Mengsun Yu

Improving Auscultatory Blood Pressure Measurement With Electronic and Computer Technology: The Visual Auscultation Method

BACKGROUND The auscultatory method is used as the reference standard in all prevalent protocols for validation of noninvasive blood pressure measuring devices, and a validation study is essentially based on the comparison between the device and observer measurements. Thus, the objectivity and accuracy of observer measurements are crucial to the validation result. METHODS To provide observers with more objective information about an auscultatory measurement so that sufficient information to make measurements with greater potential objectivity and accuracy can be available, a computerized data acquisition and analysis system has been developed. It cannot only acquire and store Korotkoff sound, cuff pressure, and oscillometric pulse signals, as well as the sphygmomanometer image, but it also can display the waveforms of the three signals and the sphygmomanometer video while playing the synchronous Korotkoff sounds. With this system, observers can make their measurements via the visual auscultation method, that is to say, by watching those waveforms, instead of the sphygmomanometer, while listening for synchronized Korotkoff sounds. The system was validated according to the International Protocol (IP). RESULTS The result showed that all the differences between system measurements by the visual auscultation method and observer measurements by the conventional auscultatory method were within 4 mm Hg. CONCLUSIONS The visual auscultation method achieved a high degree of accuracy, and human observers can be replaced by the system in the validation study of blood pressure measuring devices.

Noninvasive measurement of beat-to-beat arterial blood pressure by the Korotkoff sound delay time.

ObjectiveTo propose a novel noninvasive beat-to-beat arterial blood pressure measurement method based on the Korotkoff sound delay time (KDT) and evaluate its accuracy in preliminary experiments. MethodsKDT decreases as the cuff pressure P deflates, which can be described by a function KDT=f (P). Actually, KDT is a function of arterial transmural pressure. Therefore, the variation in blood pressure can be obtained by the transmural pressure, which is estimated by the KDT. Holding the cuff pressure at an approximate constant pressure between systolic pressure and diastolic pressure, the variation in blood pressure &Dgr;EBP between successive heartbeats can be estimated according to KDT and f′(p), which represents the variation of KDT corresponding to unit pressure. Then the blood pressure for each heartbeat can be obtained by accumulating the &Dgr;EBP. Invasive and noninvasive blood pressure values of six participants were measured simultaneously to evaluate the method. ResultsThe average of the correlation coefficients between the invasive mean arterial pressure (MAP) and the KDT for six participants was −0.91. The average of the correlation coefficients between the invasive MAP and the estimated mean blood pressure (EBP) was 0.92. The mean difference between EBP and MAP was 0.51 mmHg, and the SD was 2.65 mmHg. The mean blood pressure estimated by the KDT is consistent with the invasive MAP. ConclusionThe beat-to-beat blood pressure estimated by KDT provides an accurate estimate of MAP in the preliminary experiments and represents a potential acceptable alternative to invasive blood pressure monitoring during laboratory studies.

Detection of genioglossus myoelectric activity using ICA of multi-channel mandible sEMG.

BACKGROUND Genioglossus myoelectric activity is of great significance in evaluating clinical respiratory function. However, there is a tradeoff in genioglossus EMG measurement with respect to accuracy versus convenience. OBJECTIVE This paper presents a way to separate the characteristics of genioglossus myoelectric activity from multi-channel mandible sEMG through independent component analysis. METHODS First, intra-oral genioglossus EMGgenioglossus EMG and three-channel mandible sEMG were recorded simultaneously. The FastICA algorithm was applied to three independent components from the sEMG signals. Then the independent components with the intra-oral genioglossus EMG were compared by calculating the Pearson correlation coefficient between them. RESULTS An examination of 60 EMG samples showed that the FastICA algorithm was effective in separating the characteristics of genioglossus myoelectric activity from multi-channel mandible sEMG. The results of analysis were coincident with clinical diagnosis through intra-oral electrodes. CONCLUSIONS Genioglossus myoelectric activity can be evaluated accurately by multi-channel mandible sEMG, which is non-invasive and easy to record.

A simplified computer model of cardiovascular system with an arm branch.

Non-invasive pressure simulators that regenerate oscillometric waveforms promise an alternative to expensive clinical trials for validating oscillometric noninvasive blood pressure devices. However, existing simulators only provide oscillometric pressure in cuff and thus have a limited accuracy. It is promising to build a physical simulator that contains a synthetic arm with a built-in brachial artery and an affiliated hydraulic model of cardiovascular system. To guide the construction of this kind of simulator, this paper presents a computer model of cardiovascular system with a relatively simple structure, where the distribution of pressures and flows in aorta root and brachial artery can be simulated, and the produced waves are accordant with the physical data. This model can be used to provide the parameters and structure that will be needed to build the new simulator.

A Novel Method for Korotkoff Vibration Blood Pressure Measurement Based on Oscillometric

The aim of this study is to confirm systolic blood pressure(SBP) and diastolic blood pressure(DBP) based on oscillometric method. The approach can get an accurate MAP, accessible to SBP and DBP simultaneously using Korotkoff vibration instead of the traditional sound signal. Experiments were conducted on healthy, non-smoking and normotensive subjects. The cuff pressure, Korotkoff vibration, oscillometric pulse and radial pulse were recorded, the auscultation was carried out by a doctor synchronously. SBP and DBP were calculated by identifying the feature points of Korotkoff vibration. The measurement value obtained by this approach was greater than the result based on auscultatory sphygmomanometry. The mean difference (ME) and standard deviation (SD) of SBP and DBP were 0.59±3.84 mmHg and 4.77 ±3.52 mmHg respectively. The correlation coefficients of SBP and DBP are 0.96, 0.93. The experiment indicates that this approach has a great feasibility as a noninvasive BP measurement means.

Determination of delay time in individual transfer function for central aortic pressure reconstruction

In previous research, time-delay (Δt) was a more important parameter than the reflection coefficient in the individual transfer function of central aortic pressure reconstruction. The Δt can be obtained by electrocardiography (ECG) or phonocardiography (PCG). Because the pre-ejection period remains an uncertain factor, the present study used ECG and PCG to define the delay time and analyzed the accuracy of the reconstruction results. The Δtpre is the actual delay time derived from the aorta to the carotid pressure wave, ΔtPCG is the time delay between the aortic valve component of the second heart sound and the dicrotic incisura of the carotid pressure wave, and ΔtECG represents the delay from the interval of the ECG R-peak to the foot of the carotid pressure wave. Compared with the measured aortic pressure, the reconstruction result obtained by Δt=ΔtPCG slightly differed from the best result estimated by Δt=Δtpre. However, the differences between the result obtained by Δt=ΔtECG and the best result were significant in terms of the diastolic blood pressure, and pulse pressure, and especially in terms of the augmentation index and root-mean-square-error. Thus, the Δt should be determined by PCG for central aortic pressure reconstruction in practice.