RECOMMENDATIONS FOR HUMAN BLOOD PRESSURE DETERMINATIONS BY SPHYGMOMANOMETERS
A statement of the Committee of the American Heart Association to Revise Standardization of Blood Pressure Readings.
It should be clearly recognized that arterial pressures cannot be measured with precision by means of sphygmomanometers. Direct registration of pressures by calibrated intra-arterial manometers have shown (1) that even during quiet breathing and slight sinus arrhythmia, systolic and diastolic pressures vary from beat to beat by several mm. Hg, and that these differences are greatly intensified during states of arrhythmia and deep breathing; (2) that auscultatory systolic readings from the brachial artery average 3 or 4 mm. Hg too low and show average scatter of ±8 mm. Hg, and (3) that auscultatory diastolic pressures taken at the point of dulling of the sounds average about 8 mm. Hg too high. The errors of clinical measurement of blood pressure can be summarized by saying