# Figge-Fencl Quantitative Physicochemical Model

of Human Acid-Base Physiology

by James J. Figge, MD, MBA, FACP

##### Copyright 2003 - 2009 James J. Figge.

Updated 22 December, 2007; 28 December, 2008.

Updated version published 15 January, 2009 on

*www.Acid-Base.org* and *www.Figge-Fencl.org*.

# Statistical Validation of the Figge-Fencl Quantitative
Physicochemical Model

**Figure 1. pH of albumin-containing solutions as calculated by the
Figge-Fencl quantitative physicochemical model (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 0.9987 (98% confidence limits: 0.9592 to 1.0381). Thus,
the slope is not significantly different than 1.0. The intercept is 0.0211.
R = 0.99146, and R^{2} = 0.9830.

**Figure 2. pH of filtrands of human sera as calculated by the
Figge-Fencl quantitative physicochemical model (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 1.0714 (98% confidence limits: 1.0226 to 1.1201). Thus,
the slope is significantly different than 1.0. The intercept is -0.5217.
R = 0.98746, and R^{2} = 0.9751. 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.