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Arterialized capillary blood gases in exercise studies.
Medicine and Science in Sports
|January 1, 1975
Summary
Arterialized capillary blood offers a viable alternative to arterial blood for measuring blood gases and pH, especially during exercise. Accuracy is highest for pH and lowest for PO2, but PCO2 and PO2 are precise enough for physiological calculations.
Area of Science:
- Physiology
- Respiratory Medicine
- Clinical Chemistry
Background:
- Arterial blood gas analysis is crucial for assessing respiratory function.
- Arterialized capillary blood sampling offers a less invasive alternative.
- The reliability of capillary blood for gas exchange parameters during rest and exercise requires further validation.
Purpose of the Study:
- To compare partial pressures of carbon dioxide (PCO2), oxygen (PO2), and pH in arterial and arterialized earlobe capillary blood.
- To evaluate the accuracy of capillary blood gas measurements for calculating cardiac output and dead space:tidal volume ratio during exercise.
- To determine the conditions under which capillary blood can reliably substitute for arterial blood.
Main Methods:
- Simultaneous collection of arterial and earlobe capillary blood samples from 13 patients at rest and during submaximal exercise.
- Measurement of PCO2, PO2, and pH in both sample types.
- Calculation of cardiac output (indirect Fick method) and dead space:tidal volume (VD/VT) ratio using both arterial and capillary PCO2.
Main Results:
- Capillary PCO2 was slightly lower than arterial PCO2, with greater variation than duplicate capillary samples.
- Capillary PO2 was higher than arterial PO2, with significant variation.
- Using capillary PCO2 for calculations led to systematic overestimation of cardiac output and underestimation of VD/VT ratio.
- Accuracy was highest for pH and lowest for PO2, but PCO2 and PO2 measurements were sufficiently precise for physiological calculations.
Conclusions:
- Arterialized capillary blood is an acceptable substitute for arterial blood for blood gas and pH measurements, provided adequate blood flow.
- Capillary blood gas measurements are sufficiently precise for calculating cardiac output, VD/VT ratio, and other respiratory parameters during exercise.
- While PO2 measurements show the most variability, capillary sampling offers a practical alternative for routine clinical assessment.