Fick Cardiac Output & Cardiac Index Calculator
Calculate Fick cardiac output from oxygen consumption and arterial–mixed-venous oxygen data, with optional cardiac index, stroke volume, SVI, and a complete calculation audit.
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About
This Fick cardiac output calculator applies oxygen mass balance to one reasonably stable hemodynamic record. It requires an explicit VO₂ source plus arterial and true mixed-venous oxygen content, and can optionally derive cardiac index, stroke volume, and stroke volume index. [1, 3]
A result is called Direct Fick only when VO₂ was directly measured. An externally assumed or estimated VO₂ can reproduce an existing record, but it remains an indirect estimate; this page never invents VO₂ from age, sex, heart rate, height, weight, or BSA. [1, 6, 7]
Formula
Interpretation
| Measure | 2022 ESC/ERS Table 11 reference | How this page uses it |
|---|---|---|
| Cardiac output | 4–8 L/min | Static context only |
| Cardiac index | 2.5–4.0 L/min/m² | Shown only with entered BSA |
| Stroke volume | 60–100 mL/beat | Shown only with entered heart rate |
| Stroke volume index | 33–47 mL/beat/m² | Shown only with both optional inputs |
These guideline table values are descriptive hemodynamic reference context, not diagnostic categories, treatment thresholds, or patient-specific targets. Interpretation also depends on body size, metabolic state, measurement method, disease context, and timing. [2]
Direct Fick, indirect Fick, and thermodilution
Direct Fick uses directly measured whole-body VO₂. Indirect Fick substitutes an assumed or estimated VO₂ and can carry clinically important error. Thermodilution is a separate cardiac-output method, not an input or output of this calculator. Current ESC/ERS guidance accepts direct Fick or repeated thermodilution and describes indirect Fick as less reliable; the 2024 heart-failure RHC guidance similarly emphasizes method provenance. [1, 2, 8]
True mixed venous sampling and shunts
This implementation requires a pulmonary-artery true mixed-venous sample. It does not convert central venous ScvO₂ into SvO₂. Suspected shunts require compartmental oximetry and a fuller invasive assessment; this page does not calculate Qp/Qs, PVR, or SVR. [2, 3]
Keep one stable hemodynamic state
Use VO₂, Hb, arterial oxygen data, pulmonary-artery mixed-venous oxygen data, and optional heart rate from the same reasonably stable state. Arterial saturation may come from a corresponding arterial blood sample or an appropriate contemporaneous systemic oximetry record; this calculator cannot verify sample quality or dyshemoglobinemia. If PaO₂ is entered, it must come from the corresponding arterial sample. Do not combine pre- and post-treatment values, unrelated time points, rest and exercise records, or different oxygen-support states. High inspired oxygen can make dissolved oxygen and measurement limitations more important. [1, 3]
Distinct adjacent calculations
If BSA is not already recorded, use the Adult Anthropometry workspace and carry the chosen formula result back explicitly. MAP and Shock Index are adjacent circulation measures but do not answer the Fick oxygen-balance question. This page does not prescribe fluids, vasopressors, inotropes, or any other treatment.
References
- Rajagopalan N, Borlaug BA, Bailey AL, et al. Practical Guidance for Hemodynamic Assessment by Right Heart Catheterization in Management of Heart Failure. JACC Heart Fail. 2024;12(7):1141–1156. PMID 38960519. DOI 10.1016/j.jchf.2024.03.020.
- Humbert M, Kovacs G, Hoeper MM, et al. 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Heart J. 2022;43(38):3618–3731. DOI 10.1093/eurheartj/ehac237.
- Wilkinson JL. Haemodynamic calculations in the catheter laboratory. Heart. 2001;85(1):113–120. PMID 11119478. PMCID PMC1729580. DOI 10.1136/heart.85.1.113.
- Rhodes CE, Denault D, Varacallo MA. Physiology, Oxygen Transport. StatPearls [Internet]. StatPearls Publishing; 2026. PMID 30855920. Bookshelf ID NBK538336.
- Sarkar M, Niranjan N, Banyal PK. Mechanisms of hypoxemia. Lung India. 2017;34(1):47–60. PMID 28144061. PMCID PMC5234199. DOI 10.4103/0970-2113.197116.
- Dehmer GJ, Firth BG, Hillis LD. Oxygen consumption in adult patients during cardiac catheterization. Clin Cardiol. 1982;5(8):436–440. PMID 7127921. DOI 10.1002/clc.4960050803.
- LaFarge CG, Miettinen OS. The estimation of oxygen consumption. Cardiovasc Res. 1970;4(1):23–30. PMID 5416840. DOI 10.1093/cvr/4.1.23.
- Narang N, Thibodeau JT, Parker WF, et al. Comparison of Accuracy of Estimation of Cardiac Output by Thermodilution Versus the Fick Method Using Measured Oxygen Uptake. Am J Cardiol. 2022;176:58–65. PMID 35613956. PMCID PMC9648100. DOI 10.1016/j.amjcard.2022.04.026.
FAQ
Cardiac output equals oxygen consumption (VO₂) divided by the arterial-minus-mixed-venous oxygen-content difference. Because this calculator uses oxygen content in mL O₂/dL, it applies CO (L/min) = VO₂ (mL/min) ÷ [(CaO₂ − CvO₂) × 10].
Sources: [3]
Cardiac output is flow in L/min. Cardiac index divides that flow by an explicitly entered body surface area and is reported in L/min/m². This page does not assume 1.73 m² or choose a BSA formula.
Sources: [2]
When heart rate is entered from the same hemodynamic state, stroke volume equals cardiac output × 1000 ÷ heart rate. When BSA is also entered, stroke volume index equals stroke volume ÷ BSA. Missing optional inputs remain unavailable rather than being defaulted.
Sources: [2]
Related Calculators
MAP
Calculate conventional mean arterial pressure from one paired systolic and diastolic blood-pressure reading, with pulse pressure and a transparent formula audit.
Anthropometry
Calculate adult body surface area (BSA) with an explicitly selected Mosteller, Du Bois, or Haycock formula and BMI from height and weight; add optional measurements for other named anthropometry models.
Shock Index
Calculate traditional adult Shock Index from paired heart rate and systolic blood pressure.
Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.