Evaluation of Venturi Adapters for CPAP

Background: CPAP therapy has been shown to effectively reduce the risk of obstructive apnea and oxygen desaturation in procedural sedation. An economical approach to administering CPAP is through a Venturi adapter, which amplifies oxygen flows to produce pressures suitable for CPAP. The objective of this study was to evaluate the performance of four Venturi adapters across clinically relevant metrics including pressure-generation efficiency, inspired oxygen concentration (F_IO2), dilution of the end-tidal carbon dioxide (E_tCO2) sample for capnometry, and noise levels produced. Methods: A benchtop simulator was used to evaluate Venturi adapters. The simulator was composed of a test lung, corrugated tubing to simulate a trachea, a silicone-molded face, an air-cushioned mask strapped to the face, a high-pressure oxygen source, and several Venturi adapters. The oxygen flows required to produce specific airway pressures were measured to evaluate pressure-generation efficiency, and the noise levels produced by the Venturi adapters at these pressures were recorded. CO₂ was infused into the test lung while the lung was ventilated, and the E_tCO2 measured at the mask was compared with a reference measurement taken from the trachea. F_IO2 was evaluated by ventilating the test lung and observing the steady-state oxygen concentration in the lung. Results: Each of the Venturi adapter designs provides their unique strengths and weaknesses. There appears to be a direct trade-off between high pressure-generation efficiency and high F_IO2. There also appears to be a direct trade-off between high F_IO2 and the extent of dilution in the E_tCO2 sample. Some Venturi adapters produce high noise levels, which might result in patient discomfort and clinician unwillingness to use. Conclusion: Variations in Venturi adapter designs create different clinical benefits. Clinicians should choose the Venturi adapter to best suit their present clinical needs.