A re-appraisal of the tri-axial chart for monitoring arterial acid-base values.
OBJECTIVE
To demonstrate the practicability of a tri-axial chart for the graphical and quantitative monitoring of arterial pH, arterial carbon dioxide partial pressure (PaCO2) and actual arterial bicarbonate-ion concentration (a[HCO3-]) in intensive care patients.


METHODS
Case report.


METHODS
A general intensive care unit (ICU).


METHODS
Using a standard mathematical transformation, a data set of pH, log PaCO2 and log a[HCO3-] values can be transformed in such a way that a graphical display of all three variables is possible while being faithful to their linear relationship. Remarkably, the graphical display closely resembles the tri-axial chart that Hastings and Steinhaus described in 1931 for studying displacements of the acid-base balance. Two new monitoring parameters based on the chart and the transformation are described. One monitors the abnormality of the acid-base status while the other monitors the rate of acid-base changes.


CONCLUSIONS
With the tri-axial acid-base chart, the complete acid-base status can be faithfully monitored. Moreover, the proposed monitoring parameters provide extra information about the arterial acid-base status that, otherwise, would remain hidden.
Hekking
M
M
Department of Medical Informatics, Erasmus University Rotterdam, The Netherlands. hekking@mi.fgg.eur.nl
Ulenkate
H J
HJ
Speelberg
B
B
Van Puyenbroek
M J
MJ
Goldschmidt
H M
HM
Gelsema
E S
ES
D000137:Acid-Base Imbalance / Q000097:blood*; D001158:Arteries; D001639:Bicarbonates / Q000097:blood; D002245:Carbon Dioxide / Q000097:blood; D003422:Critical Care; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008432:Mathematical Computing; D008499:Medical Records; D008875:Middle Aged
D001639:Bicarbonates; D002245:Carbon Dioxide