Fig. 58.—Another method of finger-tip palpation of the radial artery. (Graves.)
Estimation of Blood Pressure
It must be borne in mind at the outset that arteriosclerosis and high blood pressure are not always associated. As a matter of fact in the severest grades of senile arteriosclerosis the blood pressure is usually below the normal for the individual's years. However, as high tension is a frequent factor in the production of arterial thickening, blood pressure readings are of importance.
The instrument which one uses is of minor importance provided it is properly standardized. The most important feature of the instrument is the cuff. This must be 12 cm. wide and be long enough to wrap around the arm several times so that the pressure is evenly distributed over the whole arm and not over a small portion. One mercury instrument we had in the hospital was reported to be at great variance with a dial instrument. This mercury instrument was provided with a cuff which was short and was tied around the arm by means of a piece of tape. This caused a tight constriction over a small area and rendered the estimation too high. A new, long tailed cuff easily remedied the apparent defect in the instrument.
In taking blood pressures the difference from day to day of 10 or even 15 mm. of systolic pressure has no great significance. Fluctuations of the systolic pressure alone, it is insisted upon, have very little meaning. One must take the whole pressure picture into consideration and determine how the picture changes in order to draw any conclusion in regard to the state of the blood pressure. Failure to pay attention to this evident point has caused much futile work to be written and published.
It is well to emphasize again the point that the blood pressure picture consists of the systolic, the diastolic, the pulse pressure and the pulse rate.
Palpation
Hoover has called attention to the direct palpation of the femoral artery just below Poupart's ligament as a more accurate index of the pressure in the aorta than the palpation of the radial artery. Possibly one can obtain a more accurate estimate of the blood pressure in this way. This, however, is open to dispute. To estimate the blood pressure by palpating the radial artery is most deceptive. In about 75 per cent of cases one can tell fairly well whether the pressure is abnormally high or abnormally low. Small variations are impossible to determine. Unquestionably it is most advantageous to get into the habit of palpating the femoral artery and checking the result with the sphygmomanometer so that the fingers may be trained to appreciate as accurately as possible changes of pressure.
It may be that one day when the instrument is needed it is not at hand. A well-trained touch then becomes a great asset.