Cardiac output estimated non-invasively from oxygen uptake (o2)
during exercise.
Stringer, William W., James E. Hansen, and K. Wasserman.
Institution: Harbor-UCLA Medical Center, Division of Respiratory
and Critical, Care Physiology and Medicine, Torrance, CA 90509
APStracts 3:0508A, 1996.
Since gas exchange measurements during cardiopulmonary exercise
testing allow non-invasive measurement of oxygen uptake (O2), which
is equal to cardiac output (C.O.) x arterio-venous oxygen content
difference (C(a-v)O2), C.O. and stroke volume (SV) could
theoretically be estimated if the C(a-v)O2 increased in a predictable
fashion as a function of %O2 max during exercise. To investigate the
behavior of C(a-v)O2 during progressively increasing ramp pattern
cycle ergometry exercise, 5 healthy subjects performed 10 studies to
exhaustion while sampling arterial and mixed venous blood. Samples
were analyzed for blood gases (pH, PCO2, PO2) and oxyhemoglobin and
hemoglobin concentration with a Co-Oximeter. The C(a-v)O2 (ml/100ml)
could be estimated with a linear regression (C(a-v)O2 = 5.72 + 0.105
x %_eq V\d\ba7()\s\up9(.) __O2 max) (r = 0.94). The C.O. estimated
from the C(a-v)O2 using the above linear regression was well
correlated with the C.O. determined by the direct Fick Method
(r=0.96). The coefficient of variation (COV) of the estimated C.O.
was small (7-9 %) between the LAT and peak _eq V\d\ba7()\s\up9(.)
__O2. The behavior of C(a-v)O2, as related to peak _eq
V\d\ba7()\s\up9(.) __O2, was similar regardless of cardiac function
when compared to similar measurements from studies in the literature
performed in normal and congestive heart failure patients. In
summary, cardiac output and stroke volume can be estimated during
progressive work rate exercise testing from measured _eq
V\d\ba7()\s\up9(.) __O2 (in normal subjects and patients with CHF),
and the resultant linear regression equation provides a good estimate
of C(a-v)O2.
Received 22 July 1996; accepted in final form 24 October 1996.
APS Manuscript Number A693-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996