M. Siggaardandersen et O. Siggaardandersen, OXYGEN STATUS ALGORITHM, VERSION 3, WITH SOME APPLICATIONS, Acta anaesthesiologica Scandinavica, 39, 1995, pp. 13-20
The Oxygen Status Algorithm is a computer program which uses measureme
nts from a pH & blood gas analyser and a haemoximeter to calculate the
oxygen status and the acid-base status of the arterial blood. Version
3 features on-line data collection from the analyser; storage of up t
o 2000 patient cases in a Lotus 123 file format: printing of a Cumulat
ed Patient Report in addition to the Patient Status Report; combinatio
n of arterial and mixed venous data for calculation of the shunt and t
he oxygen consumption rate (when cardiac output is keyed in); calculat
ion of reference values for fetal haemoglobin for newborns (when gesta
tional age is keyed in). Examples of applications answer the following
questions: 1) Does hyperventilation improve the oxygen supply to the
tissues? No, for a normal person a slight hypoventilation with a pCO(2
) of 8.5 kPa provides a maximal oxygen extraction tension. 2) What is
the optimal hyperventilation at the top of Mt. Everest (ambient pressu
re 33 kPa)? Hyperventilation to a pCO(2) of about 1.4 kPa provides a m
aximal oxygen extraction tension of 2.4 kPa for an unacclimatized pers
on. 3) Which change in haemoglobin oxygen affinity would be equivalent
to a decrease in arterial pO(2) to 6.3 kPa? The oxygen extraction ten
sion would decrease to 4.0 kPa and the same value would be caused by a
decrease in half-saturation tension to 2.8 kPa, a decrease which coul
d be due to a moderate alkalaemia (pH = 7.54) combined with a moderate
ly decreased 2,3-diphosphoglycerate concentration (3.4 mmol/L). 4) Is
temperature correction of the measured pO(2) and pCO(2) to the actual
body temperature needed? Yes, for example, omitting temperature correc
tion even when the patient temperature is only slightly decreased to 3
6 degrees C would result in a negative value For the calculated arteri
o-venous shunt fraction when the actual value, using temperature corre
ction, is 11%. 5) Does the alpha-stat approach of pCO(2) and pH regula
tion in hypothermia, where pH is allowed to rise as in blood in vitro,
cause a fall in mixed venous pO(2) below the critical value? No, alth
ough the mixed venous pO(2) will be lower than with the pH-stat approa
ch (constant pH at body temperature), it remains above the critical mi
xed venous pO(2) level. The program is intended for clinical routine u
se as well as teaching purposes. It has context sensitive help as well
as an extensive help index. A number of ''demo'' cases are provided w
ith annotations in a separate file.