Caisson Disease Decompression sickness (The Bends)
Related Subjects:
|Assessing Breathlessness
|Respiratory failure
|Caisson Disease - Decompression sickness
|Altitude sickness / Acute Mountain sickness
⚓ Caissons were watertight structures used in 19th-century bridge and harbour building. Workers inside were exposed to high pressure below sea level. Rapid ascent caused "Caisson disease" (now known as decompression sickness).
🌊 About
- Also called Decompression sickness (DCS), Divers’ disease, or the Bends.
- Caused by inert gas (mainly nitrogen) coming out of solution when moving from high → low pressure.
- Bubble formation in blood and tissues leads to mechanical obstruction and inflammatory injury.
⚠️ Aetiology
- Transition from high-pressure breathing (diving, caisson, hyperbaric work) to normal/low pressure.
- Nitrogen or helium bubbles lodge in tissues and vessels → ischaemia & infarction.
- Bubbles can also trigger platelet activation and endothelial damage, compounding injury.
↕️ Situations of Risk
- Scuba diving surfacing too quickly 🐠
- Unpressurised aircraft at high altitude ✈️
- Spacewalk from spacecraft 🚀
- Deep mine or caisson work ⛏️
- Multiple exposures (e.g. diving then flying the same day)
- Cabin pressure failure in flight
- Diving at altitude (lower ambient pressure = higher risk)
🧩 Other Risk Factors
- Magnitude of pressure change (deeper = riskier)
- Rate of ascent (fast = worse)
- Duration of exposure
- Dehydration, obesity
- PFO (patent foramen ovale) ➝ increases risk of systemic emboli (stroke, cord injury)
🛡️ Prevention
- Pre-breathing 100% oxygen to "wash out" nitrogen
- Ascent rate < 10 metres/minute
- Staged decompression stops 🕑
- Use of decompression tables or dive computers
🩺 Clinical Features
- MSK/skin: joint pains ("the bends"), itching, mottling, formication
- Neurology: dizziness, visual changes, mood changes, weakness, seizures, coma
- Cardiorespiratory: cough, dyspnoea, chest pain ("the chokes")
- ⏱️ Most present within 48h of exposure
🔎 Investigations
- Routine bloods: FBC, U&E, LFTs, ABG, lactate
- MRI: lesions in white matter tracts, especially thoracic spinal cord → bubbles accumulate in fat-rich myelinated areas with lower perfusion
💊 Management
- Immediate 100% oxygen (accelerates nitrogen washout)
- IV fluids, analgesia
- Definitive: Hyperbaric oxygen in a recompression chamber 🌡️
📚 References
- Bennett & Elliott’s Physiology and Medicine of Diving
- UHMS Guidelines on Decompression Illness
