Related Experiment Video
Updated: May 5, 2026
Primary Outcome Assessment in a Pig Model of Acute Myocardial Infarction
Published on: October 14, 2016
Measurement of cardiac output in man with a nonrecirculating indicator
Insights
Constant-rate injection of hydrogen (H2) offers a reliable method for measuring cardiac output. This nonrecirculating indicator technique provides reproducible results and is advantageous for repeated measurements.
Area of Science:
- Cardiovascular Physiology
- Diagnostic Medical Technology
Background:
- Accurate measurement of cardiac output is crucial for assessing cardiovascular function.
- Conventional indicator dilution methods can be affected by indicator recirculation.
- There is a need for reliable, reproducible methods for serial cardiac output determinations.
Purpose of the Study:
- To evaluate the utility of constant-rate injection of hydrogen (H2) as a nonrecirculating indicator for measuring cardiac output in humans.
- To assess the reproducibility and accuracy of the H2 method compared to established techniques.
Main Methods:
- Constant-rate injection of dissolved H2 into the systemic venous circulation or left heart.
- Chromatographic measurement of H2 concentration in pulmonary or systemic arterial blood.
- Direct measurement of intrapulmonary H2 elimination.
- Comparison with direct Fick and dye dilution methods.
Main Results:
- Intrapulmonary H2 elimination averaged 98 +/-1.5% (SD).
- Reproducibility of H2 cardiac output measurements showed coefficients of variation averaging 3.4 +/-2.0%.
- H2 outputs correlated well with Fick (106 +/-4% of Fick) and dye dilution methods (106 +/-3% in low regurgitation, 91 +/-4% in moderate-to-severe regurgitation).
Conclusions:
- Constant-rate H2 injection is a reproducible and accurate method for measuring cardiac output.
- The H2 technique is advantageous for rapid, repeated measurements and in situations with potential indicator recirculation.
- This method allows for the quantitation of small changes in cardiac output.
Abstract:
The present investigation was undertaken to evaluate the utility of constant-rate injection of a nonrecirculating indicator (H(2)) for the measurement of cardiac output in man. 42 patients were studied during cardiac catheterization and 8 during acute complications of arteriosclerotic heart disease, including acute myocardial infarction. Pulmonary (or systemic) arterial H(2) concentration was measured chromatographically from 2.0 ml blood samples drawn during constant-rate injection of dissolved H(2) into the systemic venous circulation (or left heart). The chromatograph was a thermal conductivity unit housed in a constant-temperature water bath to achieve an improved signal-to-noise ratio. Intrapulmonary H(2) elimination from mixed venous blood was measured directly in 14 patients and averaged 98 +/-1.5% (SD). Reproducibility of output measurements was evaluated using triplicate determinations obtained over 45-60 sec in 25 consecutive patients. Coefficients of variation (SD/Mean x 100) averaged 3.4 +/-2.0%, making it possible to evaluate relatively small changes in measured output with conventional statistical tests. Individual measurements could be repeated at 10-15 sec intervals. Comparisons of H(2) and direct Fick measurements were made in 14 patients; H(2) outputs averaged 106 +/-4% (SEM) of Fick outputs (P > 0.1). Comparisons of H(2) and dye dilution measurements were performed in an additional 24 patients. Seven had angiographically-negligible valvular regurgitation and dye outputs averaged 106 +/-3% of H(2) outputs (P > 0.1). 17 had moderate-to-severe regurigation and dye outputs averaged 91 +/-4% of H(2) outputs (P < 0.05), suggesting a small but systematic error due to undetected recirculation of dye. The H(2) technique appears advantageous for rapidly repeated determinations of output, for quantitation of small changes in output, and for situations in which recirculation of conventional indicators is a potentially significant problem.
More Related Videos
08:01Semi-Minimal Invasive Method to Induce Myocardial Infarction in Rats and the Assessment of Cardiac Function by an Isolated Working Heart System
Published on: June 11, 2020
06:10Author Spotlight: Assessment of Cardiac Output Calculation by Thermodilution in Pigs for Effective Perfusion Flow During EVLP
Published on: June 28, 2024
Related Concept Videos
01:05Pulse
Pulse Rate and its Significance
Pulse rate, often measured in beats per minute (bpm), reflects the heart rate (HR), which is influenced by numerous factors such as stress, physical activity, and hormonal changes. A normal resting adult pulse rate falls...
01:11Cardiac Output and Stroke Volume
In an average resting adult male, the typical cardiac...
01:17Exercise and Cardiac Output
Sustained exercise increases the muscles' oxygen demand, which can be...
01:18Physiology of the Heart: The Cardiac Cycle
Diastole: The Relaxation Phase
During diastole, all four heart chambers relax. The atrioventricular (AV) valves open, and the semilunar valves close. This phase sees the lowest chamber pressures, promoting ventricular filling. Venous blood enters the heart through the...
01:19Cardiac Output I:Effect of Heart Rate on Cardiac Output
Cardiac output (CO) refers to the total amount of blood ejected by one of the ventricles in liters per minute (L/min). In a resting adult, CO ranges from 5 to 6 L/min, adjusting according to the body's metabolic requirements.
Effect of Heart Rate on Cardiac Output
Cardiac output adapts to metabolic demands during stress, physical activity, or illness. The autonomic nervous system regulates heart rate via the sinoatrial node. The parasympathetic nervous system decreases heart...
01:22Cardiac Output II: Effect of Stroke Volume on Cardiac Output
Preload
Preload refers to the initial elongation of the cardiac myocytes before contraction and is related to the volume of blood filling the heart at the end of diastole, or end-diastolic volume. The...