70. BLOOD O2 DISSOCIATION LINE CHARTS: MAN 



USE OF CHARTS: 



Changes in temperature and pHs (serum) alter the position but not the shape of the oxygen dissociation 

 curve. Dissociation curves for various values of pHs and temperature for man may be computed from the one 

 standard curve for normal human blood at 37°, pHs 7.4, by multiplying all the pO^ values by factors for tempera- 

 ture and pHs. The left-hand line gives factors for temperature, the next line factors for pHs. The two right-hand 

 line graphs give the standard oxygen dissociation curve in a form more easily read than the usual graph. The 

 computation is given by 



Pt, pH = P x ft " fpH 

 where Pj pH is the p02 at temperature t and pH, P is the p02 at 37°, pHs 7.4 for the same % saturation, given on 

 the standard curve, and ft and fpn are the multipliers obtained from the line charts. 



Examples of the use of these charts follow: 



1) Problem : Prepare a complete oxygen dissociation curve for 30°, pH 7.6. 



Method : The factor for 30° is 0.74, and for pH 7.6 is 0.80. Their product is 0.59. Multiply all p02 values in 



the standard curve by 0.59; i.e., for 50% saturation, pO^ in the new curve is 26.4 x 0.59 = 15.6 mm Hg. 



Z) Problem : Arterial blood taken during surgery had 88% saturation by Van Slyke manometric methods. pH was 

 7.56 at body temperature of 33.8°C. What is the pOz? 



Method : From the standard dissociation curve, right-hand line, at 88% saturation, pO^ = 57 mm Hg. The 

 factors are, for pH, 0.84 and for temperature, 0.87. pO^ = 57 x 0.84 x 0.87 = 41.6 mm Hg in the 

 patient. 



To convert tension to saturation, factors are used as dividers: 



3) Problem : Arterial blood from a febrile subject had a p02 of 73 mm Hg, determined at body temperature, 40°C, 

 using a Roughton Scholander syringe. pHs, corrected to 40°, was 6.98. What is the % saturation? 



Method: 



Factors are 1.14 for temperature, and 1.52 for pHs. 

 sociation curve, this equals 77% saturation. 



73 



1.14 X 1.52 



= 42.1 mm Hg. From the dis- 



4) Problem : Blood taken from a heart-lung by-pass machine was found to have a p02 by polarograph of 65 mm Hg 

 and pHs of 7.72, both having been measured at 37°. The blood in the machine was at 30°. What is 

 the % saturation, and the p02, in the machine? 



Method : Since the blood was warmed anaerobically to 37° for pHs and p02 measurement, its saturation was 

 unchanged, and the only correction needed to calculate saturation is that for pHs. This, for 7.72 is 

 65 



0.70. 



0.70 



= 93 mmHg, which from the dissociation curve reads 96.4% saturation. 



To find p02 at 30°, first the pHs at 30° must be computed from the whole blood pHs factor, -0.0147 

 units per degree [ l] . -7° x -0.0147 = +0.103. Inasmuch as pHs rises as temperature falls, 0.103 is 

 added to 7.72 ( = 7.82). The factor for pH 7.82 is 0.63 and for 30° is 0.74. 93 x 0.63 x 0.74 = 43.3 

 mm Hg p02 in the machine. A simpler method of correcting the p02 from 37° to 30° is given in the 

 line chart on page 62 (correction of p02 and PCO2 of blood in vitro for temperature changes). 



The standard dissociation curve, and the pHs and temperature factors are taken from curves published by 

 Dill and Forbes [ 2, 3] . Tensions at the high end of the curves were taken from Nahas, etal [4] . These are assumed 

 to be average curves, subject to some variation in normals and perhaps great variation in disease, particularly 

 diabetes and anemia. The chief reason for variation is failure of intracellular pHc, which actually determines the 

 affinity of hemoglobin for oxygen, to be constantly related to serum pHs. 



Contributor : Severinghaus, J. W. 



References: ( l) Rosenthal, T. B. 

 Physiol! 132:685, 1941. [3] Dill, 

 Research, Washington, 1944. [4] 



, J. Biol. Chem. 173:25, 1948. [2] Dill, D. B., and Forbes, W. H.. Am. J. 

 D. B., "Handbook of Respiratory Data in Aviation," Committee on Medical 

 Nahas, C. G.. Morgan. E. H.. and Wood. E. H., J. Appl. Physiol. 5:169,1952. 



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