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Correspondence  |   February 2007
Malfunction of the New Aisys® Anesthesia Machine
Author Affiliations & Notes
  • David Wax, M.D.
    *
  • *Mount Sinai School of Medicine, New York, New York.
Article Information
Correspondence
Correspondence   |   February 2007
Malfunction of the New Aisys® Anesthesia Machine
Anesthesiology 2 2007, Vol.106, 404-405. doi:
Anesthesiology 2 2007, Vol.106, 404-405. doi:
To the Editor:—
We recently replaced most of our anesthesia machine fleet with the newly available Aisys® Carestation (GE Healthcare, Waukesha, WI). In the course of using these second-generation electronic machines, we have encountered two clinically significant problems that have each occurred on more than one unit.
The first problem relates to the EZchange absorber bracket. This component should create a gas-tight seal between the anesthesia machine and absorbent canister. It is also designed to automatically seal the circuit when the absorbent canister is removed, as during absorbent canister changes. We found instances in which a significant leak existed both with and without the canister in place (with one case even requiring patient ventilation with a manual resuscitator to achieve adequate tidal volumes.) The problem was localized to the interconnect valve between the canister and EZchange (fig. 1). The problem seemed to be intermittent and, in some instances, was not detected or appreciated during automated checkout. The exact cause of failure of this connection is still unclear and, according to a company representative, is under investigation by the manufacturer. A solution has been to remove the EZchange assembly and mount the canister directly to the machine.
Fig. 1. EZchange assembly and associated absorbent canister. The  white arrow  identifies the component found to leak during system failures. 
Fig. 1. EZchange assembly and associated absorbent canister. The  white arrow  identifies the component found to leak during system failures. 
Fig. 1. EZchange assembly and associated absorbent canister. The  white arrow  identifies the component found to leak during system failures. 
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The second problem involves the built-in spirometry sensors. When this problem occurred, warning messages (e.g.  , tidal volume not achieved, check flow sensors, system leak) appeared, and the calculated expired tidal volumes were well below those actually delivered. Further analysis revealed that excess moisture in the breathing system (suggested by the condensation seen in the expiratory valve assembly) may lead to such malfunction of the sensors, which are located near the inspiratory and expiratory valves. A solution to this has been to switch to the backup D-Lite spirometry module included on the machines, which uses separate pressure tubing and seems to be less vulnerable to the effects of moisture in the circuit. (The machine will still give an alarm indicating that the volume sensors disagree, but the flow volume loops will appear normal.) We are also adding expiratory limb filters to our circuits to help to protect the sensors.
Users should be aware of these potential problems and solutions until the manufacturer offers definitive solutions.
*Mount Sinai School of Medicine, New York, New York.
Fig. 1. EZchange assembly and associated absorbent canister. The  white arrow  identifies the component found to leak during system failures. 
Fig. 1. EZchange assembly and associated absorbent canister. The  white arrow  identifies the component found to leak during system failures. 
Fig. 1. EZchange assembly and associated absorbent canister. The  white arrow  identifies the component found to leak during system failures. 
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