The main reason for the difference between the dialed vaporizer concentration and the reading on the gas monitor after induction is?

The main reason for the difference between the dialed vaporizer concentration and the reading on the gas monitor after induction is?

• A. Rapid uptake of sevoflurane
• B. Insufficient fresh gas flow for vaporizer function
• C. Second gas effect
• D. Dilution

Answer: (D)

When a volatile anesthetic is set on the vaporizer, that dial indicates the fraction of anesthetic vapor that would be added to the carrier gas, but the actual concentration delivered to the patient depends on how much fresh gas flow (FGF) is flowing through the circuit. If the fresh gas flow is high, the anesthetic vapor from the vaporizer is diluted by all the additional carrier gas. The gas monitor measures the concentration in the gas mixture that reaches the breathing circuit, so with high dilution the reading will be lower than the dial setting. After induction, higher FGF is often used to rapidly wash in oxygen and create a fresh circuit, which makes the delivered concentration appear lower on the monitor than what the dial suggests. Other phenomena like rapid uptake or the second gas effect can influence concentrations dynamically, but the principal reason the monitor reading undercuts the dial is dilution by the carrier gas due to high fresh gas flow.

When a volatile anesthetic is set on the vaporizer, that dial indicates the fraction of anesthetic vapor that would be added to the carrier gas, but the actual concentration delivered to the patient depends on how much fresh gas flow (FGF) is flowing through the circuit. If the fresh gas flow is high, the anesthetic vapor from the vaporizer is diluted by all the additional carrier gas. The gas monitor measures the concentration in the gas mixture that reaches the breathing circuit, so with high dilution the reading will be lower than the dial setting. After induction, higher FGF is often used to rapidly wash in oxygen and create a fresh circuit, which makes the delivered concentration appear lower on the monitor than what the dial suggests. Other phenomena like rapid uptake or the second gas effect can influence concentrations dynamically, but the principal reason the monitor reading undercuts the dial is dilution by the carrier gas due to high fresh gas flow.