. The clinical study of blood-pressure : a guide to the use of the sphygmomanometer in medical, surgical, and obstetrical practice, with a summary of the experimental and clinical facts relating to the blood-pressure in health and in disease . fora short period of time, but, under the conditions of this experi-ment, has a certain average level about which it fluctuatesrhythmically. This average height of the curve above thebase-line of atmospheric pressure may be easily calculated forany given period of time, and, when multiplied by 2,* givesan exact measure in mm. Hg. of the average or mean b
. The clinical study of blood-pressure : a guide to the use of the sphygmomanometer in medical, surgical, and obstetrical practice, with a summary of the experimental and clinical facts relating to the blood-pressure in health and in disease . fora short period of time, but, under the conditions of this experi-ment, has a certain average level about which it fluctuatesrhythmically. This average height of the curve above thebase-line of atmospheric pressure may be easily calculated forany given period of time, and, when multiplied by 2,* givesan exact measure in mm. Hg. of the average or mean blood-pressure. In all accurate u-tube manometers the displacement of the surface of themercury in the two arms is, of course, equal in amount, but opposite in direc-tion ; therefore the height of the column is twice as great as the movement inthe open arm. THE MERCURIAL MANOMETER 5 3. THE ERRORS OF THE MERCURIAL MANOMETER-COMPENSATED MANOMETER So heavy a liquid as mercury cannot possibly follow therapid cardiac variations in pressure, and it isto be emphasized that the extent of these on the manometrictrace affords no measure of their actual value. Even for theaccurate determination of mean pressure, certain conditions. FlO. 1. NOKMAL MANOMETRIC TRACE. From the carotid of a dog. are necessary, the most important of which is the calibre ofthe tube. v. Kries found that a manometer of 4 mm. diam-eter gave readings which did not vairy more than three percent, from the actual mean pressure, when the pressure wassubjected to rapid variation, as in blood-pressure advocated a constriction of the tube leading from the V. Kries, Dr. Ueber die Bestimmung des Mitteldruckes durch dasQuecksilbermanometer. Arch. f. Anatomie u. Physiologie, PhysiologischeAbtheilun|;, 1878, pp. 430 and following and p. 440, 6 DIRECT MEASUREMENT OF BLOOD-PRESSURE artery, which almost obliterates the pulse wave in the ma-nometer, and Marey ^ constricted the manometer itself at onepo
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbloodpr, bookyear1904
