RELATIONSHIPS AMONG VENTILATION-PERFUSION DISTRIBUTION, MULTIPLE INERT GAS METHODOLOGY AND METABOLIC BLOOD-GAS TENSIONS

Until 1974, physiologists described the ventila-tion-perfusion (V\/Q) aspects of the lung by grouping together the various blood/air inter-active sites into two perfused "compartments", shunt and an "alveolar " compartment, and the unperfused deadspace (Briscoe, 1959; Farhi and Yokoyama, 1967). The landmark paper (Wagner, Salzman and West, 1974) on the multiple inert gas method of determining the detailed distribution of the cardiac output between shunt and 48 alveolar "compartments " offered far more in-formation. Two quotations from that paper summarize their achievements; a third sets a warning: "Measurements with several foreign gases such as krypton and xenon (29) and methane, ethane and nitrous oxide (34) have been used to gain information about distributions of Vh/Q ratios. However, these analyses, as with the oxygen methods, have been limited to a small number of compartments. " (p. 588.) "This paper describes a method for deter-mining virtually continuous distributions of V\/Q ratios. " (p. 588.) "The question arises as to how it is possible to recover 50 compartments with far fewer inde-pendent equations. The answer to this is not clear and we do not propose to consider it in any detail in this paper. " (p. 591.) Since that time some 100 papers and chapters, on the multiple inert gas method, theoretical and applied, have appeared in the literature. Im