The Figge-Fencl Quantitative Physicochemical Model
of Human Acid-Base Physiology (Version 2.0)
by James J. Figge, MD, MBA, FACP
Copyright 2003 - 2011 James J. Figge.
Originally published 22 January, 2007;
updated November - December, 2010;
published 11 January, 2011
on www.Acid-Base.org and www.Figge-Fencl.org.
Statistical Validation of the Figge-Fencl Quantitative
Physicochemical Model (Version 2.0)
Figure 1. pH of albumin-containing solutions as calculated by the
Figge-Fencl quantitative physicochemical model (version 2.0) (y-axis), versus
measured pH (x-axis). Experimental data cover the pH range of 6.85 to 7.94. Experimental
data (n = 65) are from Figge, Rossing and Fencl, J Lab Clin Med. 1991; 117: 453-467.
The slope of the regression line is 1.0059 (98% confidence limits: 0.9664 to 1.0455). Thus,
the slope is not significantly different than 1.0. The intercept is -0.0398.
R = 0.99157, and R2 = 0.9832.
Figure 2. pH of filtrands of human sera as calculated by the
Figge-Fencl quantitative physicochemical model (version 2.0) (y-axis), versus
measured pH (x-axis). Experimental data cover the pH range of 7.02 to 7.79. Experimental
data (n = 72) are from Figge, Rossing and Fencl, J Lab Clin Med. 1991; 117: 453-467.
The slope of the regression line is 1.0785 (98% confidence limits: 1.0288 to 1.1282). Thus,
the slope in this case, where both albumin and globulins are present, is significantly greater
than 1.0. The intercept is -0.5807.
R = 0.98715, and R2 = 0.9745. This analysis indicates that, although the
predictive power of the Figge-Fencl model is very good, there is a small
contribution attributed to plasma globulins that is not explained by the model. Due to the marked
heterogeneity of globulins, a detailed analysis of the quantitative contribution of
globulins to acid-base balance is still under investigation.