Cardiac Output Calculator

Calculate cardiac output, stroke volume, and cardiac index using multiple methods

Patient Information (for Cardiac Index)

Normal: 60-100 mL/beat

Normal resting: 60-100 bpm

Understanding Cardiac Output

Cardiac output (CO) is the volume of blood pumped by the heart per minute, measured in liters per minute (L/min). It is a fundamental measure of cardiovascular function and represents the amount of blood delivered to the body's tissues to supply oxygen and nutrients while removing carbon dioxide and metabolic waste products. Cardiac output is the product of stroke volume (blood pumped per beat) and heart rate (beats per minute).

Key Parameters

Cardiac Output (CO)

CO = Stroke Volume × Heart Rate

Normal range: 4-8 L/min at rest (varies with body size and fitness level)

Stroke Volume (SV)

Volume of blood ejected by the left ventricle with each contraction

Normal range: 60-100 mL/beat (70 mL average)

Heart Rate (HR)

Number of cardiac cycles (heartbeats) per minute

Normal resting range: 60-100 bpm (lower in trained athletes)

Cardiac Index (CI)

CI = Cardiac Output / Body Surface Area

Normal range: 2.5-4.0 L/min/m² (accounts for body size differences)

Measurement Methods

Fick Principle (Gold Standard)

Based on oxygen consumption and arteriovenous oxygen difference. Most accurate but invasive.

CO = VO₂ / (CaO₂ - CvO₂) × 10
  • • VOâ‚‚ = Oxygen consumption (mL/min)
  • • CaOâ‚‚ = Arterial oxygen content (mL Oâ‚‚/dL blood)
  • • CvOâ‚‚ = Mixed venous oxygen content (mL Oâ‚‚/dL blood)
  • • Requires pulmonary artery catheterization

Thermodilution (Pulmonary Artery Catheter)

Cold saline injected into right atrium; temperature change measured at pulmonary artery.

  • • Widely used in intensive care
  • • Invasive but relatively safe
  • • Continuous monitoring possible
  • • Subject to technical errors

Echocardiography (Ultrasound)

Non-invasive imaging to measure left ventricular outflow tract diameter and velocity.

  • • Most common non-invasive method
  • • Calculates stroke volume from LVOT diameter and VTI
  • • Real-time visualization of heart function
  • • Operator-dependent accuracy

Impedance Cardiography

Measures changes in thoracic electrical impedance during cardiac cycle.

  • • Completely non-invasive
  • • Continuous monitoring
  • • Lower accuracy than invasive methods
  • • Useful for trending changes

Factors Affecting Cardiac Output

Factors Increasing CO

  • â–² Exercise: Increases both HR and SV, can reach 20-25 L/min in athletes
  • â–² Sympathetic Stimulation: Epinephrine and norepinephrine increase contractility
  • â–² Increased Preload: Greater venous return stretches ventricle (Frank-Starling)
  • â–² Reduced Afterload: Lower arterial pressure eases ejection
  • â–² Pregnancy: Increases by 30-50% to support fetal circulation
  • â–² Anxiety/Stress: Acute sympathetic activation

Factors Decreasing CO

  • â–¼ Heart Failure: Reduced contractility impairs pumping ability
  • â–¼ Myocardial Infarction: Damaged heart muscle reduces SV
  • â–¼ Hypovolemia: Low blood volume reduces preload and SV
  • â–¼ Severe Bradycardia: Very slow HR limits CO even with high SV
  • â–¼ Increased Afterload: High arterial pressure impedes ejection
  • â–¼ Valvular Disease: Stenosis or regurgitation reduces effective output

Clinical Significance

Low Cardiac Output (<4 L/min or CI <2.5)

Causes: Heart failure, cardiogenic shock, severe arrhythmias, hypovolemia, tamponade

Symptoms: Fatigue, weakness, confusion, cold extremities, low blood pressure, poor urine output

Normal Cardiac Output (4-8 L/min or CI 2.5-4.0)

Indicates: Adequate tissue perfusion and oxygenation at rest

Note: Normal values vary with age, body size, fitness level, and activity state

High Cardiac Output (>8 L/min or CI >4.0)

Physiological: Exercise, pregnancy, anxiety, fever

Pathological: Hyperthyroidism, severe anemia, septic shock, arteriovenous fistula, beriberi

References

Cardiac output measurement and interpretation are based on established cardiovascular physiology principles:

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Medical Disclaimer: This calculator is for educational and informational purposes only. Cardiac output values should be interpreted by qualified healthcare professionals in the context of complete clinical assessment. This tool does not replace professional medical evaluation, diagnosis, or treatment. Actual cardiac output measurements require appropriate medical equipment and trained personnel. If you have concerns about cardiovascular function, consult a healthcare provider.

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