New anesthesia machines automatically check essential gas flow and ventilator functions. How reliably do these automated checks verify that the anesthesia machine can provide oxygen, allow unobstructed ventilation, allow positive pressure ventilation, and not have leaks in the circuit?
Dr. Michael P. Dosch, Nurse Anesthesia, University of Detroit Mercy, Detroit, Michigan, used layers of plastic material from the wrap enclosing the facemask to completely occlude the junction between the corrugated expiratory or inspiratory limb of the plastic portion of the breathing circuit and its mount on the machine in order to determine what would happen during automated checkout of either the Aisys, ADU (both by GE Healthcare Inc., Madison, Wisconsin), or Apollo (Dräger Medical Inc., Telford, Pennsylvania) anesthesia machines. The results were published in last month’s edition of Anesthesia & Analgesia in the article titled “Automated Checkout Routines in Anesthesia Workstations Vary in Detection and Management of Breathing Circuit Obstruction.”
In the case of expiratory limb obstruction, the Aisys anesthesia machine displayed an error message and advised “Check flow censors,” though the user could accept the condition and initiate patient care. Once care was initiated, the message “PEEP high. Blockage?” appeared. When the inspiratory limb was obstructed, the ventilator check failed, though again, the user could start the case.
Using the ADU machine, when the expiratory limb was occluded, checkout failed (the error message used the word “failed” twice), and when the inspiratory limb was occluded, the error message “probable disconnection”appeared.
For the Apollo machine, one of two error messages occurred for either inspiratory or expiratory occlusion. “System error. Device cannot be used” was an unrecoverable error message. The machine had to be turned off, and then on, for the error message to disappear. The other error message identified the problem as a leak in the breathing circuit or ventilator. For both the ADU and Apollo machines, patient care could not be initiated in the presence of an occlusion.
The results of this study are illuminating. We increasingly rely on the automated assessment by the anesthesia machine that it will function as expected at the start of anesthesia. Users should be aware of how their machines will respond to either inspiratory or expiratory obstruction during automatic checkout. All users should be fully in-serviced on every anesthesia machine in use a facility, because the checkout procedures and machine responses are not consistent.