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Estimation of arterial PCO2 in the elderly
C M St Croix1, D A Cunningham, J M Kowalchuk
1Centre for Activity and Ageing, Lawson Research Institute, University of Western Ontario, London, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|December 1, 1995
Summary
Arterial PCO2 (PaCO2) was compared to indirect estimates in elderly men. Arterialized venous PCO2 (PavCO2) showed the closest agreement with actual PaCO2 at rest and during exercise.
Area of Science:
- Physiology
- Respiratory Medicine
- Gerontology
Background:
- Accurate measurement of arterial PCO2 (PaCO2) is crucial for assessing respiratory function.
- Noninvasive methods for estimating PaCO2 are desirable, especially in elderly populations.
Purpose of the Study:
- To compare direct radial arterial PCO2 measurements with various indirect estimation methods in elderly men.
- To evaluate the accuracy of these methods at rest and during exercise.
Main Methods:
- Direct radial arterial PCO2 (PaCO2) measurement.
- Indirect estimation methods included arterialized venous PCO2 (PavCO2), end-tidal PCO2, mean alveolar PCO2, and a formula incorporating end-tidal PCO2 and tidal volume.
- Measurements were taken in six elderly men at rest and during cycle ergometry (25 and 50 W) under various breathing conditions.
Main Results:
- Arterialized venous PCO2 (PavCO2) demonstrated the closest agreement with direct PaCO2 measurements at rest and during exercise.
- All noninvasive methods using respired gases overestimated PaCO2 at rest.
- The Jones et al. formula provided the closest noninvasive estimate to PaCO2 during exercise.
Conclusions:
- Arterialized venous PCO2 (PavCO2) is the most accurate indirect method for estimating PaCO2 in elderly men at rest and during exercise.
- Noninvasive techniques using respired gases have limitations, particularly at rest.