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Can changes in end-tidal PCO2 measure changes in cardiac output?
1Department of Anesthesia and Critical Care, University of Chicago, IL 60637.
Anesthesia and Analgesia
|December 1, 1991
Summary
Changes in end-tidal carbon dioxide tension (PETCO2) closely reflect changes in cardiac output (QT). This study in dogs suggests PETCO2 may serve as a noninvasive monitor for QT during critical care.
Area of Science:
- Cardiovascular Physiology
- Respiratory Physiology
- Anesthesiology
Background:
- End-tidal carbon dioxide tension (PETCO2) increases indicate improved cardiac output (QT) during cardiopulmonary resuscitation.
- The relationship between dynamic changes in QT and PETCO2 requires further investigation.
Purpose of the Study:
- To test the hypothesis that changes in QT can be reliably monitored by changes in PETCO2.
- To investigate the physiological mechanisms linking QT and PETCO2 variations.
Main Methods:
- Vena cava balloons were used to decrease QT in pentobarbital-anesthetized dogs.
- QT was measured using pulmonary thermodulation.
- PETCO2 was continuously monitored using infrared capnometry.
Main Results:
- A direct linear correlation was observed between percent decreases in PETCO2 and percent decreases in QT (R2 = 0.89, P < 0.001).
- Reduced CO2 delivery to the lungs and increased alveolar dead space contributed to decreased PETCO2 during lower QT.
- PETCO2 levels gradually returned towards baseline due to peripheral CO2 accumulation during sustained QT reduction.
Conclusions:
- The strong linear relationship between PETCO2 and QT in this animal model supports further clinical research.
- PETCO2 shows potential as a noninvasive, continuous monitor for QT fluctuations in anesthesia and intensive care settings.