The term of Cardiac Output (CO) has been discussed as that part of cardiac physiology that shows the heart pumping blood in term of volume either through the right or left ventricles measured by their unit times. There are different ways in which CO could be measured like the L/min and dm3/min.
The amount of blood output by the left ventricle of the heart in one contraction is called the stroke volume. The stroke volume and the heart rate determine the cardiac output.
Cardiac Output is an excellent example of how the human heart does an efficient work for maintaining the human body. It is related to the amount of blood pumped by the heart per minute. A normal CO would pump about five to six liters of blood per minute when a person is resting.
The cardiac output comprises of 2 vital components viz. SV – Stroke Volume and HR – Heart Rate.
- Heart rate refers to the number of times the heart beats every minute (bpm).
- Stroke volume refers to the quantity of blood pumped out of the left ventricle with every heartbeat.
Cardiac Output Formula
The equation for cardiac output is: Cardiac Output (CO) = HR x SV
Cardiac Output Calculation
For example: If heart rate is 70 bpm and stroke volume is 70 ml.
Using the formula: HR X SV
= 70 X 70
= 4900 ml/min or 4.9 liters per minute.
Cardiac Output Measurement
There are different merits and demerits of measuring CO using methods in an invasive and non-invasive manner. At present, there is no standard comparison system available for comparing these methods using a reference measurement or standards.
Invasive methods are well accepted, but there is increasing evidence that these methods are neither accurate nor effective in guiding therapy activities like:
- Doppler ultrasound