The origin of Korotkoff sounds and the accuracy of auscultatory blood pressure measurements

Abstract

This study explores the hypothesis that the sharper, high frequency Korotkoff sounds come from resonant motion of the arterial wall, which begins after the artery transitions from a buckled state to an expanding state. The motion of one mass, two nonlinear springs, and one damper, driven by transmural pressure under the cuff, are used to model and compute the Korotkoff sounds according to principles of classical Newtonian physics. The natural resonance of this springmass-damper system provides a concise, yet rigorous, explanation for the origin of Korotkoff sounds. Fundamentally, wall stretching in expansion requires more force than wall bending in buckling. At cuff pressures between systolic and diastolic arterial pressure, audible vibrations (> 40 Hz) occur during early expansion of the artery wall beyond its zero pressure radius after the outward moving mass of tissue experiences sudden deceleration, caused by the discontinuity in stiffness between bucked and expanded states. The idealized spring-mass-damper model faithfully reproduces the time domain waveforms of actual Korotkoff sounds in humans. Appearance of arterial sounds occurs at or just above the level of systolic pressure. Disappearance of arterial sounds occurs at or just above the level of diastolic pressure. Muffling of the sounds is explained by increased resistance of the artery to collapse, caused by downstream venous engorgement. A simple analytical model can define the physical origin of Korotkoff sounds, suggesting improved mechanical or electronic filters for their selective detection, and confirming the disappearance of the Korotkoff sounds as the optimal diastolic endpoint.

Changes in Office Blood Pressure Control, Augmentation Index, and Liver Steatosis in Kidney Transplant Patients after Successful Hepatitis C Infection Treatment with Direct Antiviral Agents

“…For the present post hoc analysis, the OBP control improvement was defined as the decline of attended office systolic pressure by at least 20 mmHg without pharmacotherapeutic changes or the reduction of antihypertensive treatment due to the BP decline during the follow-up period. The cut-off value (20 mmHg) was established based on doubled maximum measurement error of 10 mmHg [16,17]. Patients were divided into two study subgroups based on the BP control improvement during the follow-up period.…”

Quantitative Comparison of Korotkoff Sound Waveform Characteristics: Effects of Static Cuff Pressures and Stethoscope Positions

“…Statistical significance was determined by using the RMS intensity amplitude (averaged across two sessions) of KorS waveform as the dependent variable, and cuff pressure, stethoscope circumferential position and longitudinal position as the three within-subject factors. Three-way analysis of variance (ANOVA) with repeated measurements indicated a significant effect on RMS intensity amplitude of stethoscope circumferential position (F [3,87] It is noted that when taking all intensity amplitude into consideration, those measured at cuff pressure P MEDIUM were larger than those at P HIGH or P LOW . Figure 7 shows the measurement of RMS intensity amplitude (averaged across two sessions) of KorS waveform across all conditions.…”

“…Statistical significance was determined by using the high-level duration (averaged across two sessions) of KorS waveform as the dependent variable, and cuff pressure, stethoscope circumferential position and longitudinal position as the three within-subject factors. Three-way ANOVA with repeated measurements indicated a significant effect on high-level duration of KorS of stethoscope circumferential position (F [3,87] = 33.74, p < 0.001), stethoscope longitudinal position (F[2, 58] = 18.84, p < 0.001) and cuff pressure (F[2, 58] = 92.36, p < 0.001). Noted that when taking all conditions into consideration, most high-level durations with cuff pressure P MEDIUM were shorter than those measured at cuff pressure P HIGH or P LOW in Figure 8.…”

“…But Babbs proposed that KorS is produced from the resonant motion of the arterial wall with deflating cuff pressure. 3 Although the genesis of KorS is not fully understood, investigating the factors influencing KorS waveform features is without doubt physiologically and clinically important. [4][5][6][7] Any potential small KorS feature changes and their associated factors worth further investigation, which would provide fundamental basis to improve BP measurement techniques and accuracy.…”

Development of a Multi-Array Pressure Sensor Module for Radial Artery Pulse Wave Measurement

“…In addition, there is a limitation they cannot be used in daily life, therefore, indirect blood pressure measurements such as auscultation or oscillometry have been popularized. Auscultation is a method of estimating blood pressure based on sound, while the method of estimating blood pressure based on vibration is called oscillometry [2]. The auscultation method estimates systolic and diastolic blood pressure based on Korotkoff sounds, while the oscillometry method estimates systolic and diastolic blood pressure using a proprietary formula, measuring the mean arterial pressure at the point where the fluctuation of pressure in the cuff caused by the pulsation is maximized [3,4].…”