Acceptability of continuous nasal nitrous oxide during labour--a field trial in six maternity hospitals.

In six maternity hospital 516 mothers during labour received 50% nitrous oxide and 50% oxygen (Entonox) continuously at 5 litres/minute through a single-end nasal catheter and intermittently by a mouthpiece for a mean duration of 3 hours 30 minutes (513 mothers). A comparison was made with a control group of 575 mothers who had intermittent inhalation of Entonox only for a mean duration of 3 hours 6 minutes (574 mothers). The midwives had no difficulty learning to manage the administration of nasal Entonox. Eighty-six per cent of mothers agreed to use the nasal method and 70% continued for the duration of their labour. The midwives reported that pain relief was improved, and 51 (92%) would wish to continue offering the technique.