Patients is not breathing after anaesthesia is due to

(All of the above) (513 - Lees 13th)* Hypoxaemia is best detected by a pulse oximeter or measurement of blood gases. Hypoxaemia is a late sign of hypoventilationApnoea during spinal and extra dural anaesthesiaCauses of apnoea during spinal and extradural analgesia include* Inadeguate medullary blood flow due to inadequate cardiac output - a serious situation demanding immediate cardio respiratory support* Total spinal analgesia with denervation of all the respiratory muscles true phrenic paralysis is uncommon because the motor roots are large* Accidental subdural injection : a small volume of solution may travel to an unexpectedly high level in this potential space* Toxic effects of the local analgesic drug* Injection of a opioid analgesic drug