Cardiac Output Calculator
Understanding Cardiac Output (CO)
Cardiac Output (CO) is a fundamental measure of the efficiency of the cardiovascular system. It represents the volume of blood the heart pumps per minute. A healthy cardiac output is crucial for delivering oxygen and nutrients to the body's tissues and organs.
The primary formula for calculating Cardiac Output is elegantly simple:
Cardiac Output (CO) = Stroke Volume (SV) × Heart Rate (HR)
Key Components:
- Stroke Volume (SV): This is the amount of blood ejected from the left ventricle of the heart with each single heartbeat. It's typically measured in milliliters (mL). Factors influencing stroke volume include preload (the stretch of the ventricular muscle), afterload (the resistance the heart must overcome to eject blood), and myocardial contractility.
- Heart Rate (HR): This is the number of times the heart beats per minute, measured in beats per minute (bpm). Heart rate is influenced by the body's metabolic demands, autonomic nervous system activity, and various physiological and pathological conditions.
Units and Conversion:
When Stroke Volume is in milliliters (mL) and Heart Rate is in beats per minute (bpm), the resulting Cardiac Output is in milliliters per minute (mL/min). For clinical relevance, Cardiac Output is most commonly expressed in liters per minute (L/min). To convert from mL/min to L/min, divide by 1000.
Clinical Significance:
Cardiac Output is a vital indicator in various clinical settings:
- Assessing Heart Function: Low cardiac output can indicate heart failure or other cardiac conditions.
- Monitoring Critically Ill Patients: In intensive care units, CO monitoring helps guide fluid management and vasopressor therapy.
- Exercise Physiology: During exercise, CO increases significantly to meet the elevated metabolic demands of the muscles.
- Pharmacological Effects: Many cardiac medications work by altering stroke volume or heart rate, thereby affecting cardiac output.
Example Calculation:
Let's consider a healthy adult at rest with:
- Stroke Volume (SV) = 70 mL
- Heart Rate (HR) = 75 bpm
Using the formula:
CO = 70 mL × 75 bpm = 5250 mL/min
Converting to liters per minute:
CO = 5250 mL/min / 1000 = 5.25 L/min
This calculated value of 5.25 L/min falls within the typical resting cardiac output range for an adult.