Nitrous oxide has a strong sedative and analgesic effect, but the anesthetic effect is weak, which has no irritation to respiratory tract and no damage to important organs of the body, and the patient is awake. Indications for inhaling nitrous oxide/oxygen are as follows: Scope of application Stomatology (endodontic treatment, periodontal treatment, oral implantation, etc. ) 1 patients with anxiety in stomatology need to calm down; 2. Patients with oral and pharyngeal sensitivity and nausea; ③ Patients who have difficulty in opening their mouth for a long time; Patients who hate sound and smell are related to dental treatment. Endoscopic application: gastroscope, enteroscope, ERCP, etc. Third, analgesia delivery. Four. induced abortion