Anesthesia ventilation system

In an anesthesia ventilator system wherein an inflatable bellows is enclosed in a sealed canister, with the interior of the bellows being in fluid communication with a patient breathing circuit and inflation and deflation of the bellows being controlled by a respirator in fluid communication with the portion of the interior of the canister surrounding the bellows, the respirator controlling inflation and deflation of the bellows by varying the pressure in the canister, the bellows being positioned for expansion in an upward direction during inflation, the improvement comprising:

• a rod extending upwardly from the top of the bellows;
• a sleeve mounted in the top of the canister and extending downwardly therefrom to a lower end, the sleeve having an elongated opening extending upwardly from the lower end, the opening being formed and positioned such that it mates with the rod on the bellows and constrains the rod to vertical movement as the bellows expands and contracts upwardly and downwardly, the sleeve including a valve actuating portion at the lower end;
• and
• valve means mounted in an opening in the upper surface of the bellows for permitting gas flow between the interior of the canister and the interior of the bellows, said valve means being resiliently biased in a normally closed position so as to block gas flow out of the bellows through said opening, the valve means being positioned for engagement with the valve actuating portion of the sleeve and being openable by engagement therewith after the bellows has expanded upwardly a predetermined distance, the opening of the valve means serving to relieve the internal gas pressure in the bellows.