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

release of bubbles of inert gas into the blood and tissues with mechanical, embolic and biochemical effects
hypoxia induced vasoconstriction -> increased pulmonary capillary pressure, alveolar fluid transudation, decreased alveolar fluid clearance
endothelial activation -> capillary leak
increased leukocyte adhesion, inflammatory response and reperfusion injury
vessel obstruction
tissue distortion causing pain
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.