A sevoflurane vaporizer will deliver an accurate concentration of an unknown volatile anesthetic if it shares which property with sevoflurane?

A sevoflurane vaporizer will deliver an accurate concentration of an unknown volatile anesthetic if it shares which property with sevoflurane?

• A. Molecular weight
• B. Viscosity
• C. Vapor pressure
• D. Blood/gas partition coefficient

Answer: (C)

Vaporizer output is dictated by the saturated vapor pressure of the agent at the operating temperature. A sevoflurane vaporizer is calibrated so that a given dial setting yields a specific fraction of vapor in the carrier gas based on the agent’s vapor pressure. If another volatile anesthetic has the same saturated vapor pressure as sevoflurane at room temperature, the same dial setting will deliver approximately the same concentration of vapor in the fresh gas flow, making the unknown agent delivered accurately. Molecular weight, viscosity, and the blood/gas partition coefficient affect pharmacokinetics and physical flow, uptake, or potency, but they do not determine how much vapor the vaporizer produces for a given setting. Hence they don’t guarantee accurate concentration, whereas matching vapor pressure does.

Vaporizer output is dictated by the saturated vapor pressure of the agent at the operating temperature. A sevoflurane vaporizer is calibrated so that a given dial setting yields a specific fraction of vapor in the carrier gas based on the agent’s vapor pressure. If another volatile anesthetic has the same saturated vapor pressure as sevoflurane at room temperature, the same dial setting will deliver approximately the same concentration of vapor in the fresh gas flow, making the unknown agent delivered accurately.

Molecular weight, viscosity, and the blood/gas partition coefficient affect pharmacokinetics and physical flow, uptake, or potency, but they do not determine how much vapor the vaporizer produces for a given setting. Hence they don’t guarantee accurate concentration, whereas matching vapor pressure does.