Abstract: An anesthesia system wherein the respiratory system is fitted with interchangeable patient circuit modules that allows a generic fitting in the machine to have affixed, hereto, a module that has ports suitable for connection to various patient breathing circuits. As such, the anesthesia machine can have the patient circuit modules easily changed and thus be adaptable for use with patient breathing circuits such as the circle system, the open/nonrebreathing circuit and the Bain or Mapleson D circuits. A detector system is provided that identifies that particular patient module installed in the anesthesia machine to alert the main CPU and to thus provide the correct flow sensing schemes and flows to the patient breathing circuit then being used.

Abstract: An adjustable pressure limiting valve having a non-linear biasing means. The valve has a movable valve member that can be moved to an open position by a predetermined pressure and a closed position on a valve seat. A rotating control knob is rotated by the user to adjust the bias acting against the movable valve member toward the closed position to, in turn, set the pressure at which the valve opens. A rotating cylindrical drum rotates along with the control knob and has a helical groove formed in its exterior and a pair of fixed pins that ride in the helical groove. When the cylindrical drum is rotated, the fixed pins riding in the helical grove cause the cylindrical drum to move along its longitudinal axis to compress or decompress a spring acting against the movable valve member. The pitch of the helical groove is designed so as to create a non-linear relationship between the rotational movement of the control knob and the longitudinal movement of the cylindrical drum.