 - contraindication to morphine administration hypersensitivity to morphine, decompensate respiratory failure, acute head trauma, uncontrolled epilepsy, severe hepatocellular failure, intracranial hypertension, use of buprenorphine or nalbuphine Contraindications to MEOPA administration, intra-cranial hypertension, non cooperative patient sleepiness; encephalopathy, refusal to participate, pneumothorax, emphysema, pneumoperitoneum, digestive occlusion, pneumomediastinum, air embolism, diving accident , facial trauma, patients who recent administration of an ophthalmic gas SF6, C3F8, C2F6 3 months. 