Which flowmeter is positioned closest to the common gas outlet?

• A. N2O
• B. O2
• C. Air
• D. CO2

Answer: (B)

The flowmeter for oxygen (O2) is positioned closest to the common gas outlet in an anesthesia machine for several important reasons. Oxygen is considered the most crucial gas in anesthesia, as it is vital for patient survival. Placing the oxygen flowmeter nearest to the common gas outlet ensures that it is the last gas to mix with other gases before delivery to the patient. This arrangement helps in reducing the risk of hypoxic mixtures.

In the event of a failure in the flowmeter or an inadvertent error, such as the displacement of other gases, having oxygen closest to the outlet guarantees that a constant supply of oxygen is always available to the patient. Additionally, it aligns with safety protocols to promote the use of oxygen as a primary agent, ensuring that even if other gas flowmeters are left open accidentally, oxygen concentration remains adequate.

This positioning follows established guidelines and standards in anesthesia practice, which prioritize oxygen to ensure safety and efficacy in patient care.