# Cardiac Output by Fick Principle (CO) Compute CO = VO₂ / (CaO₂ − CvO₂) / 10 (L/min) with the Fick principle. Requires PA-catheter mixed venous samples. VO₂ defaults to 250 mL/min. Derived from Fick 1870, StatPearls, LITFL, West, Leach 2002. Not medical advice. > Canonical page: https://elysiatools.com/en/tools/cardiac-output-fick - **Category:** Health - **Keywords:** cardiac output, fick principle, fick cardiac output, co, oxygen consumption, vo2, arterial venous oxygen difference, cao2, cvo2, pulmonary artery catheter, hemodynamics, cardiology, critical care ## Overview The Cardiac Output by Fick Principle calculator estimates cardiac output in L/min from hemoglobin, arterial and mixed venous oxygen measurements, and oxygen consumption. It uses the Fick equation and requires mixed venous samples obtained through a pulmonary artery catheter. This tool is not medical advice. ## Inputs - **Hemoglobin (g/dL)** (number): Hemoglobin concentration (g/dL). - **SaO₂ (arterial O₂ sat, fraction)** (number): Arterial oxygen saturation as a fraction (0–1, e.g. 0.97 = 97%). - **PaO₂ (mmHg)** (number): Arterial PO₂ (mmHg) from ABG. - **SvO₂ (mixed venous O₂ sat, fraction)** (number): Mixed venous O₂ saturation (0–1) from a pulmonary artery catheter. Do NOT use a peripheral venous sample. - **PvO₂ (mixed venous PO₂, mmHg)** (number): Mixed venous PO₂ (mmHg) from a pulmonary artery catheter. - **VO₂ (O₂ consumption, mL/min, optional)** (number): Whole-body O₂ consumption (mL/min). Default 250 mL/min (~70 kg adult at rest). A directly measured value from a metabolic cart is more accurate than the estimate. - **Decimal Places** (number) ## When to use - Estimate cardiac output when arterial and pulmonary-artery mixed venous oxygen data are available. - Review the arterial–venous oxygen difference alongside the calculated Fick cardiac output. - Use a measured VO₂ value when available, or use the default estimate of 250 mL/min for a resting adult. ## How it works - Enter hemoglobin, SaO₂, PaO₂, SvO₂, and PvO₂ values using the specified units and fractional saturation format. - The calculator derives arterial oxygen content with CaO₂ = 1.34 × Hb × SaO₂ + 0.003 × PaO₂. - It derives mixed venous oxygen content with CvO₂ = 1.34 × Hb × SvO₂ + 0.003 × PvO₂. - It calculates cardiac output as CO = VO₂ ÷ (CaO₂ − CvO₂) ÷ 10 and rounds the result to the selected decimal places. ## Use cases - A critical care clinician can estimate cardiac output from pulmonary artery catheter data and arterial blood gas measurements. - A cardiology trainee can check each component of the Fick calculation, including CaO₂, CvO₂, and the oxygen difference. - A hemodynamics review can compare a resting estimate with a calculation using directly measured oxygen consumption. ## Frequently asked questions ### What inputs are required? Hemoglobin, SaO₂, PaO₂, SvO₂, and PvO₂ are required. VO₂ is optional. ### What does the default VO₂ value mean? VO₂ defaults to 250 mL/min, an estimate for a 70 kg adult at rest. ### Can I enter a measured VO₂? Yes. Enter the measured whole-body oxygen consumption in mL/min to replace the default estimate. ### What type of venous sample is needed? SvO₂ and PvO₂ should come from mixed venous blood obtained through a pulmonary artery catheter, not a peripheral venous sample. ### What does the result include? The JSON result includes cardiac output, arterial and venous oxygen content, the arterial–venous oxygen difference, and the VO₂ source. ## Related tools - [A-a Gradient (Alveolar-Arterial O₂)](https://elysiatools.com/en/tools/a-a-gradient-calculator): Calculate the alveolar-arterial O₂ gradient to distinguish hypoxemia causes. PAO₂ = FiO₂×(P_atm−47) − PaCO₂/0.8; A-a = PAO₂ − PaO₂. Normal ≈ (Age+10)/4. Elevated → V/Q mismatch, shunt, diffusion impairment. Derived from StatPearls, LITFL, Cornell PICU, and Martin 1999. Not medical advice. - [Alveolar Gas Equation (PAO₂ Calculator)](https://elysiatools.com/en/tools/alveolar-gas-equation): Calculate PAO₂ = FiO₂ × (P_atm − 47) − PaCO₂ / RQ. Defaults: P_atm 760 mmHg (sea level), RQ 0.8. Gives a directional hint vs expected ~100 mmHg. For full A-a gradient interpretation use a-a-gradient-calculator. Derived from StatPearls, LITFL, Cornell PICU, and West. Not medical advice. - [Alveolar Ventilation Calculator (VA)](https://elysiatools.com/en/tools/alveolar-ventilation-calculator): Calculate