Abstract
The Haldane M constant represents the ratio of oxygen/carbon monoxide affinity to hemoglobin. Findings on M values appear to be quite variable among studies. A systematic review and a meta-analysis were conducted to set a reference of human M values according to experimental conditions. The searched included all the relevant articles published from 1985 to January 2016 and extracted from the major electronic libraries database (PubMed/Embase/JSTOR). For each article, the following items were collected: age, temperature, pH, atmospheric pressure, 2,3-diphosphoglycerate (2,3-DPG) or methemoglobin levels, and hemoglobin type. Statistical analyses were performed using JMP®Pro12 software. Among the 1.683 articles analyzed, 15 were selected, which included 111 individual data, 21 mean values related to human adult hemoglobin (HbA) and 57 mean values for fetal hemoglobin (HbF) at known temperature and pH. The median M value at physiological conditions was 218 [191–257] (n = 19) for HbA and 175 [158–192] for HbF. There was a negative correlation between temperature and M value (p < 0.001), but no correlation between M and pH for HbA (p = 0.33), conversely to HbF (p = 0.044). Data were insufficient to perform a meta-analysis on the dependence between M and 2,3-DPG concentration, atmospheric pressure, pregnancy, methemoglobin, and sickle Hb. Our analysis confirmed that the M value in humans at physiological conditions is 218 for HbA and 175 for HbF. Temperature influences M, but further studies are required to clarify pH influence.
Published Version
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