O2 Consumption

Oxygen Consumption (VÖ₂) Calculator

Fick Principle  ·  VÖ₂ = CO × Hb × 1.36 × (SaÖ₂ − SvÖ₂)  ·  ESC/AHA Haemodynamics 2024

Cardiac Output

Fick Principle: VÖ2 = CO × Hb × 1.36 × (SaÖ2 − SvÖ2)  ·  Normal rest: 200–300 mL/min

O₂ delivery (DÖ₂): CO × Hb × 1.36 × SaÖ2 × 10  ·  Normal: 900–1200 mL/min  ·  O₂ ER = VÖ₂ / DÖ₂

1.36 mL O₂/g Hb = Hufner constant (O₂-carrying capacity of haemoglobin)  ·  Factor ×10 converts dL→L units

Clinical scenario presets

Enter haemodynamic parameters

Haemoglobin (Hb)

g/dL

From CBC / FBC  ·  Normal: Male 13–17 g/dL, Female 12–16 g/dL  ·  1.36 mL O₂ per gram Hb (Hüfner constant)

SaÖ₂ — Arterial O₂ saturation

%

From ABG (SaO₂) or pulse oximetry  ·  Normal breathing air: 95–100%  ·  Enter as percentage (e.g. 98)

SvÖ₂ — Mixed venous O₂ saturation

%

From PA catheter (true SvO₂) or central line (ScvO₂ ≈ SvO₂+5%)  ·  Normal: 70–75%  ·  Critical: <50%

Cardiac Output (CO)

L/min

Thermodilution (PAC), PiCCO, Echocardiography (VTI × LVOT area × HR)  ·  Normal: 4–8 L/min  ·  CI = CO / BSA (normal 2.2–4.0)

BSA (optional — for indexed values)

m²

Dubois formula or Mosteller  ·  Leave blank to skip indexed values  ·  Normal: 1.6–1.9 m²

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Oxygen Consumption (VÖ₂) — Fick Principle

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VÖ₂ spectrum — current position

Low (<150)Normal (200–300)Elevated (>400)

DO₂

—

mL/min

O₂ ER

—

extraction ratio

VÖ₂I

—

mL/min/m²

CaO₂−CvO₂

—

mL O₂/dL

Oxygen delivery vs consumption

DO₂

1000 mL/min

VO₂

250 mL/min

Reserve

750 mL/min

VO₂ interpretation — clinical reference (ESC/AHA 2024)

VO2 (mL/min)	Category	Common context	O2 ER	Key action
< 150	Low	Sedation, hypothermia, critically low cardiac output	Variable	Optimise cardiac output; check metabolic rate; assess SvO2
150 – 300	Normal (rest)	Healthy resting adult; well-compensated physiology	20–30%	Reassess if SvO2 declining despite normal VO2
300 – 500	Elevated	Fever, sepsis, agitation, post-surgical stress, pain	25–35%	Treat fever/pain; consider sedation; optimise ventilation; ensure DO2 matches demand
> 500	Very high	Severe sepsis, malignant hyperthermia, seizures, heavy exercise, thyroid storm	>35%	Urgent cause identification; oxygen reserve assessment; ensure adequate DO2; specialist review

VÖ₂ = CO × Hb × 1.36 × (SaÖ₂ − SvÖ₂) / 100  ·  Fick Principle 1870  ·  Hüfner constant 1.36 mL O₂/g Hb  ·  ESC/AHA haemodynamics 2024  ·  No patient data stored

Clinical references

• 1.Fick A. Über die Messung des Blutquantums in den Herzventrikeln. Sitzungsberichte der Physikalisch-medizinischen Gesellschaft zu Würzburg. 1870:36–38. (Original Fick principle for cardiac output measurement)
• 2.Hüfner CG. Über das Gesetz der Dissociation des Oxihämoglobins. Arch Anat Physiol. 1890:1–27. (Hüfner constant — 1.36 mL O₂ per gram haemoglobin)
• 3.Rivers E, Nguyen B, Havstad S, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med. 2001;345(19):1368–1377. doi:10.1056/NEJMoa010307 (ScvO₂ ≥ 70% as resuscitation target — EGDT)
• 4.Nichols WW, O'Rourke MF, Vlachopoulos C. McDonald's Blood Flow in Arteries. 6th ed. Oxford University Press; 2011. (Comprehensive haemodynamics reference including Fick method)
• 5.Vincent JL, De Backer D. Oxygen transport — the oxygen delivery controversy. Intensive Care Med. 2004;30(11):1990–1996. doi:10.1007/s00134-004-2419-4 (Supply-dependency of oxygen consumption)
• 6.McLellan SA, Walsh TS. Oxygen delivery and haemoglobin. Contin Educ Anaesth Crit Care Pain. 2004;4(4):123–126. doi:10.1093/bjaceaccp/mkh033 (DO₂, VO₂, and O₂ extraction ratio)
• 7.Nishimura RA, Otto CM, Bonow RO, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease. J Am Coll Cardiol. 2014;63(22):e57–185. (Fick method for cardiac output in valvular disease assessment)
• 8.Weil MH, Henning RJ. New concepts in the diagnosis and fluid treatment of circulatory shock. Anesth Analg. 1979;58(2):124–132. (SvO₂ interpretation in shock states)
• 9.Squara P. Matching total body oxygen consumption and delivery: a crucial objective? Intensive Care Med. 2004;30(12):2170–2179. doi:10.1007/s00134-004-2458-x (VO₂/DO₂ relationship and supply dependency)

Frequently asked questions

Medical disclaimer

For qualified clinical professionals only. This VÖ₂ Calculator is an educational decision-support tool using the Fick principle. It is not a substitute for direct calorimetry, clinical haemodynamic assessment, or invasive monitoring interpretation by a qualified intensivist or cardiologist.

The Fick principle (VÖ₂ = CO × [CaO₂ − CvO₂]) assumes a steady state between oxygen delivery and consumption. This assumption is violated during rapid haemodynamic changes, immediately post-cardiac arrest, during active resuscitation, and when CO is measured by methods with high variability (e.g. thermodilution in tricuspid regurgitation). The Hüfner constant of 1.36 mL O₂/g Hb assumes 100% O₂ binding; the theoretical maximum is 1.39, and the clinical constant of 1.34 is also used — this tool uses 1.36 (widely accepted standard).

SvO₂ from a central venous catheter (ScvO₂) approximates but does not equal true mixed venous SvO₂ from a pulmonary artery catheter. ScvO₂ is typically 5–7% higher than SvO₂ in healthy individuals but may be lower in septic shock. Adjust interpretation accordingly. Pa cardiography and point-of-care ultrasound (POCUS) provide complementary haemodynamic assessment.

Oxygen consumption and delivery values should always be interpreted alongside the full clinical picture: mental status, lactate trend, capillary refill, urine output, and organ function markers. This tool does not store or transmit patient data.

Last reviewed: January 2026  ·  Fick 1870  ·  Hüfner constant 1.36  ·  EGDT Rivers 2001  ·  ESC/AHA haemodynamic guidelines 2024