Oxygen supplementation is a cornerstone of emergency care. Room air contains only 21% oxygen, an amount insufficient for many patients presenting with breathlessness. Several devices allow us to increase the fraction of inspired oxygen delivered to a patient in distress. Among these, the Venturi device remains the most widely used.
Venturi masks operate on Bernoulli’s principle: as the velocity of a fluid (liquid or gas) increases through a constriction, its pressure falls. In the Venturi device, the velocity of pure oxygen flowing through a narrow orifice is controlled precisely. This, in turn, determines the volume of room air entrained into the device. The result is a controlled, predictable mixing that delivers a fixed fraction of inspired oxygen (FiO2) to the patient, regardless of the patient’s own breathing pattern.
Standard Venturi devices deliver FiO2 at six fixed settings: 24%, 28%, 31%, 35%, 40%, and 60%. Beyond 60% FiO2, the Venturi system reaches its practical limit, and clinicians must turn to alternative modalities: non-rebreathing masks, non-invasive ventilation, endotracheal intubation, or tracheostomy.
These devices see frequent use across intensive care units and emergency settings, including mobile ICUs. The chart below is serving as a working reference in our ICU since 2014.
Each Venturi connector is colour-coded, allowing rapid identification of its corresponding FiO2. The chart specifies the oxygen flow rate to be set, from either wall supply or cylinder, for each colour.
