This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
Why oxygen delivery matters
Cells need a constant supply of oxygen. Oxygen delivery (DO2) is the amount of oxygen the heart pumps to the tissues each minute. It depends on three things: how much hemoglobin the blood carries, how saturated that hemoglobin is, and how much blood the heart pumps.
The formulas
- Arterial oxygen content: CaO2 (mL/dL) = 1.34 × Hb (g/dL) × SaO2 + 0.003 × PaO2 (mmHg)
- Oxygen delivery: DO2 (mL/min) = cardiac output (L/min) × CaO2 × 10
- Delivery index: DO2I = DO2 ÷ body surface area
- Consumption: VO2 = cardiac output × (CaO2 − CvO2) × 10
- Extraction ratio: O2ER = (CaO2 − CvO2) ÷ CaO2
Each gram of fully saturated hemoglobin binds about 1.34 mL of oxygen; the dissolved fraction (0.003 × PaO2) is small unless the patient breathes high oxygen concentrations or is in a hyperbaric chamber.
Example
With Hb 14 g/dL, SaO2 98%, PaO2 95 mmHg and a cardiac output of 5 L/min, CaO2 = 18.7 mL/dL and DO2 = 933 mL/min. For a body surface area of 1.8 m², DO2I is 519 mL/min/m². With a venous saturation of 75%, VO2 is 224 mL/min and the extraction ratio is 24%.
| Value | Usual resting range in adults |
|---|---|
| CaO2 | 17 to 20 mL/dL |
| DO2 | 900 to 1,100 mL/min |
| DO2I | 500 to 600 mL/min/m² |
| VO2 | 200 to 250 mL/min |
| O2ER | 20 to 30% |
What the numbers show
- Anemia lowers DO2 as much as hypoxemia: halving the hemoglobin halves the oxygen content.
- When DO2 falls, tissues first extract more oxygen; venous saturation drops.
- Below a critical DO2I of about 330 mL/min/m², consumption starts to fall with delivery and lactate rises.
These are bedside physiology estimates. Measurements of cardiac output vary with the method, and clinical decisions rely on the whole picture, including lactate and organ function.