Arterial oxygen content is the total amount of oxygen actually carried in each deciliter of arterial blood — combining hemoglobin-bound and dissolved oxygen — and explains why hemoglobin matters as much as PaO₂ for oxygen delivery.
| Term | Meaning |
|---|---|
| 1.34 | mL O₂ carried per gram of hemoglobin |
| Hgb | Hemoglobin concentration (g/dL) |
| SaO₂ | Arterial saturation (as a fraction) |
| 0.003 × PaO₂ | Dissolved oxygen |
Normal arterial oxygen content.
Mildly reduced — often mild anemia or desaturation.
Moderately reduced content.
Severely reduced — oxygen delivery is threatened.
Given: Hgb 15 g/dL, SaO₂ 98%, PaO₂ 90 mmHg.
19.70.27The vast majority of blood oxygen is bound to hemoglobin; only a trace is dissolved.
Severe anemia lowers CaO₂ even with a normal PaO₂ and SaO₂, because hemoglobin carries the vast majority of the blood's oxygen. Fewer red cells means less oxygen delivered, regardless of the pressure reading.
Roughly 16–20 mL of oxygen per deciliter of arterial blood in a healthy adult.
Only about 0.003 mL of oxygen dissolves per dL per mmHg of PaO₂, so even a PaO₂ of 100 contributes only ~0.3 mL/dL — a tiny fraction of the total compared with hemoglobin-bound oxygen.
SaO₂ is the percentage of hemoglobin binding sites filled with oxygen; CaO₂ is the actual total amount of oxygen per deciliter, which also depends on how much hemoglobin there is.