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Performance evaluation of a draw-over vaporizer with a nonbreathing circuit during simulated adverse conditions
1Department of Anesthesia, Stanford University School of Medicine, CA 94305.
Study Objective:
Performance evaluation of a draw-over vaporizer with a nonrebreathing circuit during simulated adverse conditions.
Design:
Open laboratory study.
Setting:
University hospital laboratory.
Materials And Interventions:
The output (%) of a temperature-compensated Ohmeda Cyprane PAC (portable anesthesia complete) draw-over vaporizer (Ohmeda, Madison, WI) using isoflurane attached to a nonrebreathing circuit was tested in the laboratory during manual ventilation under normal and simulated adverse conditions. The adverse conditions tested were high ambient temperature and static and dynamic positional variation.
Measurements And Main Results:
The results show that the output bias of the PAC vaporizer has a generally consistent profile as tested, except when placed in the 180 degrees full-inversion or 90 degrees anterior-tilt position. We also conducted trials with the Penlon ventilator (Ohmeda, Abingdon, Oxford, U.K.) attached to the circuit at each of its input ports. Ventilation at one input port produced dangerously high airway pressures (within the circuit), thus supporting the manufacturer's recommendation against the use of this port for positive-pressure ventilation. Using the recommended port, the test lung was seen to inflate and deflate appropriately, but, surprisingly, no vapor output was detected by the agent monitor at any vaporizer setting when using the ventilator at the recommended port.
Conclusion:
Anesthetists should be aware of the pitfalls and possible problems that may be associated with this type of anesthetic delivery system.