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Cardiac output estimated noninvasively from oxygen uptake during exercise
W W Stringer1, J E Hansen, K Wasserman
1Division of Respiratory and Critical Care Physiology and Medicine, Harbor-UCLA Medical Center, Torrance 90509, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|March 1, 1997
Summary
Cardiac output (CO) and stroke volume can be estimated during exercise using oxygen uptake (Vo2) measurements. A predictable linear relationship was found for the arteriovenous oxygen content difference, enabling accurate CO estimation.
Area of Science:
- Cardiopulmonary exercise physiology
- Noninvasive cardiovascular diagnostics
Background:
- Gas-exchange measurements during cardiopulmonary exercise testing provide noninvasive oxygen uptake (Vo2) data.
- Vo2 is a product of cardiac output (CO) and the arteriovenous oxygen content difference [C(a-vDo2)].
- Theoretically, CO and stroke volume could be estimated if C(a-vDo2) predictably increased with Vo2 during exercise.
Purpose of the Study:
- To investigate the behavior of C(a-vDo2) during progressively increasing ramp cycle ergometry exercise.
- To determine if C(a-vDo2) increases predictably as a function of % maximum Vo2 (Vo2max).
- To assess the feasibility of estimating CO and stroke volume noninvasively.
Main Methods:
- Five healthy subjects performed 10 exercise tests to exhaustion.
- Arterial and mixed venous blood samples were collected and analyzed for blood gases and hemoglobin concentration.
- Linear regression analysis was used to model the relationship between C(a-vDo2) and % Vo2max.
Main Results:
- C(a-vDo2) could be estimated using a linear regression equation: C(a-vDo2) = 5.72 + 0.105 x % Vo2max (r = 0.94).
- Estimated CO correlated well with directly measured CO (r = 0.96).
- The coefficient of variation for estimated CO was low (7-9%) between the lactic acidosis threshold and peak Vo2.
Conclusions:
- Cardiac output and stroke volume can be estimated during progressive exercise testing from measured Vo2.
- The derived linear regression equation provides a reliable estimate of C(a-vDo2).
- This method is applicable to both normal subjects and patients with congestive heart failure.