title: Comparative open and closed valve nitrous analgesia study in humans.
mesh_terms: D000328:Adult; D000698:Analgesia / Q000379:methods*; D000769:Anesthesia, Inhalation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage*
chemical_list: D009609:Nitrous Oxide