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Arterial Oxygen Content (CaO₂)

Oxygen carried by haemoglobin plus dissolved oxygen.

For healthcare professionalsRespiratoryv1.0.1

For healthcare professionals / clinical use. Not a self-diagnosis tool.

Your measurements

%

Calculated on your device. Nothing is sent to a server.

Your result will appear here

Enter your measurements, then press Calculate.

Methodology

Oxygen content equation

CaO₂ = 1.34 × Hb × SaO₂ + 0.003 × PaO₂

1.34 mL of O₂ binds each gram of haemoglobin; 0.003 mL/dL dissolves per mmHg of PaO₂.

Who it is for
Adults with haemoglobin, SaO₂ and PaO₂ values.
Version
1.0.1

How this calculator works

Where the formula comes from

  • Oxygen content is the total oxygen in blood, chemically bound to haemoglobin plus physically dissolved.[1]

The inputs

  • Oxygen carried in plasma is small (about 0.3 mL per 100 mL); each gram of haemoglobin binds up to about 1.39 mL of oxygen.[2]

Where accuracy falls (published evidence)

  • Anaemia lowers oxygen content while PaO₂ and saturation stay normal; carbon monoxide or methaemoglobin lowers saturation and content with a normal PaO₂.[1]

Sources

  1. Zander R. The oxygen status of arterial human blood. Scand J Clin Lab Invest Suppl. 1990;203:187–196. doi:10.3109/00365519009087509
  2. Otto JM, Montgomery HE, Richards T. Haemoglobin concentration and mass as determinants of exercise performance and of surgical outcome. Extrem Physiol Med. 2013;2(1):33. doi:10.1186/2046-7648-2-33

Compiled from the published sources above. Every statement was agreed independently by three AI research tools (Claude, ChatGPT, DeepSeek) and its source verified in PubMed or Crossref by the Hakeemly editorial team. Not reviewed by a doctor unless stated. Agreed on

Worked example: how to calculate oxygen content

Inputs

Haemoglobin
15 g/dL
SaO₂
98 %
PaO₂ (arterial oxygen)
100 mmHg

Result

CaO₂
20 mL O₂/dL

Calculation:

1.34×15×0.98 + 0.3 = 19.70 + 0.3 = 20.0

An illustration with sample values, worked out with the same method the tool above uses.

Limitations

  • Published values for oxygen bound per gram of haemoglobin differ; 1.39 mL has been reported (Otto 2013), and this calculator uses 1.34. Oxygen saturation and PaO₂ stay normal in anaemia even though content falls (Zander 1990).

References

  1. West JB, Luks AM. West's Respiratory Physiology: The Essentials. 11th ed. Philadelphia: Wolters Kluwer; 2021.
  2. Zander R. The oxygen status of arterial human blood. Scand J Clin Lab Invest Suppl. 1990;203:187–196. doi:10.3109/00365519009087509
  3. Otto JM, Montgomery HE, Richards T. Haemoglobin concentration and mass as determinants of exercise performance and of surgical outcome. Extrem Physiol Med. 2013;2(1):33. doi:10.1186/2046-7648-2-33

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