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HbO.compare

Compare Models of Hemoglobin O2 saturation curve at varied levels of PCO2 and pH.

Model number: 0035

Description

Compare various hemoglobin-oxygen binding models. Separate models for Adair, Dash, and Hill. Also, Total blood oxygen model and hemoglobin-CO2 binding model.

• Dash model: Hb-O2 sauration curves showing Bohr effect (higher CO2 reducing the affinity of Hb for O2, Lower pH does similarly. (DPG is 4.65 mM and temperature 37.5C,). Parameters from Dash and Bassingthwaighte 2004. These are such that P50 for Hb-O2 saturation is 26 mmHg when RBC pH is 7.4 and pCO2 is 40 mmHg. The model is accurate through the physiological range of PO2s above 20 mmHg. Solutions are steady-state, calculated algebraically. The program is set to find saturation at each PCO2 from 0 to 100 mmHg.
• Hill model: The Hill Equation assumes instantaneous equilibrative binding of oxygen to Hb, but if there is delay due to diffusion or a membrane barrier, then the reaction is slowed. Antonini and Brunori (1971) and Frauenfelder (Austin et al 1975; Mourant et al 1993) showed that the rebinding of O2 to Hb involved a family of rate constants (including a fractal scaling region) and the the reaction was complete in less than 50 msec.
• AV Hill's empirical description of the hemoglobin-oxygen dissociation curve was based on data before the van Slyke apparatus for measuring the content of O2 in blood equilibrated with air at known PO2 and PCO2 was developed. The simplicity of the equation led to its wide utility, even though it is too low at saturations below 30% (a region not often visited physiologically). Other models, Adair's, Severinghaus', etc. offer improvements over this two parameter power law relationship.
• Adair model: Hb-O2 sauration curves using parameter values for succesive site affinities at Hb's 4 sites and accounting for their cooperativity. (Adair, 1925). Solutions are steady-state, calculated algebraically. The program is set to find saturation at each PO2 from 0 to 100 mmHg.
• CO2 model: Hb-CO2 sauration curves showing Haldane effect (higher O2 reducing the affinity of Hb for CO2, Lower pH does similarly). (DPG is 4.65 mM and temperature 37.5C,). Parameters from Dash and Bassingthwaighte 2004. These are such that P50 for Hb-O2 saturation is 26 mmHg when RBC pH is 7.4 and pCO2 is 40 mmHg. The model is accurate through the physiological range of PO2s above 20 mmHg. Solutions are steady-state, calculated algebraically. The program is set to find saturation at each PCO2 from 0 to 100 mmHg.
• Blood O2 model: Calculate the Oxygen Content of Blood. Based on Adair and Hill research.

Equations

Adair GS. The hemoglobin system. VI. The oxygen dissociation curve of hemoglobin. J Biol
Chem 63: 529-545, 1925.

Hill AV. The possible effects of the aggregation of the molecules of haemoglobin on its
dissociation curves. J Physiol 40: iv-vii, 1910

Hill R. Oxygen dissociation curves of muscle hemoglobin. Proc Roy Soc Lond B
120: 472-480, 1936.

Roughton FJW, Deland EC, Kernohan JC, and Severinghaus JW. Some recent studies of the
oxyhemoglobin dissociation curve of human blood under physiological conditions and the
fitting of the Adair equation to the standard curve. In: Oxygen Affinity of Hemoglobin and
Red Cell Acid Base Status. Proceedings of the Alfred Benzon Symposium IV Held at the
Premises of the Royal Danish Academy of Sciences and Letters, Copenhagen 17-22 May,
1971, edited by Rorth M and Astrup P. Copenhagen: Munksgaard, 1972, p. 73-81.

Winslow RM, Swenberg M-L, Berger RL, Shrager RI, Luzzana M, Samaja M,and
Rossi-Bernardi L. Oxygen equilibrium curve of normal human blood and its evaluation by
Adair's equation. J Biol Chem 252: 2331-2337, 1977.