Blood-pressure primer : the sphygmomanometer and its practical application / by Francis Ashley Faught.

  • Faught, Francis Ashley, 1881-1963.
Date:
1914
    applied. The fingers should be in a comfortable posi- tion and under no circumstance should be moved during the observation. Care should also be observed that the pulse is not cut off by undue pressure of the palpating fingers. The cuff should be in the same horizontal plane as the subject's heart. ANEROID Fig. 17.—Diagram of internal mechanism, showing com- pression chambers. Note the fact that in this instrument the pressure itself is applied on the outside of the metallic chambers, so that they are compressed and not expanded, in propor- tion to the degree of compression force exerted. While the pulse is thus under observation, the pressure in the apparatus is raised by means of the hand bellows or pump until the pressure within the constricting band is sufficient to prevent the impulse from reaching the wrist. When this is accomplished the cock in the nipple M is closed to eliminate the elastic pressure. Now by a fraction of a turn in the valve N the pressure in the system is slowly released. During this part of the procedure, a close watch
    should be kept upon the height of the mercury column and for the return of the first pulse beat at the wrist. The level of the mercury column at the instant that the pulse passes the compression-band will represent the systolic pressure in the vessel under observation. It is advisable to repeat this procedure a few times to check the correctness of the finding. The diastolic pressure may be obtained in several ways. The method employed will depend upon the character of the instrument used and the method preferred by the operator. The readings obtained by this instrument correspond closely to those obtained by auscultation. The methods will be described in the order in which they have been devised. The visual method depends on the to-and-f ro motion imparted to the mercury in the "U" tube, which occurs after the pressure has fallen below the systolic point. Having determined the systolic pressure, again raise the pressure to a few millimeters above this point and immediately close the valve M. Now allow the pressure to fall very slowly by releasing the air through the valve N. As the mercury falls below the systolic point it will be noted that it acquires a rhythmic motion corre- sponding in time to the pulse. This will be found to gradually increase in amplitude up to a certain point, after which it decreases and finally ceases before zero pressure is reached. During this gradual fall the base of the mercury column, when the mercury is making the greatest excursion, represents the diastolic pressure. These are the same as are described under Pocket Apparatus on page 36.
    The Fedde Indic. By Diastolic Indicator.—This is very similar lo the visual method, except that the movement of the mercury column is ignored and the movement of the pith ball in the small vertical tube relied upon to de- termine the diastolic pressure. By reference to Fig. 18 it will be noted that the narrow perpendicular glass tube contains a small, light ball of pith or cork, which is free to move up and down within the tube. Fig. 18.—Fedde Indicator as Component of Standard Sphygmomanometer. When determining the systolic pressure pay no attention to this indicator, as each impact of air will make the ball dance violently, but this has no bearing on the test. When the pressure has reached the systolic point, close the valve N, when the ball will begin to move slightly in rhythm with the pulse. This motion gradually increases, until it reaches a maxi- mum as the level of the mercury column gradually
    falls, when, quite suddenly, its motion becomes markedly less. At the moment of this reduced move- ment the level of the mercury will indicate the diastolic pressure. Cautions.—To obtain accurate and reliable clinical data with the sphygmomanometer, it is important that some systematic technic be adhered to, and that all observations not only on the same patient, but in all cases, be made under as nearly the same conditions as possible. Attention to detail will eliminate largely the errors arising from such factors as position of the patient, presence of fatigue or mental excitement, arm used for observation, etc. It is also valuable to note the apparatus used, the time of day, the pulse rate, the sex and age of the patient. It is important that the location of the cuff should be at the heart level, otherwise the reading will be affected by the weight of gravity on a column of blood, being higher or lower, according to whether the cuff is above or below the heart level. The further the cuff is below the heart level the higher the reading. Position of Patient.—From the studies of Sandford and others, as recorded on page 55, it will be seen that the position of the patient is of great importance, as the systolic pressure under the same conditions rises from 5 to 15 mm., as the posture of the patient chances from the standing to the recumbent posture. Continued constriction of the arm by the cuff for more than a minute or two will provoke vaso-motor changes in the member, which may cause a rise of from 5 to 10 mm. in subsequent readings. Another point of importance in connection with the
    actual use of the blood-pressure apparatus is that when taking the systolic pressure the reading should never be made as the pressure is being raised in the cuff, but only after the obstruction of the vessel is com- plete by the air in the cufT and while the column is returning by means of the escape of air through the valve. Experience has shown that there is a differ- ence of several millimeters between readings made in these two ways, and that the reading taken at the moment of the return of the first impulse at the wrist is the true systolic pressure. No single reading should be accepted when it is possible to make more than one. It is better to see the patient a number of times under varying condi- tions before deciding what his blood-pressure is. The following printed record form has been taken from the Author's Work on Essentials of Laboratory Diagnosis, 4th edition, F. A. Davis Co., Philadelphia, 1912. This will be found useful for keeping a com- plete record of the Blood-pressure Test, also the chart as shown in Fig. 19 (page 51) is valuable where a series of observations are made upon one patient. This chart is arranged to keep the readings in graphic form, similar to the usual temperature chart. Some observers prefer the graphic charts which show the variation in blood-pressure and pulse in the same manner as a temperature chart. The accompanying cut shows a chart which has been carefully prepared and which is arranged to show both systolic and diastolic pressure, together with pulse rate, in such a manner that they do not become superposed. These may be obtained on the market in pads of 25 for a nominal figure or directly by writing to G. P. Pilling & Son Co., Philadelphia.