The Effect of Entonox on Labour Pain Relief among Nulliparous Women: A Randomized Controlled Trial

Labour pain is one of the most severe pain in humans. Fear of labour pain is the most dreadful reason for Caesarean Section (CS). Entonox (a mixture of nitrous oxide+oxygen) is a safe inhalational analgesia during labour pain.

This study investigated the effect of entonox on pain relief and length of labour in nulliparous women.

A clinical trial study was conducted among 120 nulliparous women (60 in intervention and 60 in control group) in 2015 in Atieh Hospital, Hamadan city, Iran. The women were chosen randomly to receive either entonox in the intervention group or oxygen in the control group. For the intervention group, entonox inhalation was introduced at the initiation of pain at each contraction. entonox gas was administrated via a face-mask. This enabled the women to breathe fresh gas in each inspiration. In the control group the oxygen inhalation was given with occurrence of pain at each contraction too. In both groups, the gas administration continued until the end of contraction pain with the patient finally breathing room air. Pain using Visual Analogue Scale (VAS), duration of labour and side effects were compared in two groups.

The mean age of women was 25.69 (SD=4.83). There were significant differences between two groups on labour pain at the first, second, third and fourth hours after intervention (p<0.05). Duration of labour in the intervention group (64.80 minutes) was significantly shorter than the control group (98.33 minutes) (p<0.05). There were no significant differences between the two groups on women's blood pressure and neonatal Apgar score. Only dizziness was slightly higher in the intervention group compared to the control group (p<0.05).

Entonox provides significant pain relief and it can quickly be implemented during painful labour.