The Mapleson D breathing circuit is FALSE in which statement?

The Mapleson D breathing circuit is FALSE in which statement?

• A. It is a semi-open breathing system
• B. It has a proximal fresh gas inflow and a distal overflow valve
• C. With an inspiratory to expiratory ratio of 1:2, rebreathing is eliminated with spontaneous ventilation when the fresh gas flow is 3 times the minute ventilation
• D. To eliminate rebreathing, higher fresh gas flows are needed with controlled ventilation than with spontaneous ventilation

Answer: (D)

Mapleson D is a semi-open system with fresh gas inflow near the patient and an expiratory outlet toward the machine. Rebreathing depends on how well the fresh gas flow flushes exhaled CO2 from the circuit between breaths. When breathing spontaneously, the patient’s own inspiratory effort can draw gas from the circuit, so a relatively high fresh gas flow is needed to prevent rebreathing (roughly 2–3 times the minute ventilation). With controlled ventilation, the ventilator delivers a steady, predictable flow that more effectively clears the circuit, so the needed fresh gas flow to avoid rebreathing is not higher—and is typically similar to or somewhat greater than the minute ventilation, not higher than in spontaneous ventilation. Therefore, the claim that higher fresh gas flows are required with controlled ventilation than with spontaneous ventilation is not correct.

Mapleson D is a semi-open system with fresh gas inflow near the patient and an expiratory outlet toward the machine. Rebreathing depends on how well the fresh gas flow flushes exhaled CO2 from the circuit between breaths. When breathing spontaneously, the patient’s own inspiratory effort can draw gas from the circuit, so a relatively high fresh gas flow is needed to prevent rebreathing (roughly 2–3 times the minute ventilation). With controlled ventilation, the ventilator delivers a steady, predictable flow that more effectively clears the circuit, so the needed fresh gas flow to avoid rebreathing is not higher—and is typically similar to or somewhat greater than the minute ventilation, not higher than in spontaneous ventilation. Therefore, the claim that higher fresh gas flows are required with controlled ventilation than with spontaneous ventilation is not correct.