Sources: Disturbances Of The Heart
It is essential that the patient on whom the examination is to be
made should be at rest, either comfortably seated, or lying down.
All clothing should be removed from the arm, and there should be no
constriction by sleeves, either of the upper arm or the axilla. When
the blood pressure is taken over the sleeve of a garment, the
instrument will register from 10 to 30 mm. higher than on the bare
arm. [Footnote: Rowan, J. J.: The Practical Application of Blood
Pressure Findings, The JOURNAL A. M. A., March 18, 1916, p. 873.]
While it may be better, for insurance examinations, to take the
blood pressure of the left arm in right handed persons as a truer
indicator of the general condition, the difference is generally not
great. The right arm of right handed persons usually registers a
full 5 mm. higher systolic pressure than the left arm.
The patient, being at rest and removed as far as possible from all
excitement, may be conversed with to take his mind away from the
fact that his blood pressure is being taken. He also should not
watch the dial, as any tensity on his part more or less raises the
systolic pressure, the diastolic not being much affected by such
nervous tension. The armlet having been carefully applied, it is
better to inflate gradually 10 mm. higher than the point at which
the pulsation ceases in the radial. The stethoscope is then firmly
applied, but with not too great pressure, to the forearm just below
the flexure of the elbow. The exact point at which the sound is
heard in the individual patient, and the exact amount of pressure
that must be applied, will be determined by the first reading, and
then thus applied to the second reading. One reading is never
sufficient for obtaining the correct blood pressure. The blood
pressure may be read by means of the stethoscope during the gradual
raising of pressure in the cuff, note being taken of the first sound
that is heard (the diastolic pressure), and the point at which all
sound disappears, as the pressure is increased (the systolic
pressure). The former method is the one most frequently used.
By taking the systolic and diastolic pressures, the difference
between the two being the pressure pulse, we learn to interpret the
pressure pulse reading. While the average pressure pulse has
frequently been stated as 30 mm., it is probable that 35 at least,
and often 40 mm. represents more nearly the normal pressure pulse,
and from 25 mm. on the one hand to 50 on the other may not be
Faught [Footnote: Faught: New York Med Jour., Feb. 27, 1915, p.
396.] states his belief that the relation of the pressure pulse to
the diastolic pressure and the systolic pressure are as 1, 2 and 3.
In other words, a normal young adult with a systolic pressure of 120
should have a diastolic pressure of 80, and therefore a pulse
pressure of 40. If these relationships become much abnormal, disease
is developing and imperfect circulation is in evidence, with the
danger of broken compensation occurring at some time in the future.
It should be remembered that the diastolic pressure represents the
pressure which the left ventricle must overcome before the blood
will begin to circulate, that is, before the aortic valve opens,
while the pressure pulse represents the power of the left ventricle
in excess of the diastolic pressure. Therefore it is easy to
understand that a high diastolic pressure is of serious import to
the heart; a diastolic pressure over 100 is significant of trouble,
and over 110 is a menace.