File:A text-book of physiology - for medical students and physicians (1916) (14583597260).jpg

Identifier: textbookofphysio1916howe (find matches)
Title: A text-book of physiology : for medical students and physicians
Year: 1916 (1910s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology Medicine
Publisher: Philadelphia and London : W. B. Saunders Company
Contributing Library: Yale University, Cushing/Whitney Medical Library
Digitizing Sponsor: Open Knowledge Commons and Yale University, Cushing/Whitney Medical Library

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minedrapidly with approximate accuracy. In this method the cuffwith its pneumatic bag (a) is placed round the arm above the elbow,and by means of a bulb (c) or pump the pressure within the pneu-matic bag is raised until the brachial artery is completely obliter-ated. A stethoscope is now applied to the location of the brachialartery just below the lower edge of the cuff, and by means of aneedle valve the pressure on the artery is allowed to drop slowly.The moment that the pressure falls to a point at which a pulsewave can break through the constricted area a distinct soundwill be heard in the stethoscope. If the mercury manometer isread at this point, it will give the value for the systolic pressure.As the outside pressure continues to fall the sound becomes fuller, 502 CIRCULATION OF BLOOD AND LYMPH. and at a certain point disappears entirely. The pressure, as re-corded by the manometer, at which the arterial sound disap-pears marks the diastolic pressure, approximately at least. Ac-
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Fig 202.—Record (Erlanger) to show the maximum size of the recorded pulsewave when the outside or extravascular pressure is equal to the internal diastolic pressureihe artery is compressed first with.a pressure above systolic, sufficient to obliterate thelumen. As this pressure is lowered in steps of 5 mms. the recorded pulse wave increases insize to a maximum and then again becomes smaller. The outside pressure with which themaximum pulse is obtained measures the amount of the internal diastolic pressure (Mareys cording to some observers, the diastolic pressure is indicatedmore accurately by a change in the character of the sound, fromsharp to dull, which takes place just before it disappears.* If,

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