US Patent 7140368 Laryngeal mask airway

A laryngeal mask airway has a main tubular shaft (1) with a mask portion (5) attached at its patient end (3). The mask portion (5) comprises a mount (50) and a sealing cuff (60) attached to the mount. The interior of the mount (50) defines a large volume atrium (54) communicating with the bore of the shaft (1) at one end and with an opening (61) through the cuff (60) at its other end. The join between the shaft (1) and the mount (50) is located above the rear part (63) of the cuff (60). The height of the atrium (54) is between 2.5 and 3.5 the internal diameter of the shaft. The volume of the atrium (54) is such that the ratio of the internal diameter of the shaft cubed to the internal volume of the atrium is between 50 and 68.