If the auscultation method is used, the rub ber bag is inflated as in the palpation method until the pulse at the wrist is obliterated, after which the bell of an ordinary binaural stetho scope or the disc of a phonendoscope is placed over the artery at the elbow. The air pres sure is then gradually released and when the cardiac beat first passes the constricting cuff it is announced by a loud sound which is the systolic pressure. As the pressure in the in flated bag is released this sound is followed by a murmur and then by a second sound which gradually disappears. At this instant the col umn of mercury shows the diastolic pressure.
The theory is that the blood pressure in the aorta which is at the maximum when it receives its charge of blood from the left ven tricle is sustained as the blood goes through the arterial system, then as it is forced through the capillaries the pressure is reduced to its minimum and becomes the diastolic pressure. The blood pressure depends upon the contrac tile force of the heart and the peripheral re sistance to be overcome, the latter depending upon the contractility and distensibility of the walls of the blood vessels. A weak heart nec essarily will not have as high tension as a strong one, the time between the systoles will be shorter and the pulse pressure will be lower. A strong heart will have a longer interval between the systoles and a higher blood pres sure. The pulse pressure is the most impor tant factor with reference to treatment of the heart and in differentiating a cardiac from a vascular origin of a given condition.
Many important facts relating to blood pres sure are now available; some of them are the following: The standards of blood pressure vary in different individuals, in health as well as disease; in women the standard is 10 mil limetres lower than in men. The lowest re corded systolic pressure is 40; the lowest in which the patients have recovered are from 60 to 75. The systolic pressure, pulse pressure and pulse rate are increased after eating. The systolic pressure is lowered during sleep; the pulse pressure is increased by exercise and low ered by fatigue. Emotions and mental effort
cause rise in diastolic pressure. It is better to take the pressure between meals. In con ditions of disease the pressure may be high or low, continued high pressure meaning cardiac hypertrophy, changes in the arterial wall and danger of rupture. In arteriosclerosis the pressure is high, often the systolic is from 150 to 250 and the diastolic 110 to 130. In nephri tis there is often a systolic pressure of 200 and a low diastolic, with danger of apoplexy. Dur ing an attack of uremia the blood pressure is high and falls when the conditions improve. In cases of high intra-cerebral pressure the blood pressure may be as much as 300 to 400. At the end of pregnancy the pressure is some what higher than normal and should eclampsia or other toxaemia occur it would mount to a great height.
"Diseases which have low blood tension are pulmonary phthisis, cancer, syphilis, diarrhea, peritonitis, etc. From the foregoing it will be apparent that much valuable information can be obtained by the general practitioner, or, in deed, by any physician, from records of blood pressure, particularly with reference to diag nosis and prognosis. Janeway, who has prob ably investigated the subject with as much care as anybody in this country, is quoted as saying that blood pressure should always be taken at the first examination of all patients and at occasional intervals in cases of car diavascular disease and nephritis. It should be a routine practice in examinations for life in-, surance and athletic contests and it is desirable in obstetric, medical and surgical conditions in general. Consult
W.,