Venturi Mask

A Venturi mask, also known as an air-entrainment mask, is a medical device designed to deliver a precise and fixed concentration of oxygen (fraction of inspired oxygen, FIO2) to patients needing respiratory support. Unlike simple face masks or nasal cannulas, the Venturi mask’s design ensures a constant oxygen delivery regardless of the patient’s breathing pattern.

Here’s a breakdown of its features and how it works:

How it works

The Venturi mask operates on the principle of the Venturi effect or jet mixing.

• Oxygen flow through a constricted orifice: Oxygen from a supply tank or wall outlet is delivered through a narrow orifice (small opening or jet) within the Venturi device attached to the mask.
• Pressure drop and air entrainment: As the oxygen passes through the constricted orifice, its velocity increases, creating a drop in pressure (subatmospheric pressure) at the sides of the stream. This pressure drop draws in a predictable amount of room air through side ports on the Venturi device.
• Oxygen and air mixing: The oxygen and the entrained room air mix, and this mixture is then delivered to the patient through the mask. The side holes on the mask allow the exhaled gases to escape, preventing rebreathing and avoiding an increase in the dead space.

Key features

• Fixed Performance: Venturi masks are considered fixed-performance devices (or high-air-flow oxygen enrichment devices, HAFOE) because they deliver a predictable and consistent FiO₂. This is crucial for conditions where a specific oxygen level is required, particularly for patients whose ventilation relies on the hypoxic drive (e.g., some patients with COPD).
• Color-coded adapters/valves: The Venturi device comes with various color-coded adapters or valves, each designed to deliver a specific FiO₂ at a corresponding oxygen flow rate. For example, a blue adapter might deliver 24% oxygen, while a white adapter might deliver 35%. This allows for easy selection and adjustment of the desired oxygen concentration.
• High flow rates: Venturi masks are high-flow devices that deliver a mixture of oxygen and air at a rate greater than the patient’s peak inspiratory flow, further ensuring a constant FiO₂.
• Reduced rebreathing: The mask’s design and the high fresh gas flow rate minimize the risk of rebreathing exhaled carbon dioxide.
• Versatility: Venturi masks are used in a variety of clinical settings, including emergency rooms, hospital wards, and even home care.