Which device reduces high gas pressure from cylinders to a safe operating level (below 50 psig) in modern anesthesia machines?

• A. Two-stage pressure regulator
• B. One-stage pressure regulator
• C. Flow restrictor
• D. Pressure relief valve

Answer: (A)

High-pressure gas inside cylinders is far above what the anesthesia machine can safely use, so a regulator is needed to bring that pressure down to a stable, safe level. A two-stage pressure regulator accomplishes this in two steps: the first stage drops the cylinder pressure to an intermediate level, and the second stage reduces it further to a safe operating pressure below 50 psig. This staged approach keeps downstream pressures steady even as cylinder pressure falls during use, ensuring reliable and accurate gas delivery to the patient.

A one-stage regulator would also lower pressure, but it’s more sensitive to variations in cylinder pressure, leading to larger fluctuations in the pressure seen by downstream components. A flow restrictor only limits flow and does not set or regulate pressure. A pressure relief valve protects against overpressure by venting when pressure is too high, but it does not regulate normal operating pressure.