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Clinical Chemistry 51: 291-292, 2005; 10.1373/clinchem.2004.043638
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(Clinical Chemistry. 2005;51:291-292.)
© 2005 American Association for Clinical Chemistry, Inc.

Editorials

Clinical Assessment of Oxygen Transport-Related Quantities

Willem G. Zijlstra

Department of Paediatrics , University Hospital, University of Groningen, 9713 GZ Groningen, The Netherlands,

aE-mail w.g.zijlstra@bkk.azg.nl

The first 300 words of the full text of this article appear below.

By 1950, oxygen transport by the blood was well understood. The oxygen-carrying properties of the blood had been shown to be determined by oxygen capacity, oxygen saturation, and oxygen affinity, the latter expressed by a graph relating oxygen saturation (SO2) to oxygen tension (PO2), the oxygen saturation curve. Although these quantities could be determined in the physiology laboratory and although various oximeters for measuring SO2 in vivo had been developed (1)(2), examination of the oxygen transport status of patients was still based largely on clinical signs, such as cyanosis. The accurate evaluation of the oxygen capacity had to await the standardization of hemoglobinometry (3) and the complete determination of the composition of human hemoglobin (HbA) (4).

Standardization of hemoglobinometry on the basis of spectrophotometric determination of methemoglobincyanide, a stable hemoglobin derivative into which all hemoglobin derivatives usually present in the blood can be easily converted, involved an understanding that the total hemoglobin concentration (ctHb) includes the inactive (non-oxygen-binding) derivatives. Consequently, even in healthy individuals, the oxygen capacity per gram of hemoglobin is slightly lower than the theoretical value of 1.39 mL/g, calculated by dividing the molar volume of oxygen (22 394 mL at standard temperature and pressure dry) by one fourth of the molar mass of human HbA (16 114.5g). Oxygen capacity may be diminished in patients by an increased fraction of inactive hemoglobin, later called dyshemoglobin (5). The Beckman DU spectrophotometer soon enabled the measurement of the common dyshemoglobins, methemoglobin (MetHb) and carboxyhemoglobin (COHb), in the clinical chemical laboratory (6). Determination of ctHb by the standard method and correction for the fractions of MetHb and COHb thus made simple determination of the oxygen capacity possible. The validity . . . [Full Text of this Article]






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