The Validity of PO₂ Measurement in Capillary Blood as a Substitute for Arterial PO₂

Abstract

PO₂ in capillary blood was compared with arterial PO₂ under different conditions.

PO₂ in capillary blood from the hyperemic earlobe at rest and during exercise compares favorably with arterial PO₂, while discrepancy is rather large when capillary blood at rest is sampled from the warmed finger-tip. For PCO₂, good accordance was found regardless of the site of sampling.

In circulatory collapse, PO₂ in capillary blood does not accurately reflect arterial PO₂, even if sampled at the earlobe.

At oxygen tensions above 200 mm Hg accordance is very poor and the capillary method is thus unsuitable for determining true anatomic shunt.

Key Words:

• Blood circulation
• blood gas analysis
• capillary blood
• carbon dioxide tension
• hyperemia
• oxygen tension