Cardiac Output (CO) is a fundamental measure of cardiovascular function. It represents the volume of blood the heart pumps per minute. It's a critical indicator of how well the heart is supplying oxygen and nutrients to the body's tissues.
The Calculation
Cardiac Output is calculated using a simple yet vital formula:
Heart Rate (HR): This is the number of times the heart beats per minute. It's typically measured in beats per minute (bpm).
Stroke Volume (SV): This is the amount of blood ejected from the left ventricle of the heart during one contraction (or beat). It's usually measured in milliliters per beat (mL/beat).
The result of this multiplication is typically expressed in liters per minute (L/min) for clinical relevance, as the stroke volume is often in milliliters. To convert milliliters per minute to liters per minute, divide by 1000.
Why is Cardiac Output Important?
Cardiac Output is a key determinant of systemic arterial pressure and tissue perfusion.:
Exercise: During physical activity, the body's demand for oxygen increases. The heart responds by increasing Cardiac Output, primarily through an elevated heart rate and, to some extent, stroke volume.
Health Conditions: Abnormal Cardiac Output can be indicative of various medical conditions.
Low Cardiac Output: May suggest heart failure, severe dehydration, shock, or certain arrhythmias where the heart isn't pumping effectively.
High Cardiac Output: Can be seen in conditions like sepsis, hyperthyroidism, or during strenuous exercise, where the body requires increased oxygen delivery.
Medical Monitoring: Healthcare professionals routinely monitor Cardiac Output in critical care settings to assess patient stability and the effectiveness of treatments.
Example Calculation
Let's consider an individual with a resting heart rate of 70 beats per minute and a stroke volume of 75 mL/beat.