS
  4. Imaging
    • Plain film imaging: evaluate for gas
    • Electronystagmography: decide inner ear DCS vs. barotrauma
  5. Other Tests/Criteria
    • Neuropsychiatric testing for evaluation of subtle CNS findings
    • SANDHOG and RNZN
      • Two clinical scales previously studied to help diagnose DCS
      • Limited clinical usefulness
  6. Differential Diagnosis
    • Arterial Gas Embolism
      • Type II DCS may have similar presentation as AGE
        • AGE usually occurs within 10 minutes of surfacing
      • Initial treatment is the same (do not delay in order to make diagnosis)
    • Inner ear barotrauma
    • Middle ear/maxillary sinus over-inflation
    • Contaminated diving gas
    • Oxygen toxicity-especially with use of Nitrox
    • Musculoskeletal strains
    • Seafood toxin ingestion
    • Immersion pulmonary edema
    • Water aspiration

Treatment

  1. Initial/Prep/Goals (see also Divers' Alert Network )
    • Surface Oxygen 100% NRB facemask
      • Do not use ENTOX (50% O2 50% N2) as this can exacerbate pneumothorax
      • In-water recompression should only be done in remote areas
    • US Navy (USN) and UHMS guidelines support recompression then controlled decompression following USN Dive Table 6
    • Contact Diver’s Alert Network (DAN): (919) 684-9111
    • May require intubation and aggressive resuscitation (e.g., ACLS, ATLS)
    • In-water recompression should only be done in remote areas
  2. Medical/Pharmaceutical
    • NSAIDs
      • Shows conflicting evidence
    • IV fluids: bolus of NS or LR
      • Until urinary output is 1-2 mL/kg/hr
  3. Continued Management (24 hrs)
    • May require repeat chamber trips
    • Use LWMH for those with leg immobility
    • Conflicting data for IV lidocaine as adjunct to HBOT
    • Do not use steroids
    • Transport via ground if possible
      • Aircraft maintain maximum cabin altitude of 1000 ft above sea level
  4. Prevention
    • All divers should have pre-dive medical clearance
    • Safety stops (3-5 minutes at 10-20 feet)
    • Ascend slowly (< 30 ft/min)
    • Use a dive computer/dive table
    • Plan dive carefully
    • Keep fit, well hydrated and avoid alcohol
    • No flying until 12 hours after a single dive
    • No flying until 18 hours after a series of multiple dives

Disposition

  1. Admission Criteria
    • Admit all
  2. Consult(s)
    • All patients should be transferred to facilities with hyperbaric oxygen chamber
  3. Discharge/Follow-Up instructions
    • With mild and moderate DCS divers normally can return to sport in 4 weeks
    • Severe DCS, with cerebral DCS or continued symptoms, should not return to diving until cleared by a Diving Medical Specialist

References

  1. Bennett, Michael, Carl Edmonds, John Lippmann, and Simon Mitchell. Diving and Subaquatic Medicine. 2016.
  2. Arthur DC, Margulies RA. A short course in diving medicine. Ann Emerg Med. Jun 1987;16(6):689-701
  3. Vann RD, Butler FK, Mitchell SJ, Moon RE. Decompression illness. Lancet. Jan 8, 2011;377(9760):153-164
  4. Bason R, Yacavone D, Bellenkes AH. Decompression sickness: USN operational experience 1969-1989. Aviat Space Environ Med. Oct 1991;62(10):994-996
  5. Ladd G, Stepan, V, Stevens, L. The Abacus Project: establishing the risk of recreational scuba death and decompression illness. South Pacific Underwater Medicine Society (SPUMS) Journal. 2002;32(3):124-128
  6. Dujic Z, Valic Z, Brubakk AO. Beneficial role of exercise on scuba diving. Exerc Sport Sci Rev. Jan 2008;36(1):38-42
  7. Moon RE, Sheffield PJ. Guidelines for treatment of DCS. Aviat Space Environ Med. 1997;68:234-243
  8. Holley T. Validation of the RNZN system for scoring severity and measuring recovery in decompression illness. South Pacific Underwater Medicine Society (SPUMS) Journal. 2000;30(2):75-80
  9. Grover I, Reed W, Neuman T. The SANDHOG criteria and its validation for the diagnosis of DCS arising from bounce diving. Undersea Hyperb Med. May-Jun 2007;34(3):199-210
  10. UHMS Adjunctive Therapy ad hoc subcommittee. Adjunctive therapy for decompression illness (DCI): Summary of Undersea and Hyperbaric Medical Society guidelines 2002. Available at: https://www.uhms.org/images/Position-Statements/adjunctive_committee_summary.pdf. [Accessed December 2021]
  11. Mitchell SJ, Doolette DJ. Management of Mild or Marginal Decompression Illness in Remote Locations Workshop Proceedings. 2004. Available at: https://www.diversalertnetwork.org/files/RemoteWrkshpFinal05.pdf. [Accessed December 2016]
    MacDonald RD, O'Donnell C, Allan GM, et al. Interfacility transport of patients with decompression illness: literature review and consensus statement. Prehosp Emerg Care. Oct-Dec 2006;10(4):482-487

Contributor(s)

  1. Ho, Nghia, MD
  2. Ward, Toussaint, MD, MHA
  3. Christopher Androski, MD
  4. Aaron Yallowitz, MD
  5. Eric Koch, DO, FAWM

Updated/Reviewed: December 2021