pO₂
Arterial oxygen tension

Definition
pO₂ is the oxygen partial pressure (or tension) in a gas phase in equilibrium with the blood. High and low pO₂ values of arterial blood indicate hyperoxemia and hypoxemia, respectively. The analyzer symbol may be pO₂. The systematic symbol for arterial oxygen tension is pO₂(a); if mixed venous blood is analyzed, the corresponding systematic symbol is pO₂().

What does pO₂ tell you
The arterial oxygen tension pO₂(a) is an indicator of the oxygen uptake in the lungs.

Reference ranges
pO₂(a) reference range (adult): 83-108 mmHg (11.1-14.4 kPa); however, the reference range for adults also declines with age.
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Clinical interpretation
Normal pO₂:
A normal pO₂, while breathing room air, indicates an adequate pulmonary oxygen uptake.

High pO₂ (hyperoxemia):
High pO₂ leads to cellular hyperoxia and may be toxic, if sustained; unless a high level is specifically desired, inspiratory oxygen fraction should be reduced to normalize pO₂.

Low pO₂ (hypoxemia):
If pO₂ is too low, it may signify an inadequacy of the oxygen uptake from the lungs. Pulmonary and ventilatory status (i.e., chest radiograph, FShunt, pCO₂, pulmonary function test) should be reviewed; increasing the FO₂(I) and/or optimizing ventilator settings may be indicated along with, if possible, specific treatment of the pulmonary or cardiac changes causing the hypoxemia.

Be aware of the risk of preanalytical errors (air bubbles, storage) on pO₂ values.

For more information, go to Preanalytical considerations.