Causes of hypoventilation
■ Tongue (falling back) or laryngeal spasm
■ Foreign bodies (e.g. tooth, gauze), secretions, blood (due to trauma), vomit (including
particulate matter), tumours
■ Oedema or haematoma following surgery (particularly surgery involving the airway, e.g.
ear, nose and throat (ENT), thyroid surgery).
Central respiratory depression
■ Residual inhalational or intravenous anaesthetic agents
■ Strong analgesics, particularly opioids (e.g. morphine)
■ Intracranial event (e.g. stroke).
Impaired mechanics of breathing
■ Pain (particularly after abdominal surgery), leading to splinting of the diaphragm
■ Residual effects of muscle relaxants
■ Pneumothorax, haemothorax
■ Obesity, leading to splinting of the diaphragm.