DETERMINATION OF REBREATHING OXYGEN-CONSUMPTION AND DERIVATION OF OXYGEN DELIVERY IN INTUBATED MONGREL DOGS AFTER PHLEBOTOMY AND ISOPROTERENOL INFUSION

This study attempted to determine the correlation between oxygen consu mption (VO2), pulmonary-capillary blood flow (Q(EPC)), and oxygen deli very (DO2) by rebreathing and invasive techniques obtained over a rang e of hemoglobin concentration and cardiac output. Twenty mongrel dogs were instrumented with central arterial and venous catheters to determ ine DO2 by thermodilution cardiac output and standard formulas. The an imals were administered isoproterenol in doses that increased DO2 and subsequently were serially phlebotomized by 30%, 40%, and 50% to decre ase DO2. All animals were studied using a rebreathing technique to det ermine noninvasively VO2, Q(EPC), and DO2. Sixteen dogs completed the experimental protocol. A correlation analysis was carried out for VO2, Q(EPC), and DO2 obtained by the rebreathing and invasive methods. The rmodilution cardiac output increased from 3.91 +/- 1.77 L/min at basel ine to 8.19 +/- 2.50 L/min during isoproterenol infusion. Hemoglobin v aried from 12.21 +/- 1.26 gm% at baseline to 5.21 +/- 1.36 g% at 50% p hlebotomy. Over this range of conditions, significant correlations wer e obtained between rebreathing VO2 and invasive VO2 (r = 0.80, p < 0.0 001), rebreathing Q(EPC) and invasive Q(EPC) (r = 0.79, p < 0.0001), a nd rebreathing DO2 and invasive DO2 (r = 0.82 p < 0.0001). These data demonstrate that the rebreathing technique can be used to monitor oxyg en metabolism over wide ranges of DO2.