Pulse oximetry is widely used during anaesthetic practice to monitor heart rate and oxygenation and has been recommended as a monitor when sedative techniques are used. We monitored 25 patients receiving sedation for chemonucleolysis and showed that 17 became hypoxaemic at some stage of the procedure, none of whom had clinically detectable signs of respiratory depression. We recommend that monitoring with pulse oximetry is used in all patients receiving sedation for radiological procedures and that all radiologists administering sedation be trained in airway management.