OXYGEN STATUS ALGORITHM, VERSION 3, WITH SOME APPLICATIONS

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.