Oxygen Delivery (DO₂) Calculator
Oxygen Delivery (DO₂) Calculator
Calculate DO₂ from oxygen content and cardiac output, and see why chasing a supranormal target does not help.
Oxygen Delivery (DO₂)
4 inputs → deliveryHb 13 g/dL, SaO₂ 97%, PaO₂ 95 mmHg, cardiac output 5 L/min
Formula
- CaO₂
- arterial oxygen content, mL O₂/dL — see the CaO₂ calculator
- cardiac output
- L/min
- × 10
- converts CaO₂ from mL/dL to mL/L so the units match cardiac output
Worked example
Hb 13 g/dL, SaO₂ 97%, PaO₂ 95 mmHg, cardiac output 5 L/min
CaO₂ = 1.34 × 13 × 0.97 + 0.003 × 95 = 17.18 mL O₂/dL
17.18 × 5 × 10 = 859 mL O₂/min
Delivery versus consumption
| Quantity | Typical adult value |
|---|---|
| DO₂ (delivery) | 900 – 1100 mL/min |
| VO₂ (consumption) | ≈ 250 mL/min |
| Ratio | Delivery exceeds demand roughly fourfold |
| Critical DO₂ threshold | ≈ 300 – 330 mL/min — below this, VO₂ becomes delivery-dependent |
Why more delivery is not always better
Oxygen delivery is the product of arterial oxygen content and cardiac output, scaled by 10 to convert content from mL/dL to mL/L. In a healthy resting adult it runs to roughly 900–1100 mL/min, against an oxygen consumption of only about 250 mL/min — a fourfold reserve that explains why the body tolerates moderate anaemia, a modest fall in saturation, or a reduced cardiac output without any measurable shortfall in tissue oxygenation. Consumption stays flat because tissues simply extract a larger fraction of what is delivered.
That compensation has a limit. Below a critical delivery threshold, conventionally cited around 300–330 mL/min, extraction can no longer keep pace and oxygen consumption starts to fall in step with delivery — the delivery-dependent phase, and the point at which anaerobic metabolism and lactate rise begin.
The equation also explains why the three inputs are not interchangeable in practice. Raising PaO₂ with supplemental oxygen barely moves DO₂ once saturation is already high, because dissolved oxygen is such a small fraction of content; raising haemoglobin or cardiac output moves it far more. This is precisely why the once-popular strategy of driving DO₂ to supranormal targets in critically ill patients — using inotropes and transfusion to push delivery above the normal range — was tested directly and found not to improve survival, and in some trials caused harm through excess transfusion and arrhythmia. The goal now is to treat delivery deficits, not to chase an arbitrary target above normal.
Frequently asked questions
What is the formula for oxygen delivery?
DO₂ = CaO₂ × cardiac output × 10, where CaO₂ is arterial oxygen content in mL/dL, cardiac output is in L/min, and the factor of 10 converts dL to L.
What is a normal oxygen delivery?
Roughly 900–1100 mL/min in a resting adult, against a consumption of about 250 mL/min — delivery normally exceeds demand about fourfold.
What happens below the critical DO₂ threshold?
Oxygen consumption, normally independent of delivery, starts to fall alongside it — the delivery-dependent phase, occurring below roughly 300–330 mL/min, and the point at which anaerobic metabolism and lactate begin to rise.
Does raising DO₂ above normal improve outcomes?
No. Trials that deliberately drove DO₂ to supranormal targets with inotropes and transfusion did not improve survival and in some cases caused harm. The goal is to correct a deficit, not to exceed the normal range.
Related calculators
References
- Leach RM, Treacher DF. The pulmonary physician in critical care: oxygen delivery and consumption. Thorax. 2002;57(2):170–7.
- Hayes MA et al. Elevation of systemic oxygen delivery in the treatment of critically ill patients. N Engl J Med. 1994;330(24):1717–22.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.