Blood Under Pressure
( Originally Published 1921 )
Another conception of the circulation that it is quite necessary to grasp is that the blood is under pressure, and that this pressure depends upon the contraction or firmness of the blood vessels in which it is contained. This firmness, or continuous partial contraction of the blood vessels, that keeps up the pressure of the blood is part of life itself ; when life no longer exists, the blood vessels relax and are only about half filled by the blood. Under these circumstances, the blood settles in the looser and softer blood vessels, such as the veins, and the harder and stiffer blood vessels, or arteries, are empty. This is the way they were found when the bodies of dead animals were examined by the ancient Greeks. Hence they were called arteria ("air conveyor," "wind-pipe") because they were supposed to be air tubes.
As soon as life loosens its grip on the arteries and allows them to become dilated, the circulation of course can no longer be carried on, be-cause the heart can not pump the blood unless the arteries and blood vessels are fairly well filled.
This property of muscles of being in a condition of partial contraction whenever they are alive and healthy is universal to muscles ; so that if a limb becomes paralyzed, almost immediately the muscles become loose and flabby.
Nearly all the muscles of the body are balanced against each other, so that one group of muscles pulls against the other and keeps everything steady and in shape. If a muscle becomes paralyzed, its opposing muscle draws the limb out of shape. So when a child has infantile paralysis and some of the muscles are paralyzed, great care is necessary to prevent ever increasing deformity.
This tonicity of the muscles is an important factor in health, and is a good reason for regular exercise, because a healthy tone of the muscle is reflected in a healthy tone of other organs of the body.
The heart is a muscle, and its size depends upon the tone of the muscle of which it is made up. The tone of the muscle of the heart and of the muscles which surround all the blood vessels is closely associated with the tone of the muscles that we use to move our limbs and bodies. For this reason, a great resource in regulating and controlling the condition of the heart and blood vessels in health and disease is found in exercise and those things which affect the voluntary muscles.
So we have an arrangement in the body whereby the blood is squeezed first in one place and then in another, as may be required, and at the same time it is pushed around through the Iungs to be purified by mixture with air and then again through the body to supply fresh blood to all its parts. This is brought about by two principal pumps, which, being bound together, are called the heart, and by the whole set of muscles surrounding the blood vessels.
This description ought to make it clear what is meant by blood pressure. Blood pressure is ,really pressure on the blood by the contraction of the walls of the hollow places in which it is contained just as if you held something lightly in your hand, and then closed your hand firmly upon it, or just as when you squeeze the bulb of a syringe you increase the pressure inside of it. In the same way, low blood pressure exists when there is a corresponding relaxation.
There are some ideas in connection with the circulation of the blood that are very important and should be thoroughly understood when considering heart trouble. In the first place, by circulation of the blood, I mean movement of the blood, not of necessity any particular reference to the amount of blood in any one place at any given time.
There may be a great deal of blood in a limb and yet the circulation be so poor that damage results. This is seen in people with varicose veins, where there is great congestion of the limbs, and an ulcer develops. In another case, the arteries of the limbs may be so contracted by disease that enough blood does not get to the foot to keep it nourished, and one of the toes may be lost. In the one case, there is too much blood in the limb, and in the other, there is not enough; but neither of these conditions is the cause of damage. The damage results from the lack of circulation, tho a small amount of circulation is sufficient to maintain the health of a limb.
For these reasons, a physician or nurse can not judge the efficacy of the circulation by appearances. A person may be pale and have a good circulation, or flushed and have a good circulation; or he may be either pale or flushed on account of a poor circulation. The efficacy of the circulation must be judged by its results rather than by any direct observation of the flow of the blood.
If a person is short of breath in heart disease, the circulation in the lungs is defective. In the same way, if a person suffers from cold hands and feet or from a loss of vitality in the organs, it is fair to suppose, other things being equal, that the circulation is poor.
Poor circulation, when it is a general condition, can often be remedied by the patient himself by exercise, improvement of the nervous system, rest and recreation. If it is due to any organic disease of the circulation, however, medical treatment is necessary.
The nurse can do much for the circulation by urging the necessity of exercise and by attending to proper clothing and systematic massage. All nurses who have the care of people with bad circulation should know about rubbing the extremities in such a way as to give the patient comfort.