M. Nakamura et al., Mixed venous oxygen saturation as a promising parameter for physiologic control of total artificial heart, ASAIO J, 46(6), 2000, pp. 761-766
Mixed venous oxygen saturation (SvO(2)) has been proposed as one of the sui
table parameters for physiologic control of a total artificial heart (TAH).
To establish the practical application of SvO(2), we investigated the resp
onse of cardiac output (CO) and SvO(2) to step-loaded exercise. A normal ca
lf was surgically equipped with an ultrasonic flowmeter probe and an oximet
ry catheter in the pulmonary artery to measure CO and SvO(2), respectively.
Three stage step treadmill exercise tests (1, 2, and 4 km/h) were performe
d three times. While CO increased from 8.9 L/min at preexercise level to 9.
7, 10.2 and 11.4 L/min at 1, 2, and 4 km/h, respectively, SvO(2) decreased
from 59.6% to 56.8, 55.3, and 52.2%, respectively. There existed a linear c
orrelation between the magnitude of changes in CO and SvO(2). CO and SvO(2)
exhibited a similar course of change, expressing an inverted exponential c
urve. The time constant of SvO(2) was from 19 to 35 seconds, whereas that o
f CO was from 21 to 39 seconds. We conclude that SvO(2) changes in close as
sociation with CO during exercise and has good potential to be a parameter
for physiologic control of a TAH, by reflecting the recipient's CO demand w
ithout conspicuous time delay.