The Multiple Inert Gas Elimination Technique: A User's Manual
United States Army Institute of Surgical Research San Antonio United States
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The Multiple Inert Gas Elimination Technique MIGET is a method of assessing ventilationperfusion VAQ inequalities, shunt, and diffusion limitation. It was initially developed as a means of quantifying VAQ mismatch as an intrapulmonary cause of hypoxemia. The lung is viewed as a set of 50 respiratory units, each with a distinctive VAQ ratio. Six inert gases of varying solubility in blood are infused, and the arterial and expired gas concentrations of the gases are measured under steady-state conditions. Then, distribution of blood flow and ventilation to each of the 50 compartments is calculated. Although technically challenging, this method can be applied in a wide range of basic and clinical settings, and enables the evaluation of VAQ mismatch in a relatively low-risk, non-invasive fashion. This report describes the MIGET methodology from a technical standpoint, as currently performed at the U.S. Army Institute of Surgical Research USAISR. General set up, assessment of gas chromatograph GC linearity, preparation and infusion of the 6-gas solution, specimen collection and processing, and data analysis are covered in detail. Creation of a novel, complex, multi-ramped GC program is described.