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Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses
Published on: October 21, 2016
Comparative study of calculated and measured total carbon dioxide
Anchalee Chittamma1, Somlak Vanavanan
1Division of Clinical Chemistry, Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand. anchalee_chit@yahoo.com
Clinical Chemistry and Laboratory Medicine
|August 1, 2007
Summary
Calculated total carbon dioxide (TCO2) from blood gas analysis shows good agreement with directly measured TCO2. This method can help assess acid-base balance, but caution is advised in critically ill patients.
Area of Science:
- Clinical Chemistry
- Medical Diagnostics
- Acid-Base Balance
Background:
- Total carbon dioxide (TCO2) can be calculated using pH and pCO2 via the Henderson-Hasselbalch equation or measured directly.
- Accurate TCO2 assessment is crucial for diagnosing and managing acid-base disturbances.
Purpose of the Study:
- To evaluate the agreement between calculated TCO2 and directly measured TCO2.
- To determine the reliability of calculated TCO2 for clinical use in acid-base assessment.
Main Methods:
- Agreement was assessed in 74 blood samples comparing calculated TCO2 (from pH/pCO2 on Nova Stat Profile Xpress) with measured TCO2 (on Dimension RxL).
- Statistical analyses included Deming regression, correlation coefficients, Bland-Altman bias analysis, and Student's t-test.
Main Results:
- A high correlation (r=0.97) was observed between calculated and measured TCO2.
- Deming regression showed a slope near 1 (0.96) and a positive intercept (2.86 mmol/L).
- Mean bias was 1.94 mmol/L, with most differences within the 95% limits of agreement (-1.45 to 5.33 mmol/L).
Conclusions:
- Calculated TCO2 using blood gas analysis demonstrates good agreement with measured TCO2.
- This method is suitable for assessing acid-base imbalance, with a caveat for critically ill patients.
- Clinicians should exercise caution when interpreting calculated TCO2 in critically ill individuals.
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