Inhaled patient-administered nitrous oxide/oxygen mixture does not impair driving ability when used as analgesia during screening flexible sigmoidoscopy

Background: Entonox (nitrous oxide/oxygen mixture) has an analgesic effect, but its use is currently contraindicated in patients who plan to drive after its administration. We assessed the effect on driving ability of Entonox used as analgesia in patients undergoing screening flexible sigmoidoscopy. Methods: Forty men and 40 women scheduled for screening flexible sigmoidoscopy who had not driven to the examination site were recruited together with a matched control subject from the same list. Before the examination complex motor skills were assessed in both groups using an adaptive tracking task, previously demonstrated to be the most sensitive test for detecting impairment of driving ability due to drugs. During the examination Entonox analgesia was available to the study group only, and after the screening examination complex motor function was retested on the same computer. Results: Both groups improved their computer score on repeat testing, by 0.53 (range -1.9 to 4.6) in the study group and by 0.44 (range -0.6 to 2.5) in the control group. Conclusions: These data strongly support the view that Entonox analgesia does not impair driving ability. In the context of screening flexible sigmoidoscopy its use may lead to an increase in compliance.