Determination of Rebreathing Oxygen Consumption and Derivation of Oxygen Delivery in Intubated Mongrel Dogs after Phlebotomy and Isoproterenol Infusion

ABSTRACT This study attempted to determine the correlation between oxygen consumption (VO 2 ), pulmonary-capillary blood flow (Q EPC ) and oxygen delivery (DO 2 ) by rebreathing and invasive techniques obtained over a range of hemoglobin concentration and cardiac output. Twenty mongrel dogs were instrumented with central arterial and venous catheters to determine DO 2 by thermodilution cardiac output and standard formulas. The animals were administered isoproterenol in doses that increased DO 2 and subsequently were serially phlebotomized by 30%, 40%, and 50% to decrease DO 2 . All animals were studied using a rebreathing technique to determine noninvasively VO 2 , Q EPC , and DO 2 . Sixteen dogs completed the experimental protocol. A correlation analysis was carried out for VO 2 , Q EPC , and DO 2 obtained by the rebreathing and invasive methods. Thermodilution cardiac output increased from 3.91 ± 1.77 L/min at baseline to 8.19 ± 2.50 L/min during isoproterenol infusion. Hemoglobin varied from 12.21 ± 1.26 gm% at baseline to 5.21 ± 1.36 g% at 50% phlebotomy. Over this range of conditions, significant correlations were obtained between rebreathing VO 2 and invasive VO 2 (r = 0.80, p  EPC and invasive Q EPC (r = 0.79, p  2 and invasive DO 2 (r = 0.82 p  These data demonstrate that the rebreathing technique can be used to monitor oxygen metabolism over wide ranges of DO 2 .