Efficacy of Premixed Nitrous Oxide and Oxygen in Patient With Out-of-hospital Moderate Acute Pain: a Randomized Double-blind Study

The study will evaluate the efficacy of premixed nitrous oxide and oxygen (MEOPA) in patients with out-of-hospital moderate acute pain.

The primary endpoint is the percentage of patients with pain relief (with a numerical rating scale of 3/10 or lower) 15 minutes after randomisation. Secondary endpoints are treatment safety and adverse events, time to analgesia and duration of analgesia. This study will expect 60 patients assigned in two parallel groups, defined by a randomization scheme. Group assignments were sealed in opaque envelopes and will be open sequentially by the dispatcher when the paramedic is ready to include the patient. The letter contained in the envelope corresponds to the cylinder to use. Eligible patients with a numeric rating scale (NRS) score between 3 and 6/10 are randomly allocated to receive either MEOPA, or medical air. Fifteen minutes after the randomisation, all patients will receive MEOPA from a distinct cylinder. Pain score will be measured at baseline and every 5 minutes until pain relief will be obtained. The paramedic blinded to the analgesic treatment groups will do all assessments of patients. The safety evaluation will include non invasive monitoring of blood pressure, heart rate, oxygen saturation by pulse oximetry (SpO2) and adverse events collection.