Multiple Inert Gas Elimination Technique: Current Methodology at the US Army Institute of Surgical Research

摘要

The intrapulmonary causes of hypoxemia include alveolar hypoventilation, ventilation-perfusion (VA/Q) inequality, shunt, and diffusion limitationto oxygen. In the late l970s, P.D. Wagner developed the Multiple Inert Gas Elimination Technique (MIGET), a method of assessing VA/Q inequality(VA/Q mismatch) and shunt. It can also be used to measure diffusion limitation. In MIGET, the lung is considered as a set of 50 respiratory units, each with a different VA/Q ratio. Six inert gases of varying solubility are infused, and the arterial, mixed venous, and expired air 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 VA/Q mismatch in a relatively low-risk, non-invasive fashion. This report describes the MIGET methodology from atechnical standpoint, as currently performed at this Institute.