The minimum oxygen flow rate recommended for a simple (Hudson type) facemask is:

• A 1 L/min
• B 3 L/min
• C 5 L/min ✓
• D 10 L/min

Explanation

A simple facemask has no reservoir and the mask itself acts as dead space. A flow of at least 5 L/min is required to wash out exhaled carbon dioxide from the mask between breaths and prevent rebreathing. Below this flow, CO2 accumulates in the mask volume. Typical flows are 5 to 10 L/min, delivering an FiO2 of roughly 40 to 60%, though the exact concentration is uncontrolled because entrained room air dilutes the gas.

Reference: Egan's Fundamentals of Respiratory Care, 12th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.