Decompression sickness


  • Also known as "the bends"
  • Dissolved nitrogen (and occasionally helium) comes out of solution and forms bubbles in blood and tissue
  • Occurs in rapid ascent in diving, and more rarely in military operations rapid ascent in high altitude aviation or hypobarics training

Diving Physiology

  • Pascals Law applies to the diving body (without air filled areas such as lungs) states that the pressure applied to any part of the enclosed liquid will be transmitted equally in all directions through the liquid.
  • Boyles Law applies to the diving body's air filled areas such as lungs, sinuses, middle ear, and states that the volume and pressure of a gas at a given temperature are inversely related.
    • At 2 ATA (10m/33ft) a given gas would be 1/2 it's volume, at 3 ATA (20m/66ft) it would be 1/3 it's volume and so on.
Boyle's Law

Clinical Features

  • Symptom typically start soon after surfacing
    • 42% in 1 hr, 60% in 3 hr, and 98% in 24 hr[1]
    • CNS cases present more rapidly – 56% within 10 mins[2]
    • Some symptoms can be delayed for days[3]

Type I (Pain only DCS)

  • Involves the joints and extremities, with constitutional symptoms
  • Usually only single joint is involved, most commonly:
    • Shoulder
    • Elbow
    • Knee
  • Skin and lymphatics
    • Pruritus, stinging, paresthesias, hot/cold sensations
    • Fine scarletiniform rash from nitrogen movement through sweat glands
    • Cutis marmorata - marbling rash, purplish-bluish discoloration, otherwise common and normal in infants
    • Pitting edema, peripheral swelling from lymphatic blockage

Type II (Serious DCS)

  • Some consider multiple joint involvement qualifies as Type II
  • Spinal cord involvement
    • Ascending paralysis
    • Signs often cannot be traced to single location in the cord (may have skip lesions)
  • Vestibular ("staggers") involvement
  • Pulmonary "chokes"

Type III (Type II + gas embolism)

  • Variety of stroke symptoms/signs
    • May spontaneously resolve

Differential Diagnosis

Diving Emergencies


Decompression sickness is a clinical diagnosis

  • Pain may be reduced by BP cuff inflation over the joint to 150-200 mmHg
  • In patients that are ambiguous or decompensated, consider additional workup without delaying definitive treatment
  • Other considerations
    • Fingerstick
    • CBC
    • Chem10
    • Lactate
    • PT/PTT
    • VBG (or ABG)
    • Ethanol level
    • Consider UDT


Treatment based almost solely on case reports and series

  • Denitrogenation with 100% NRB regardless of SpO2, and continue 2 hours after symptom resolution
  • Keep supine, Trendelenburg not recommended[4]
  • Initiate IV crystalloid fluids, rate of 250 cc/hr for first few hours
  • Hyperbaric oxygen
    • Effective even in delayed cases
    • Immediate recompression for suspicion of Type 2 DCS, in consultation with hyperbarics specialist
    • Do not wait for recompression, but if delayed presentation, may recompress up to 14 days after symptom onset[5][6]
  • If due to high altitude aviation or hypobarics
    • Descend to ground level ASAP
  • Contact Divers Alert Network (DAN) Emergency Hotline at 1-919-684-2948[7]
    • Similar function as to poison control
  • If patient requires transport to another facility, consider ground transport, air transport at max of 1000 ft, or air transport with pressurization capability
    • O2 with tight fitting mask during flight
  • Consider adjuncts such as Lidocaine, Perfluorocarbon emulsions


  • Hyperbaric chamber and admission


  • One study showed at an average of 6.1 yrs, almost 50% of patients had impairments[8]
    • These include impaired urination, defication, and sexual function

See Also

External Links


  1. Navy Department. US Navy Diving Manual. Revision 6. Vol 5: Diving Medicine and Recompression Chamber Operations. NAVSEA 0910-LP-106-0957. Washington, DC: Naval Sea Systems Command, 2008.
  2. Francis TJ, et al. Central nervous system decompression sickness: latency of 1070 human cases. Undersea Biomed Res. 1988; 15:403–417.
  3. Freiberger JJ, et al. The relative risk of decompression sickness during and after air travel following diving. Aviat Space Environ Med. 2002; 73:980–984.
  4. Moon RE, ry sl. Guidelines for treatment of decompression illness. Aviat Space Environ Med. 1997; 68:234–243.
  5. Marx et al. Rosen's Emergency Medicine - Concepts and Clinical Practice. 8th Ed. 2013. Ch 143. Pg. 1925.
  6. Edmonds C et al. Diving and Subaquatic Medicine, Fifth Edition. 2015. Decompression Sickness: Treatments. Pg 173.
  7. Accessed 11/15/2018
  8. Vann RD, et al. Decompression illness. Lancet. 2011; 377(9760):153-164.