8 



Scientific Proceedings (109). 



D vol. per cent. (Amount by which the carbon-dioxido com- 

 bining capacity of blood is increased as a result of the effect 

 oxygen unsaturation). 



As applied to the figures given by Haldane 1 and by Joffe 2 

 it shows an error of only 10 per cent, between C0 2 - tensions of 

 30 and 70 mm. inclusive. This equation has been employed in 

 the calculation of arterial and venous carbon dioxid tension. 

 Although the differences in C0 2 tension between arterial and 

 venous blood are greater and more variable than the results of 

 indirect methods have led us to believe, the slope of the dissocia- 

 tion curve and the effect of oxygen combined prevent any change 

 in the hydrogen-ion concentration. The P H of venous blood 

 as calculated from the H 2 C0 3 /BHC0 3 ratio is practically the 

 same as that of arterial blood. 



In cardiac dyspnea the difference between alveolar and arterial 

 CO2- tension was always much greater than normal, varying from 

 13 to 19 mm. Hg. This indicates some impairment of the mech- 

 anism for the elimination of carbon dioxid in the lungs: either 

 that parts of the lungs are unaerated or that they are imperfectly 

 ventilated. The arterial P H was once absolutely diminished and 

 once relatively diminished, indicating the presence of a true carbon 

 dioxid retention. Most of the patients studied did not recover 

 compensation, but in one case the carbon dioxid retention disap- 

 peared completely and the arterial P H and the relation of arterial 

 to alveolar carbon dioxid tension, returned to normal. The 

 difference between arterial and venous carbon dioxid content 

 and arterial and venous carbon dioxid tension was only occasionally 

 greater than normal. A retarded circulation rate is therefore 

 not a necessary concomitant of cardiac decompensation with 

 dyspnea. The venous and arterial P H were practically identical 

 even in those cases with an increased difference between arterial 

 and venous carbon dioxid tension because of the greater oxygen- 

 unsaturation of the venous blood. 



In severe anemia not only is the dissociation curve higher 

 and more nearly horizontal than normal at CCVtensions that 

 exist in the body, but the compensating effect of oxygen is greatly 



1 Christiansen, Douglas and Haldane, Journ. Physiol., 1914, xliii, 244. 



2 Joffe, Poulton, Poulton and Poulton, Journ. Physiol., 1920, liv, 129. 



