Journal of Applied Physiology, Vol 77, Issue 1 332-351, Copyright © 1994 by American Physiological Society

ARTICLES

Pulmonary capillary transport function from flow-limited indicators

S. H. Audi, G. S. Krenz, J. H. Linehan, D. A. Rickaby and C. A. Dawson
Biomedical Engineering Department, Marquette University, Milwaukee 53233.

The objective of this study was to examine the use of rapidly diffusing (flow-limited) indicators for estimating the pulmonary capillary blood volume (i.e., fraction of the lung blood volume wherein the diffusible indicators equilibrate with the tissue) and the capillary transit time distribution. Supporting theory and an application to experimental data are presented. The theory leads to the following equations, which relate the mean transit time (t), the variance (sigma 2), and the third central moment (m3) of the capillary transport function, hc(t), to the moments of the venous concentration-time curves for a vascular reference indicator, CR(t), and a flow-limited diffusible indicator, CD(t), after a bolus injection of the indicators upstream from an organ: sigma 2D - sigma 2R = ([1 + (te/tc)]2-1)sigma 2c and m3D-m3R = ([1 + (te/tc)]3-1)m3c, where te = tD - tR and tc is capillary t. The moments of hc(t) can be estimated if the injected bolus includes, along with the vascular reference indicator, at least two flow-limited diffusible indicators, each with a different te. A least-squares optimization procedure can then be used to specify the moments of hc(t). This approach was applied to isolated dog lung lobes with [14C]-diazepam as the diffusible indicator. The tissue-to-perfusate partition coefficient for [14C]diazepam could be adjusted to any desired value by altering the perfusate albumin concentration. Thus, by making a number of injections, each at a different perfusate albumin concentration, data were obtained in a manner equivalent to making one injection with a number of flow-limited diffusible indicators, each with a different te. On average, the estimated capillary volume and mean transit time were approximately 48% of the total lobar volume and mean transit time, and the relative dispersion of the hc(t) was approximately 75%.

This article has been cited by other articles:

				F. Qiao, D. R. Trout, V. M. Quinton, and J. P. Cant A compartmental capillary, convolution integration model to investigate nutrient transport and metabolism in vivo from paired indicator/nutrient dilution curves J Appl Physiol, September 1, 2005; 99(3): 788 - 798. [Abstract] [Full Text] [PDF]

				K. O'Neill, J. G. Venegas, T. Richter, R. S. Harris, J. D. H. Layfield, G. Musch, T. Winkler, and M. F. V. Melo Modeling kinetics of infused 13NN-saline in acute lung injury J Appl Physiol, December 1, 2003; 95(6): 2471 - 2484. [Abstract] [Full Text]

				S. H. Audi, R. D. Bongard, C. A. Dawson, D. Siegel, D. L. Roerig, and M. P. Merker Duroquinone reduction during passage through the pulmonary circulation Am J Physiol Lung Cell Mol Physiol, November 1, 2003; 285(5): L1116 - L1131. [Abstract] [Full Text] [PDF]

				D. L. Roerig, S. H. Audi, J. H. Linehan, G. S. Krenz, S. B. Ahlf, W. Lin, and C. A. Dawson Detection of changes in lung tissue properties with multiple-indicator dilution J Appl Physiol, June 1, 1999; 86(6): 1866 - 1880. [Abstract] [Full Text] [PDF]

				A. V. Clough, S. T. Haworth, C. C. Hanger, J. Wang, D. L. Roerig, J. H. Linehan, and C. A. Dawson Transit time dispersion in the pulmonary arterial tree J Appl Physiol, August 1, 1998; 85(2): 565 - 574. [Abstract] [Full Text] [PDF]

				R. G. Tirona, A. J. Schwab, W. Geng, and K. S. Pang Hepatic Clearance Models. Comparison of the Dispersion and Goresky Models in Outflow Profiles from Multiple Indicator Dilution Rat Liver Studies Drug Metab. Dispos., May 1, 1998; 26(5): 465 - 475. [Abstract] [Full Text]

				S. H. Audi, C. A. Dawson, J. H. Linehan, G. S. Krenz, S. B. Ahlf, and D. L. Roerig Pulmonary disposition of lipophilic amine compounds in the isolated perfused rabbit lung J Appl Physiol, February 1, 1998; 84(2): 516 - 530. [Abstract] [Full Text] [PDF]