A mask for relative analgesia and anaesthesia is moulded from polymeric foam and fits over the nose of the patient, with lateral ports for inlet and outlet of gases. The periphery of the mask has a lower region which bears upon the base of the upper lip, an upper region which contacts the nasal bones,...http://www.google.es/patents/US4803981?utm_source=gb-gplus-sharePatente US4803981 - Anaesthesia mask
