Normal PO₂ values
May 22, 2022
Source: Cainiu Health
Dr. Tian Hongbo
Introduction
PaO₂, or partial pressure of arterial oxygen, normally ranges from 95 to 100 mmHg. A PaO₂ below 95 mmHg typically indicates varying degrees of hypoxia in the patient. Clinically, hypoxemia is diagnosed when the patient is breathing room air (20.9% oxygen) and the arterial oxygen partial pressure falls below 60 mmHg. A PaO₂ below 60 mmHg suggests hypoxemia, which may cause dizziness.
PO2 generally refers to the partial pressure of oxygen in arterial blood, with a normal range of 95–100 mmHg.
The partial pressure of oxygen (PO2) in blood reflects the tension exerted by oxygen molecules physically dissolved in the blood—also termed “oxygen tension.” Values below the normal range may cause symptoms such as dizziness, cyanosis (bluish discoloration) of the lips, and tachycardia. An arterial PO2 < 95 mmHg typically indicates varying degrees of hypoxia; a value < 60 mmHg signifies hypoxemia, which can manifest clinically as dizziness, lip cyanosis, and tachycardia.
Elevated blood PO2 is not typical; however, elevated hemoglobin concentration, red blood cell count, and hematocrit—often collectively referred to as “polycythemia”—may occur. Causes include relative polycythemia due to reduced plasma volume, secondary polycythemia resulting from chronic tissue hypoxia, and primary (idiopathic) polycythemia vera. For arterial blood gas analysis, arterial blood is typically drawn from the radial, brachial, or femoral artery. If venous sampling is required, the forearm must be immersed in water at 45°C for 20 minutes to arterialize the venous blood.
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