Performance Characteristics of Five Models of Air-Oxygen Blenders under Various Simulated Clinical Conditions

Abstract

High frequency ventilation, more powerful ventilators, and wider use of high-flow systems place increased performance demands on air-oxygen blenders. Methods: To determine the adequacy of currently available commercial blenders for these applications, we evaluated five different models at various source pressures, fractional delivered oxygen (FDO₂) settings, and auxiliary flow outputs. Results: Output in L/min increased progressively as driving pressure was raised from 40 to 50 to 60 psi. At FDO₂ 0.60, the average main output flow of the five blenders was 33% higher than it was at FDO₂ 0.21 and 29% higher than it was at FDO₂ 1.00. Use of the auxiliary flowmeter in the "flush" position substantially reduced flow from the blender's main output port. With the two models that have paired oxygen and air internal step-down regulators, these changes never dropped main output flow below approximately 130 L/min (Puritan-Bennett Air/O₂ Mixer) and 120 L/min (Veriflo MR 120 Oxygen Controller). However, the more compact blenders (Bird 3300 HL High/Low Blender, Bird 960 Air Mixer, and Sechrist 3500 Air/O₂ Mixer), which have only one internal regulator for each gas, had lower overall output under the test conditions. All three, and the Sechrist in particular, had flows that could fall short of peak ventilator demands. Conclusion: Blender gas-delivery capabilities should be considered when ventilators or techniques demanding very high output flows are studied or put into clinical use.