Which flow rate can create a risk of rebreathing carbon dioxide in a low-flow delivery system?

In a low-flow delivery system, the risk of rebreathing carbon dioxide increases when the flow rates are below the patient's minute ventilation. This is because low-flow systems do not supply enough oxygen to meet the patient's needs, leading to inadequate elimination of exhaled carbon dioxide from the breathing circuit.

When flow rates are below the minute ventilation, the amount of fresh gas delivered is insufficient to displace the carbon dioxide being exhaled. Consequently, the exhaled carbon dioxide can accumulate in the breathing circuit, increasing the risk of rebreathing. This is particularly concerning in situations where a patient has a high minute ventilation due to factors like elevated respiratory rate or increased tidal volume.

In contrast, using flow rates above or exactly at the patient's minute ventilation would provide sufficient fresh gas flow to prevent the accumulation and rebreathing of carbon dioxide, mitigating this risk. Consequently, higher flow rates can adequately clear exhaled gases from the system, enhancing patient safety and comfort.