－33－ Analysis of the Acid-Base Balance in Arterial Blood Plasma of Elderly Patients

We have previously found that in the normal blood, where a metabolic component of pH, pHo, was ignored, a respiratory component, pH*, was given by a linear logarithmic function of Pco2,; pHo was then obtained by subtracting pH * from the measured value for pH. Analysis of the acid‐base imbalance was greatly facilitated by this division of pH into its metabolic and respiratory components. In arterial blood of elderly patients, the regression functions of pH and pH * against pHo were linear. Pco2 was also linearly related to pHo, whereas pH * showed a reciprocal relation to pHo. It was then establishied that about 26 % of pHo was compensated for by the change in pH*, so the change in pH was limited to 74 % of the change in pHo. Since pH is the sum of pH * and pHo, the deviations of the individual points of pH and pH * from the respective regression lines became equal. Designating the pH and pH * values on the respective regression lines by pH and pH*, pH－pH became equal to pH*－pH*, because pH－pH * = pH－pH*