Clinical relevance of ventilation-perfusion inequality determined by inert gas elimination.

The first part of this review deals with the basic mechanisms and factors determining hypoxaemia and hypercapnia and the different approaches used in clinical practice and in clinical research to assess the presence of ventilation-perfusion mismatching, shunt and diffusion limitation for oxygen, and more specifically the multiple inert gas elimination technique (MIGET), in pulmonary medicine. The second part reviews three different respiratory disorders where the complex interplay between intrapulmonary and extrapulmonary factors regulating oxygen are essentially interpreted through the results afforded by the MIGET over the last decade. The gas exchange response to bronchodilators in bronchial asthma, an airway disease, and then the major determinants governing abnormal gas exchange in acute pulmonary embolism, a pulmonary vascular disorder, and during haemodialysis, a respiratory entity of extrapulmonary origin, are successively explored in the light of the inert gas method.