Table 1.
Explanation for symbols and constants.
Fig 1.
Fig 1 shows that [H+] in a fluid mixed 1:1 is not a simple function of the [H+] in the individual fluids.
Blue line represents identity. The resulting [H+] is never higher than the mean [H+].
Fig 2.
Fig 2 shows that pH in a 1:1 mixture is not predictable from pH in the constituent fluids.
Fig 3.
Fig 3 shows the overall fit for all data using a mixed model with random intercept.
The thick blue line shows the population regression, the red line shows X = Y.
Fig 4.
Fig 4 shows the fit obtained with the activity coefficients corrected after Davies [15].
The blue line is the population estimate from a mixed model with random intercept. The intercept is not significantly different from 0 and the slope not different from 1.
Fig 5.
Fig 5 shows the prediction obtained by unbiased nonparametric regression (blue line) in comparison with the line of identity (red).
Fig 6.
Fig 6 shows a Bland-Altman plot of fitted-measured pH versus mean of fitted and measured pH.
The lines indicate mean and 95% confidence interval.
Fig 7.
Fig 7 shows relationship between the standard deviations of the differences between modeled and estimated pH as a function of the corresponding means for the 76 patients.
The area of the circles is proportional to sample size.
Fig 8.
Fig 8 shows the fit obtained after assigning buffer with 6 mM pKa 7 to all samples represented by scatterplot, red line of identity and blue line of population mean.
Fig 9.
Fig 9 shows the time course of measured and modeled pH (red curve) in one of the longest series.
Fig 10.
Fig 10 shows the time course of measured and modeled pH (red curve) in one of the longest series.