Automated Constant Cuff Pressure System to Measure Average Systolic and Diastolic Blood Pressure in Man.
HARVARD MEDICAL SCHOOL BOSTON MASS DEPT OF PSYCHIATRY
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An automated constant cuff-pressure system to remotely determine average human blood pressure levels was developed to overcome problems in measurement caused by natural beat-to-beat fluctuations in arterial pressure. A standard blood pressure cuff is inflated to approximately systolic pressure for a prescribed number of heart cycles. Korotkoff K sounds are picked up by a crystal microphone over the brachial artery. The ECG is recorded and an electronic coincidence circuit detects the number of R waves followed by a K sound. Cuff pressure is automatically adjusted until there is a 50 coincidence of R-K sounds. This cuff pressure is now by definition the median systolic pressure. The same procedure is followed to determine median diastolic pressure. A change is 2 mm Hg in cuff pressure alters the R-K coincidence by 25, insuring an accuracy of measurement of plus or minus 2 mm Hg. Average measures of pressure obtained by the constant cuff pressure method were demonstrated to be as accurate as averages based on intra-arterial readings. Application of this system in epidemiological screening is discussed. Author
- Biomedical Instrumentation and Bioengineering