VA = (VT − VD) × RR in L/min. VD may be supplied or estimated as ~2 mL/kg body weight. Normal resting ~4–6 L/min; low → hypercapnia, high → hypocapnia. Derived from West, LITFL, StatPearls, and Radford 1955. Not medical advice. - [Apgar Score (Newborn 1 & 5 min)](https://elysiatools.com/en/tools/apgar-score): Calculate the Apgar score to assess newborn condition at 1 minute and 5 minutes after birth. Five signs are each scored 0–2 at both time points: Appearance (skin color), Pulse (heart rate), Grimace (reflex irritability), Activity (muscle tone), and Respiration. Each time point totals 0–10. Interpretation: 7–10 reassuring; 4–6 moderately abnormal (may need assistance); 0–3 critically low (immediate resuscitation). The tool reports both the 1-min and 5-min scores, the change (delta), and per-time-point interpretation. A 5-min score, and especially the change from 1 to 5 min, indicates response to resuscitation; persistent low 5-min scores warrant continued resuscitation and reassessment at 10 min. Derived from Apgar 1953, reaffirmed by ACOG/AAP. The Apgar is a physiologic snapshot at a moment in time and is not, by itself, a marker of asphyxia or long-term neurologic outcome. Not medical advice. - [OD600 to CFU/mL Converter (Calibration Curve Slope)](https://elysiatools.com/en/tools/bacterial-growth-od): Convert OD600 to CFU/mL via a calibration slope with organism presets, blank correction, dilution handling, and linearity warnings. - [Henderson-Hasselbalch Equation (pH / HCO₃⁻ / PCO₂)](https://elysiatools.com/en/tools/bicarbonate-ph-conversion): Solve any one of pH/HCO₃⁻/PaCO₂ from the other two via pH = 6.1 + log10(HCO₃⁻/(0.03×PaCO₂)). Reports linear Henderson \[H⁺\] cross-check. Derived from Henderson 1908, Hasselbalch 1916, Siggaard-Andersen 1974, LITFL, StatPearls, Berend 2016. Not medical advice. - [Bilirubin Unit Converter (mg/dL ↔ µmol/L)](https://elysiatools.com/en/tools/bilirubin-unit-converter): Convert serum bilirubin (total/direct/indirect) between mg/dL and µmol/L. Factor 17.1 (molar mass 584.67 g/mol). Derived from Young 1987, StatPearls, AAP 2004, Bhutani. Not medical advice. - [Calcium Unit Converter (mg/dL ↔ mmol/L)](https://elysiatools.com/en/tools/calcium-unit-converter): Convert total serum calcium between mg/dL and mmol/L. Factor 0.25 (atomic weight 40.078; × 4.0 inverse). Does not albumin-correct. Derived from Payne 1973, Young 1987, StatPearls, Endocrine Society. Not medical advice. ## Samples - [Web Image Processing Python Samples](https://elysiatools.com/en/samples/web-image-processing-python): Web Python image processing examples using PIL/Pillow including reading, saving, resizing, and format conversion - [Android Image Processing Java Samples](https://elysiatools.com/en/samples/android-image-processing-java): Android Java image processing examples including reading/saving images, scaling, and format conversion - [Android Image Processing Kotlin Samples](https://elysiatools.com/en/samples/android-image-processing-kotlin): Android Kotlin image processing examples including reading/saving images, scaling, and format conversion - [Web Image Processing Rust Samples](https://elysiatools.com/en/samples/web-image-processing-rust): Web Rust image processing examples including image read/save, scaling, and format conversion ## Related content - [Critical Care Blood Gas, Oxygenation, and Hemodynamics Calculators](https://elysiatools.com/en/hubs/critical-care-blood-gas-oxygenation-hemodynamics): Connect arterial blood gas, acid-base, oxygenation, cardiac output, and vascular resistance calculations in one focused critical-care workflow. - [Health Tools](https://elysiatools.com/en/hubs/health-utility): Explore 29 health tools for utility workflows and compare closely related utilities quickly. - [Meditation, Sleep, and Relaxation Tools](https://elysiatools.com/en/hubs/meditation-sleep-relaxation): Compare guided meditation, breathing routines, PMR, sleep-cycle planning, stress self-checks, and supporting audio tools in one hub for calmer daily routines. - [Endurance Training Pace, Heart Rate, and Effort Tools](https://elysiatools.com/en/hubs/endurance-training-metrics): Compare pace calculators, heart-rate zone tools, VO2 max estimates, cycling power, calorie burn, and training-load metrics in one hub for running, cycling, swimming, and triathlon planning.