Methods and Guidelines for Mechanical Ventilation with Helium-Oxygen for Severe Upper-Airway Obstruction

Abstract

We report a case of severe airway obstruction just above the carina which required the blending of helium and oxygen during mechanical ventilation with an Emerson 3-MV ventilator. We subsequently investigated the predictability of helium's flow rates through oxygen-calibrated flowmeters to determine whether the relative diffusibility factor of 2.8 stated in the literature was accurate for the proportioning of oxygen with helium at all flowrates. We found that helium flow through three different commercial oxygen flowmeters varied significantly from the predicted factor and varied significantly among flowmeters. When premixed helium and oxygen cannot be obtained, it is feasible to mix pure helium and oxygen, provided a flow meter is precalibrated for helium. Accurate proportioning of helium with oxygen is dependent on helium's viscosity and density, which determine its final flowrate in an oxygen-calibrated flowmeter. The Emerson 3-MV ventilator proved ideal for the delivery of He-O₂ mixtures because it does not internally consume gas and because it has a simple gas-blending system. (TenEyck LG, Colgan FJ. Methods and Guidelines for Mechanical Ventilation with Helium-Oxygen for Severe Upper-Airway Obstruction. Respir Care I 984;29;155-159.