What mixture will most anesthesia machines deliver?

What mixture will most anesthesia machines deliver?

• A. 200 mL O2/min
• B. 100% O2
• C. 50% O2/50% N2O
• D. Balanced gas mix

Answer: (A)

The key idea is that oxygen delivery must meet the body’s metabolic needs. The tissues consume about 200 mL of oxygen per minute at rest, and in anesthesia the system is designed so the fresh gas flow provides at least that amount of oxygen to prevent hypoxemia. In a circle anesthesia system, much of the gas is recirculated after CO2 removal, but the oxygen component of the fresh gas flow sets the minimum oxygen delivery. The rest of the gas in the circuit includes carrier gases and inhaled anesthetic agents, not a fixed 100% oxygen or a fixed 50/50 mix. So the practical, baseline delivery is about 200 mL of oxygen per minute to meet metabolic demand, with the overall mixture subsequently adjusted by the machine to achieve the desired anesthesia level.

The key idea is that oxygen delivery must meet the body’s metabolic needs. The tissues consume about 200 mL of oxygen per minute at rest, and in anesthesia the system is designed so the fresh gas flow provides at least that amount of oxygen to prevent hypoxemia. In a circle anesthesia system, much of the gas is recirculated after CO2 removal, but the oxygen component of the fresh gas flow sets the minimum oxygen delivery. The rest of the gas in the circuit includes carrier gases and inhaled anesthetic agents, not a fixed 100% oxygen or a fixed 50/50 mix. So the practical, baseline delivery is about 200 mL of oxygen per minute to meet metabolic demand, with the overall mixture subsequently adjusted by the machine to achieve the desired anesthesia level.