What is it? Why is it Vital?
The amount of blood pumped out of the ventricle in a minute (most often refers to the blood pumped by the left ventricleThe left ventricle ejects blood into the aortic arch to the body. Within the arch, the coronary arteries branch off first followed by three main arteries that branch to the brain (carotids) and the upper thorax (subclavian artery). The chambers...)
What is cardiac output?
Simply, cardiac output is the amount of blood ejected by the left ventricle in one minute. The left ventricle seems to get the lion’s share of attention perhaps because the body’s blood flowThe purpose of the cardiac cycle is to effectively pump blood. The purpose of the cardiac cycle is to effectively pump blood. The right heart delivers deoxygenated blood to the lungs. Here oxygen is picked up and carbon dioxide is... and pulse are provided by the left ventricle.
For an adult, an average cardiac output is about 5-8 liters of ejected blood per minute. With strenuous activity, an adult’s cardiac output can increase to an amazing 25 liters per minute to satisfy the body’s demands for oxygen and nutrients.
Some of us readily remember that cardiac output is calculated via the following formula:
Cardiac Output = Stroke VolumeThe amount of blood ejected by either the right or left ventricle with one beat (contraction). While heart rate is an undisputed contributor to cardiac output, stroke volume is the other major player. As heart rates vary to changes in... x Heart RateThe number of QRS complexes per minute; note that HR may not equal perfused pulse rate. See also: - Step 1 Heart Rate - Rate - Rule of 300s (Triplicate Method) - Six Second Count - The Caliper Method 1....
or
CO = SV x HR
Cardiac output is a product of heart rateHeart Rate; calculated by counting the number of QRS complexes in six seconds and multiplying by 10; rate is also determined by measuring the number of large squares between two R waves; i.e. –1 large square = heart rate of 300/minute. (beats per minute) and stroke volume. Stroke volume is the amount of blood ejected by the left ventricle with each contraction.
Let’s put this in perspective. What is your pulse rateHeart rate is not always the same as pulse. Heart rate is a measurement of electrical activity while pulse ensures the perfusion of the blood to the target tissues. Many have been caught depending on the cardiac monitor for vital...? If a typical cardiac output is about 5000 ml (5 liters), what is your approximate stroke volume? For example, a patient named Mary has a pulse of 72/minute.
5000 = ____(SV) X 72 (HR)
With a little math, Mary’s stroke volume is calculated to be about 70 ml.
SV = 5000 / 72 = 70 ml
Therefore, each time Mary’s left ventricle beats, it ejects about 70 ml of blood. Mary turns out to be about average when it comes to stroke volume. A typical stroke volume for adults is 50-80 ml. How about your own stroke volume?
Note that the heart extracts most of the available oxygen from the blood even during periods when the body is at rest. The heart, then, has very little physiological reserve to respond to episodes of high energy demand. Rather, the heart depends almost entirely on increased coronary blood flow to satisfy high energy demand.
1. Six Second ECG GuidebookA Practice Guide to Basic and 12 Lead ECG Interpretation, written by Tracy Barill, 2012 Introduction The ability to correctly interpret an electrocardiogram (ECG), be it a simple six second strip or a 12 lead ECG, is a vital skill... (2012), T Barill, p. 24, 107, 108, 121, 193