Nitrous oxide/oxygen analgesia in emergency care.

A method of analgesia relatively new to North American emergency care involves the use of a homogeneous gas composed of 50% nitrous oxide and 50% oxygen (Entonox). The gas is administered by the patient, who holds the Entonox apparatus mask to his face and triggers gas flow by exerting negative inspiratory pressure (-1 cm. H(2)O). Worthwhile analgesia (i.e. marked or partial pain relief) was achieved in 95% of 110 emergency department patients experiencing significant pain from various sources.