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Performance of erroneously filled sevoflurane, enflurane and other agent-specific vaporizers
1Department of Anesthesiology, Mount Sinai School of Medicine of the City University of New York, NY 10029-6574, USA.
Objective:
Erroneous filling of an agent-specific anesthesia vaporizer may result in concentration and potency outputs that are very different from those expected from the concentration dial setting. Enflurane and sevoflurane have relatively similar saturated vapor pressures (SVPs 175 mmHg and 160 mmHg, respectively, at 20 degrees C) and potencies (MACs 1.68% and 2%, respectively). We derived an equation to relate the vapor concentration output of an agent-specific vaporizer to the gas inflow splitting ratio (SR) created by the vaporizer and the SVP of the potent inhaled agent.
Methods:
To test the validity of this equation, we filled an Enfluratec 4 enflurane vaporizer with sevoflurane and a Penlon PPV Sigma sevoflurane vaporizer with enflurane and compared the vapor concentration outputs with our predictions.
Results:
The equation accurately predicted the vapor concentration outputs of the erroneously filled enflurane and sevoflurane vaporizers. The potency (MAC) output of the erroneously filled Enfluratec 4 vaporizer decreased by 22%-33%, and that of the Penlon PPV Sigma sevoflurane vaporizer increased by 21%-31% from those expected from the concentration dial settings.
Conclusion:
When an agent-specific variable bypass vaporizer is erroneously filled, the vapor concentration outputs can be predicted from the splitting ratio created by setting the vaporizer concentration dial and the SVP of the agent.
