Patent ID: 8011363

Claim:
An exhalation valve for use in an underwater breathing device, the exhalation valve configured to produce positive end-expiratory pressure in the airway of a user of the underwater breathing device in order to reduce the overall work of underwater breathing, the exhalation valve comprising: a valve plate defining at least one chamber port and an exhalation port, the at least one chamber port being positioned opposite the exhalation port; and a flexible membrane that is sealable against a surface of the valve plate and is sized and positioned to be capable of sealing the exhalation port, the flexible membrane comprising: a sealed position in which the flexible membrane seals the exhalation port such that substantially no air can flow between the at least one chamber port and the exhalation port; and an unsealed position in which the flexible membrane does not seal the exhalation port such that air can flow between the at least one chamber port and the exhalation port; wherein the valve plate is substantially rigid and substantially disk-shaped.