EFFECT OF AN INCREASE IN HBO2 AFFINITY ON THE CALCULATED CAPILLARY RECRUITMENT OF AN ISOLATED RAT-HEART

The effect of an increase in Hb O2 affinity on myocardial O2 delivery was studied in a blood perfused working rat heart preparation. In a 1st series of experiments P50 (PO2 [O2 partial pressure] for which saturation is 50%) was lowered by use of CO. The heart was alternatively perfused with the blood sample of P50 = 32 mm Hg and the blood sample of P50 = 17 mm Hg. O2 capacity of both samples was kept the same by appropriate hemodilution. In a 2nd series of experiments change of P50 was obtained by the use of adult human erythrocytes containing Hb creteil with a P50 of 13.6 mm Hg. As P50 decreased from 25 to 10 mm Hg, coronary sinus PO2 (PcsO2) diminished from 26 .+-. 2 to 18 .+-. 2 mm Hg (-29 .+-. 2%), coronary sinus O2 content (CcsO2) increased by 15 .+-. 3%, myocardial O2 consumption did not change significantly. The percentage of increase of coronary flow was 23 .+-. 4%. Analysis of these results with a simple mathematical model of O2 delivery suggests that increase in HbO2 affinity is corrected by a simultaneous increase in coronary flow and capillary recruitment.