Venturi mask provides fixed oxygen concentrations by mixing oxygen with inhaled air using a mask and reservoir bag.

• A. A face mask that delivers a fixed oxygen concentration by mixing oxygen with inhaled air
• B. A simple nasal cannula delivering variable flow
• C. A bag-valve mask used for manual ventilation
• D. A Venturi mask delivers fixed concentrations by mixing oxygen with inhaled air

Answer: (D)

The essential idea is how certain oxygen delivery devices provide a precise, fixed inspired oxygen concentration. A Venturi mask achieves this by using a calibrated oxygen jet and entrainment mechanism that mixes a defined amount of ambient air with pure oxygen, producing a specific FiO2 set by the adapter. This fixed concentration remains stable across different breathing patterns, which is why it’s preferred when exact oxygen targets are needed (for example, in COPD). It’s important to note that this device delivers the set FiO2 without relying on a reservoir bag, unlike some other masks. The other options describe devices that do not offer a fixed FiO2: a simple nasal cannula provides variable FiO2 based on flow and breathing; a bag-valve mask is for manual ventilation and not a device that calibrates a fixed oxygen concentration; and a nonrebreather mask concentrates oxygen but its delivered FiO2 can vary with fit and effort.