Patent ID: 8539953

Claim:
A surgical mask assembly for administering and scavenging medical gases, comprising: an outer shell having a first gas port configured to be coupled to a negative pressure source such that gas is exhausted from the outer shell to the negative pressure source through the first gas port, the outer shell defining a chamber with a rear-facing opening defined by a rim, the rim having an inner edge and an outer edge, and an inner shell having a second gas port that includes (i) a distal end configured to be coupled to a positive pressure source, and (ii) a proximal end that opens into the chamber of the inner shell such that gas from the positive pressure source is advanced through second gas port and out of the chamber of the inner shell to exit the inner shell, the inner shell defining a chamber with a rear-facing opening defined by a rim, the rim having an inner edge and an outer edge, wherein a superior-most point of the inner edge of the rim of the inner shell is positioned inferiorly and anteriorly relative to a superior-most point of the inner edge of the rim of the outer shell.