Decompression illness (DCI)
Decompression illness (DCI) is the umbrella term for the acute clinical syndromes caused by inert‑gas bubbles forming in tissues or the circulation as ambient pressure falls. It includes:
- Decompression sickness (DCS): in‑situ tissue or venous bubble formation after inadequate decompression.
- Arterial gas embolism (AGE): arterialisation of gas bubbles due to pulmonary barotrauma (alveolar rupture) or paradoxical embolism via a right‑to‑left shunt (e.g. patent foramen ovale, PFO).
DCI is a core emergency‑medicine topic (RCEM curriculum). Early recognition, immediate supportive care and prompt liaison with hyperbaric services markedly affect outcome.
Pathophysiology and risk factors
Breathing compressed gas at depth increases dissolved inert gas (mainly nitrogen) in tissues (Henry’s law). Rapid ascent or inadequate decompression causes supersaturation and bubble formation. Bubbles injure by mechanical distortion, vascular obstruction, endothelial dysfunction, inflammation and coagulation activation.
AGE may arise from alveolar rupture during ascent (breath‑holding, airway obstruction, positive‑pressure ventilation, underlying lung disease) or from venous bubbles bypassing the pulmonary filter via a PFO or pulmonary AV shunt.
Recognised risk factors
- Rapid ascent, omitted or inadequate decompression stops, repetitive dives with short surface intervals, deep or prolonged dives
- Heavy exercise around the time of ascent, dehydration, cold, obesity
- Pulmonary disease or breath‑holding on ascent
- Equipment failure (faulty dive computer) - check and document device details; report suspected failures via product‑safety pathways (GOV.UK)