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Source: Disturbances Of The Heart
The study of the blood pressure has become a subject of great
importance in the practice of medicine and surgery. No condition can
be properly treated, no operation should be performed, and no
prognosis is of value without a proper consideration of the
sufficiency of the circulation, and the condition of the circulation
cannot be properly estimated without an accurate estimate of the
systolic and diastolic blood pressure. However perfectly the heart
may act, it cannot properly circulate the blood without a normal
tone of the blood vessels, both arteries and veins. Abnormal
vasodilatation seriously interferes with the normal circulation, and
causes venous congestion, abnormal increase in venous blood
pressure, and the consequent danger of shock and death. Increased
arterial tone or tonicity necessitates greater cardiac effort, to
overcome the resistance, and hypertrophy of the heart must follow.
This hypertrophy always occurs if the peripheral resistance is not
suddenly too great or too rapidly acquired. In other words, if the
peripheral resistance gradually increases, the left ventricle
hypertrophies, and remains for a long time sufficient. If, from
disease or disturbance in the lungs, the resistance in the pulmonary
circulation is increased, the right ventricle hypertrophies to
overcome it, and the circulation is sufficient as long as this
ventricle is able to do the work. If either this pulmonary increased
pressure or the systemic increased pressure persists or becomes too
great, it is only a question of how many months, in the case of the
right ventricle, and how many years, in the case of the left
ventricle, the heart can stand the strain.
If the cause of the increased systemic tension is an arterial
fibrosis, sooner or later the heart will become involved in this
general condition, and a chronic myocarditis is likely to result.
If, on the other hand, there is a continuous low systemic arterial
blood pressure, the circulation is always more or less insufficient,
nutrition is always imperfect, and the physical ability of the
individual is below par. It is evident, therefore, that an
abnormally high blood pressure is of serious import, its cause must
be studied, and effort must be made to remove as far as possible the
cause. On the other hand, a persistently low blood pressure may be
of serious import, and always diminishes physical ability. If
possible, the cause should be determined, and the condition
No physician can now properly practice medicine without having a
reliable apparatus for determining the blood pressure both in his
office and at the bedside. It is not necessary to discuss here the
various kinds of apparatus or what is essential in an apparatus for
it to give a perfect reading. It may be stated that in determining
the systolic and diastolic pressure in the peripheral arteries, the
ordinary stethoscope is as efficient as any more elaborate
It is now generally agreed by all scientific clinicians that it is
as essential--almost more essential--to determine the diastolic
pressure as the systolic pressure; therefore the auscultatory method
is the simplest, as well as one of the most accurate in determining
these pressures. Of course it should be recognized that the systolic
pressure thus obtained will generally be some millimeters above that
obtained with the finger, perhaps the average being equivalent to
about 5 mm. of mercury. The diastolic pressure will often range from
10 to 15 mm. below the reading obtained by other methods. Therefore,
wider range of pressure is obtained by the auscultatory method than
by other methods. This difference of 5 or more millimeters of
systolic pressure between the auscultatory and the palpatory
readings should be remembered when one is consulting books or
articles printed more than two years ago, as many of these pressures
were determined by the palpatory method.
Sometimes the compression of the arm by the armlet leads to a rise
in blood pressure. [Footnote: MacWilliams and Melvin: Brit. Med.
Jour., Nov. 7, 1914.] It has been suggested that the diastolic
pressure be taken at the point where the sound is first heard on
gradually raising the pressure in the armlet.
In some persons the auscultatory readings cannot be made, or are
very unsatisfactory, and it becomes necessary to use the palpation
method in taking the systolic pressure. In instances in which the
auscultatory method is unsatisfactory, the artery below the bend of
the elbow at which the reading is generally taken may be misplaced,
or there may be an unusual amount of fat and muscle between the
artery and the skin.
The various sounds heard with the stethoscope, when the pressure is
gradually lowered, have been divided into phases. The first phase
begins with the first audible sound, which is the proper point at
which to read the, systolic pressure. The first phase is generally,
not always, succeeded by a second phase in which there is a
murmurish sound. The third phase is that at which the maximum sharp,
ringing note begins, and throughout this phase the sound is sharp
and intense, gradually increasing, and then gradually diminishing to
the fourth phase, where the sound suddenly becomes a duller tone.
The fourth phase lasts until what is termed the fifth phase, or that
at which all sound has disappeared. As previously stated, the
diastolic pressure may be read at the beginning of the fourth phase,
or at the end of the fourth phase, that is, the beginning of the
fifth; but the difference is from 3 to 10 mm. of mercury, with an
average of perhaps 5 mm.; therefore the difference is not very
great. When the diastolic pressure is high, for relative subsequent
readings, it is much better to read the diastolic at the beginning
of the fifth phase.
It is urged by many observers that the proper reading of the
diastolic pressure is always at the beginning of the fourth phase.
However, for general use, unless one is particularly expert, it is
better to read the diastolic pressure at the beginning of the fifth
phase. There can rarely be a doubt in the mind of the person who is
auscultating as to the point at which all sound ceases. There is
frequently a good deal of doubt, even after large experience, as to
just the moment at which the fourth phase begins. With the
understanding that the difference is only a few millimeters, which
is of very little importance, when the diastolic pressure is below
95, it seems advisable to urge the reading of the diastolic pressure
at the beginning of the fifth phase.
The incident of the first phase, or when sound begins, is caused by
the sudden distention of the blood vessel below the point of
compression by the armlet. In other words, the armlet pressure has
at this point been overcome. Young [Footnote: Young: Indiana State
Med. Assn. Jour., March, 1914.] believes that the murmurs of the
second phase, which in all normal conditions are heard during the 20
mm. drop below the point at which the systolic pressure had been
read, is "due to whirlpool eddies produced at the point of
constriction of the blood vessel by the cuff of the instrument." The
third phase is when these murmurs cease and the sound resembles the
first, lasting he thinks for only 5 mm. The third phase often lasts
much longer. He thinks the fourth phase, when the sound becomes
dull, lasts for about 6 mm.
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