anticoagulant, such as heparin, and transported to the hospital laboratory at
4 oC. Care must be taken that air does not enter any blood samples during
collection. The concentration of H+ and PCO 2 level are measured directly using
an automated analyzer that is also programmed to calculate the corresponding
concentration of HCO 3 – (Figure 9.10) according to the Henderson-Hasselbalch
equation. An acidosis or alkalosis can be identified from the pH, that is the
concentration of H+, in the blood. An examination of the levels of PCO 2 and
HCO 3 – shows whether the identified disorder is metabolic or respiratory in
origin and indicates to what extent compensation is occurring.X]VeiZg./ DISORDERS OF ACID–BASE BALANCE
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Figure 9.10 (A) An automated analyzer
for determining blood pH and PCO 2 and
programmed to calculate the corresponding
concentration of HCO 3 –. (B) A sample of a read
out from the automated analyzer. Courtesy of the
Department of Clinical Biochemistry, Manchester
Royal Infirmary, UK.B)