Vaporizers for which of the following volatile anesthetics could be used interchangeably with accurate delivery of the concentration set on the vaporizer dial?

Vaporizers for which of the following volatile anesthetics could be used interchangeably with accurate delivery of the concentration set on the vaporizer dial?

• A. Halothane, sevoflurane, and isoflurane
• B. Sevoflurane and isoflurane
• C. Halothane and sevoflurane
• D. Halothane and isoflurane

Answer: (D)

The key idea is that a vaporizer is calibrated to deliver a specific fraction of anesthetic gas based on the agent’s vapor pressure and how the vapor is generated inside the device. Different volatile agents have different saturated vapor pressures, so the same dial setting doesn’t automatically translate to the same delivered concentration across different agents. Halothane and isoflurane have very similar saturated vapor pressures at room temperature, so a vaporizer dial setting that is intended to deliver a certain concentration for one of these agents will produce a closely matching concentration if the other agent is used in the same vaporizer. That’s why those two are considered interchangeable for accurate delivery. Sevoflurane has a notably different vapor pressure, and thus the dial setting calibrated for halothane or isoflurane would not yield the same concentration when sevoflurane is used, making them not interchangeable.

The key idea is that a vaporizer is calibrated to deliver a specific fraction of anesthetic gas based on the agent’s vapor pressure and how the vapor is generated inside the device. Different volatile agents have different saturated vapor pressures, so the same dial setting doesn’t automatically translate to the same delivered concentration across different agents.

Halothane and isoflurane have very similar saturated vapor pressures at room temperature, so a vaporizer dial setting that is intended to deliver a certain concentration for one of these agents will produce a closely matching concentration if the other agent is used in the same vaporizer. That’s why those two are considered interchangeable for accurate delivery.

Sevoflurane has a notably different vapor pressure, and thus the dial setting calibrated for halothane or isoflurane would not yield the same concentration when sevoflurane is used, making them not interchangeable.