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Differences in PO2 and PCO2 between arterial and arterialized earlobe samples
A Sauty1, C Uldry, L F Debétaz
1Division de Pneumologie, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
The European Respiratory Journal
|February 1, 1996
Summary
Arterialized earlobe blood is not a reliable measure for oxygen levels in adult patients. While carbon dioxide measurements show good agreement, oxygen partial pressure (PO2) readings from the earlobe are often lower than arterial values.
Area of Science:
- Medical Diagnostics
- Respiratory Physiology
Background:
- Arterialized earlobe blood sampling is a commonly used, safe method for assessing blood gases.
- Its adequacy for monitoring gas exchange in critically ill patients has been previously suggested.
Purpose of the Study:
- To prospectively evaluate the validity of using arterialized earlobe blood samples to assess gas exchange.
- To compare oxygen partial pressure (PO2) and carbon dioxide partial pressure (PCO2) values from earlobe and radial artery samples.
Main Methods:
- A prospective study involving 115 adult patients.
- Simultaneous blood samples were drawn from the arterialized earlobe and radial artery.
- Partial pressures of oxygen (PO2) and carbon dioxide (PCO2) were measured using blood gas electrodes.
Main Results:
- High correlation coefficients were observed for both PO2 (0.928) and PCO2 (0.957).
- Despite strong correlation, wide limits of agreement were found for PO2, with earlobe values typically lower than arterial.
- PCO2 measurements demonstrated smaller errors and limits of agreement compared to PO2.
Conclusions:
- Arterialized earlobe blood PO2 is not a reliable indicator of arterial PO2 in adult patients.
- While PCO2 measurements show acceptable agreement, PO2 measurements from the earlobe should be interpreted with caution, especially within the normal arterial range.