Systolic blood pressure measurement by detecting the photoplethysmographic pulses and electronic Korotkoff-sounds during cuff deflation.

Objective: The commonly used noninvasive techniques for blood pressure measurement, auscultatory Korotkoff-based sphygmomanometry and oscillometry, both have limitations in their clinical use. The former is relatively accurate but is limited to use in a physician's office because its automatic variant is subject to noise artifacts. Automatic oscillometers can be used at home, but their accuracy is low. In the current study, we present two electronic techniques for systolic blood pressure (SBP) measurement that are more accurate than the available techniques, and can be automated. Approach: The cuff-based electronic techniques for SBP measurement used in this study utilize a finger photoplethysmographic (PPG) signal or electronically recorded Korotkoff sounds, and detection of the first appearance of PPG or Korotkoff-based pulses during cuff deflation. Most noise artefacts were eliminated by means of a time-reference signal-a PPG signal measured in the free hand. Main results: The two electronic techniques showed good agreement. Both techniques were found to be more accurate than the auscultatory Korotkoff-based technique, the gold-reference, in those examinations where large discrepancies were found between them, since the PPG and Korotkoff-based electronic pulses appeared before Korotkoff sounds were heard. The PPG signal in the free hand, that served as a time-reference signal, enabled both electronic techniques to eliminate artefacts-noise pulses that appeared outside the time intervals in which a blood-pressure-related pulses should appear.