The International Journal of Artificial Organs / Vol. 16/ no. 3. 1993/ pp. 135-140 Artificial Heart and Cardiac Assist Devices Measurement of oxygen consumption and arterial-venous oxygen saturation following total artificial heart implantation P.O. ROBISON 1 , G.M. PANTALOS 1 , J. W. LONG 1 Jr, R.S. BLlSS 1 , D.K. PRICE 1 , S.D. EVERETT 1 , P. GOLoMAN 1 , I. GOLoENBERG 2 , o.B. OLSEN 1 1 Artificial Heart Research Laboratory, Institute for Biomedical Engineering, University of Utah, Salt Lake City, Utah 2 Minneapolis Heart Institute Foundation, Minneapolis, Minnesota - USA ABSTRACT: Current algorithms for control of the total artificial heart are directed at maintaining hemodynamic homeostasis. Future control systems will also need to modify cardiac output in response to metabolic needs. This study was undertaken to evaluate oxygen metabolism monitoring as an indicator of the adequacy of organ and tissue perfusion. Following recovery from implantation of the Utah-100 pneumatic total artificial hearts, five calves (85 to 95 kg) underwent placement of fiberoptic oxymetry catheters to determine mixed venous and arterial oxygen saturations. By continuously measuring oxygen consumption with a gas analyzer, oxygen utilization and delivery were determined. In the awake calves, at-rest cardiac output was varied to produce hyperperfused and hypoperfused conditions while the adequacy of tissue perfusion was assessed with continuous mixed venous oxymetry and confirmed with serum lactate (Lact) levels. Inadequate tissue perfusion (Lact > 1.0 mmol/L) was evidenced by a mixed venous oxygen saturation <40%, oxygen delivery of < 200.0 mittiliterstminutelmt), and oxygen delivery to utilization ratio of < 1.8 during the hypoperfusion conditions of the experiment. By accounting for oxygen consumption, the ratio of oxygen delivery to oxygen utilization was predictive of the adequacy of tissue perfusion. These results suggest that continuous oxygen metabolism monitoring may be useful as a physiologic control modifier to maintain total artificial heart output sufficient to meet physiologic needs, while avoiding hyperperfusion, unnecessary wear and deterioration of the implanted device due to excessive heart rates. (Int J Artif Organs 1993; 16: 135-40) KEY WORDS: Total artificial heart, Oxygen consumption, Oxygen metabolism, Metabolic control INTRODUCTION Development of a totally implantable artificial heart (TIAH) requires a simple yet reliable blood pumping system, and a control scheme to assure that the patient's physiologic needs are met. Current control schemes are based on the assumption that the heart is a simple pump that should deliver blood at some specified "normal" rate (1). This view of the heart neglects the basic function of the circulatory system, that is, to deliver oxygen and nutrients to the tissues and clearing cellular excreta from the normal pro- cesses of metabolism. Although hemodynamic data are vital in a basic control scheme, sensors are now available that will allow the measurement of many important nutrients required by the body; this infor- mation could be used to modify the cardiac output (CO) based on the ever-changing physiologic needs of the TIAH patient. Although complete physiologic feedback data would © by Wichtig Editore, 1993 0391-3988/135-06 $01.50/0