Laryngeal incompetence during experimental "relative analgesia" using 50% nitrous oxide in oxygen. A preliminary report.
Ten healthy adult volunteers inhaled 50% nitrous oxide in oxygen while dental treatment was simulated for a period of 30 min. During this time 15 ml of radio-opaque dye was placed at the back of the tongue. A similar control study was performed 1 week later, the subjects inhaling pure oxygen without nitrous oxide. X-ray examination revealed that two of the 10 volunteers had aspirated dye while breathing nitrous oxide and oxygen, but no aspiration was apparent in the control study.