Calculates indexed systemic oxygen consumption from cardiac index and the arterial–venous oxygen-content difference using the Fick principle.
Overview
Calculates indexed systemic oxygen consumption from cardiac index and the arterial–venous oxygen-content difference using the Fick principle.
Clinical Significance
VO₂I estimates whole-body oxygen uptake using the Fick principle. Accuracy depends on the cardiac-index method and paired blood samples.
When to Use
- Use for transparent bedside physiology when all source measurements and units are reliable.
- Use as an adjunct to clinical assessment and serial haemodynamic review.
How It Is Calculated
- VO₂I = 10 × cardiac index × (CaO₂ − CvO₂).
Interpretation
- VO₂I estimates whole-body oxygen uptake using the Fick principle. Accuracy depends on the cardiac-index method and paired blood samples.
Worked Example
Enter validated measurements in the displayed units. MedicalC applies: VO₂I = 10 × cardiac index × (CaO₂ − CvO₂).
Patient Considerations
- Applicable to physiological assessment in selected adult and paediatric settings. Sedation, fever, shivering, sepsis, exercise and extracorporeal support materially alter demand and measurement validity.
Limitations
- Calculated global oxygen variables do not show regional perfusion or microcirculatory distribution.
- Measurement errors in haemoglobin, saturation, gas tension or flow propagate into the result.
- Reference values and intervention thresholds vary by clinical context.
Clinical Pearls
- When cardiac output and blood samples are not truly contemporaneous, a precise-looking VO₂I may represent arithmetic rather than physiology.
- Trend physiology over time rather than reacting to an isolated calculated value.
Common Mistakes
- Entering saturation as a decimal when the field requests percent.
- Mixing g/L with g/dL.
- Using central venous and mixed venous measurements interchangeably.
- Combining measurements taken at materially different times.
Evidence Base
Basnet A, et al. Calculating Fick cardiac output and input. StatPearls. Updated 2024.
Frequently Asked Questions
What does this calculator estimate?
Calculates indexed systemic oxygen consumption from cardiac index and the arterial–venous oxygen-content difference using the Fick principle.
Can this result prove tissue oxygenation is adequate?
No. It describes global oxygen physiology and must be interpreted with perfusion, lactate, organ function and clinical context.
Why do measurement timing and sample source matter?
The calculation assumes that the values describe the same physiological state and the intended arterial or venous compartment.
Should I use pulse oximetry or co-oximetry?
Use the measurement method appropriate to the clinical question. Co-oximetry is preferred when dyshemoglobinaemia or saturation accuracy is a concern.
What should be reassessed after an intervention?
Check sampling simultaneity, catheter source, cardiac-index technique, temperature, sedation, work of breathing, haemoglobin, lactate and serial trends.
References
- Basnet A, et al. Calculating Fick cardiac output and input. StatPearls. Updated 2024. — Physiological, clinical or methodological source.
Reviewed by: MedicalC Clinical Editorial Team
Last reviewed: July 2026