Decompression Sickness

OVERVIEW

Decompression sickness, is a form of decompression illness, where a reduction in ambient pressure (‘decompression’) leads to de no intravascular and extravascular bubble formation with pathological consequences

• decompression sickness = ‘small bubbles’
• arterial gas embolism (AGE) is the other form of decompression illness, characterised by ‘big bubbles’ that are introduced into the circulation following alveolar rupture during decompression

• the altitude threshold for DCS is generally 18,000 ft
• most diving is done @ 2-4 atmospheres

PATHOPHYSIOLOGY

Typically affects

• divers
• caisson workers
• aviators
• astronauts

Mechanism

1. release of bubbles of inert gas into the blood and tissues with mechanical, embolic and biochemical effects
2. hypoxia induced vasoconstriction -> increased pulmonary capillary pressure, alveolar fluid transudation, decreased alveolar fluid clearance
3. endothelial activation -> capillary leak
4. increased leukocyte adhesion, inflammatory response and reperfusion injury
5. vessel obstruction
6. tissue distortion causing pain
7. embolisation (25% of people have PFO so can embolise to the brain)

CLINICAL FEATURES

• cough -> respiratory failure

Type I Decompression Sickness

• musculoskeletal pain (limbs, shoulders, elbows, hips, knees)
• anorexia
• malaise
• fatigue
• orange appearance of skin from local lymphatic obstruction
• pruritis (ears, trunk, wrists, hands -> trunk)
• cyanosis

Type II Decompression Sickness

• substernal discomfort
• pleuritic chest pain
• tachypnoea
• non-productive cough
• right heart strain
• cardiovascular collapse
• paraesthesia
• full paralysis
• convulsions
• cerebellar signs

MANAGEMENT

Prevention

• no flying for 24 hours after a dive

Proven Benefit

• FiO2 1.0 (enhanced de-nitrogenation)
• CPR
• isotonic fluid resuscitation — dehydration due to capillary leak, cold diuresis and immersion diuresis
• hyperbaric therapy (even very late) — 2-3 atm, repeated until no further benefil
• intubate and fill cuff with saline

Unproven Benefit

• Trendelenburg position (not longer than 30min c/o cerebral oedema)
• avoid glucose IV
• avoid hypertension and anxiety
• corticosteroids
• benzodiazepine for seizures
• aspirin

Questionable Benefit

• Ca2+ blockers
• lignocaine 1mg/kg
• NSAIDS, heparin, prostaglandin
• induced hypothermia
• cerebral venoarterial perfusion

Proven Detrimental

• recompression while submerged
• alcohol
• analgesics
• delayed transport to hyperbaric center
• additional hypobaric exposures

Transfer by helicopter at 300m, on land or pressurize to sea-level

References and Links

• Bennett MH, Lehm JP, Mitchell SJ, Wasiak J. Recompression and adjunctive therapy for decompression illness. Cochrane Database Syst Rev. 2012 May 16;5:CD005277. PMID: 22592704.
• Lynch JH, Bove AA. Diving medicine: a review of current evidence. J Spec Oper Med. 2009 Fall;9(4):72-9. PMID: 20112651.
• McMullin AM. Scuba diving: What you and your patients need to know. Cleve Clin J Med. 2006 Aug;73(8):711-2, 714, 716 passim. PMID: 16913196.
• Sebel PS. 20,000 leagues under the sea. Anesth Analg. 2010 Sep;111(3):589-90. doi: 10.1213/ANE.0b013e3181eb64de. PubMed PMID: 20733161.
• Tetzlaff K, Shank ES, Muth CM. Evaluation and management of decompression illness–an intensivist’s perspective. Intensive Care Med. 2003 Dec;29(12):2128-36. PMID: 14600806.
• Vann RD, Butler FK, Mitchell SJ, Moon RE. Decompression illness. Lancet. 2011 Jan 8;377(9760):153-64. doi: 10.1016/S0140-6736(10)61085-9. Review. PubMed PMID: 21215883.