Blood Pressure Measurement Based on Wavelet Analysis and Fuzzy Inference Method

Equipment, physiologic, and technique factors can influence the accuracy of blood pressure measurement. The current study was designed to isolate certain technique factors and then assess the accuracy of nursing personnel measurements of blood pressure in three residency family practice centers. An experienced registered nurse was trained in applying the American Heart Association recommendations for determining blood pressure by sphygmomanometry; three 1.5-hour practice sessions demonstrated her accuracy. Nine full days were then spent in the family practice centers rechecking as many staff blood pressure readings as possible while controlling for confounding variables. The following findings were significant: (1) the average absolute differences between control and study nurse systolic and diastolic blood pressure readings were 6.2 mmHg and 4.7 mmHg, respectively; (2) a unidirectional error of 3.8 mmHg in the measurement of diastolic blood pressure was found in one center, possibly because less care was taken with afternoon measurements; (3) variability in systolic blood pressure readings was higher in all three centers (+/- 8.5 mmHg) than attained during the training sessions for the control nurse (+/- 5.8 mmHg); (4) the average errors attributable to technique factors studied that were potentially correctable by training were only 1.8 mmHg for systolic and 0.7 mmHg for diastolic pressures. The degree of inaccuracy in ambulatory nursing blood pressure readings attributable to errors in technique is quantified by this study. Training can reduce, but not abolish, this inaccuracy. Careful attention to proper blood pressure measurement technique and such variables as equipment calibration is essential for both nursing and physician observers. Taking multiple blood pressure measurements before making clinical decisions can limit the effect of these inaccuracies.

In oscillometry, oscillation amplitudes (OAs) embedded in the cuff pressure are drastically affected by a variety of artifacts and cardiovascular diseases, leading to inaccurate arterial blood pressure (ABP) measurement. The purpose of this paper is to improve the accuracy in the arterial pressure measurement by reducing interference in the OAs using a recursive weighted regression algorithm (RWRA). This method includes a fuzzy logic discriminator (FLD) and a recursive regression algorithm. The FLD is used to reduce the effect of artifacts caused by measurement motion disturbance or cardiovascular diseases, and to determine the truthfulness of the oscillation pulse. According to the truth degree, the relationship between the cuff pressure and OA is reconstructed using the regression algorithm. Because the regression method must utilize inverse matrix operation, which will be difficult to implement in an automatic or ambulatory monitor, the recursive regression method is proposed to solve this problem. To test the performance of this RWRA, 47 subjects underwent the ABP measurement using both the auscultation and the oscillometry combined with the RWRA. It was found that the average difference between the pooled blood pressures measured by the auscultation and those by the oscillometry combined with the RWRA was found to be only 4.9 mmHg. Clinical results demonstrated that the proposed RWRA is more robust than the traditional curve fitting algorithm (TCFA). We conclude that the proposed RWRA can be applied to effectively improve the accuracy of the oscillometric blood pressure measurement.

In underserved populations, inadequate surveillance and treatment allows hypertension to persist until actual cardiovascular events occur. Thus, we developed an Internet-based telemedicine system to address the suboptimal control of hypertension and other modifiable risk factors. To minimize cost, the subjects used home monitors for blood pressure (BP) measurements and entered these values into the telemedicine system. We hypothesized that patients could accurately measure their BP and transmit these values via a telemedicine system. Inner city and rural subjects (N = 464; 42% African-American or Hispanic) with 10% or greater 10-year risk of cardiovascular disease and with treatable risk factors were randomized into two groups, control group (CG) and telemedicine group (TG). Each subject received a home sphygmomanometer with memory. The TG recorded and entered BP at least weekly. During office visits, the BP meters were downloaded and recorded BP compared to BP values transmitted via telemedicine. The telemedicine (T) BP values were similar to the meter recorded (R) values (T: systolic/diastolic BP 133.4 +/- 11.1/77.5 +/- 6.8 mm Hg, and R: systolic/diastolic BP 136.4 +/- 11.9.4/79.7 +/- 7.5 mm Hg). The percent error was <1% for both systolic (-0.02 +/- 0.04%) and diastolic (-0.03 +/- 0.04%) BP. Lastly, the telemedicine BP values were similar to the office (O) BP values for systolic and diastolic BP (T: systolic/diastolic BP 133.4 +/- 11.1/77.5 +/- 6.8 mm Hg, and O: systolic/diastolic BP 136.3 +/- 20.5/78.1 +/- 10.5 mm Hg). In underserved populations, this inexpensive approach of patients using a home monitor and entering these values into a telemedicine system provided accurate BP data.

ABSTRACT: In the Cardiovascular Risk in Young Finns project, blood pressure (BP) was measured in 3549 randomly selected children aged 6–18 y in 1980, and 2887 and 2500 of the same individuals in 1983 and 1986, respectively. An ordinary mercury sphygmomanometer (OMS) was used in the first two surveys and a randomzero sphygmomanometer (RZS) in the third survey. Systolic and diastolic BP were lower when measured with an RZS than with an OMS and the shape of the age-related BP curve obtained with an RZS was significantly different from that obtained with an OMS, because low BP values were apparently measured more accurately with the former. Use of the RZS did not affect the distribution of the BP values. Rose's tape readings were used to evaluate the effect of training and to control the accuracy of the BP measurements. According to Rose's tape readings, Korot-koff s 4th phase BP was more difficult to measure accurately than 5th phase (p = 0.002). The mean values for the differences between the correct and actual BP readings on the Rose's tape were —1.2 mm Hg (SD 2.1) for systolic BP, 8.3 mm Hg (SD 13.6) for diastolic Korotkoffs 4th phase BP, and 1.2 mm Hg (SD 7.0) for diastolic Korotkoff's 5th phase BP, with a negative value indicating that the BP phase was measured lower than the correct value. Terminal digit preference was present in each survey to such an extent that it could have hampered the reaching of reliable conclusions from the data obtained with an OMS. The bias caused by terminal digit preference was obviated by the RZS. Our results support the use of an RZS in BP surveys in children, because accurate measures for low BP are best achieved by RZS and because it is the only means of eliminating a major source of observer bias, terminal digit preference. Rose's tape is useful in evaluating the accuracy of BP measurements and in training.

Hypertension Editors' Picks: Preeclampsia, Pregnancy, and Hypertension.

Accurately measuring blood pressure is imperative for diagnosis and control of hypertension. There is a range of devices and methods for measuring blood pressure that each have advantages and limitations. To ensure accuracy of blood pressure measurement and hypertension diagnosis, clinicians and patients should use an accurate and validated blood pressure measurement device, an appropriately sized cuff, and take several measurements rather than only one measurement, using a standardised measurement protocol. Out-of-clinic measurement, using an ambulatory or home blood pressure monitoring device, depending on patient preference, should be used to confirm diagnosis and guide treatment of hypertension. There are emerging new technologies for blood pressure measurement (e.g. wearable technologies) that are yet to be validated and have the potential to improve blood pressure monitoring and patient self-management.

This study explored whether simulation-based education (SBE) could improve the blood pressure (BP) measurement accuracy of first-year clinical technology students. This study was underpinned by constructivist learning theory, which emphasises that learners actively build knowledge through experience and reflection, particularly in realistic and context-rich environments. The study retrospectively examined data from 51 first-year students. Initially, students were taught using conventional training methods such as lectures and tutorials. The same students were then exposed to a one-hour simulation session. After the traditional and simulation sessions, the accuracy of the students’ blood pressure measurements was assessed using a high-fidelity simulation manikin. BP readings measured within ±5 mm Hg of the preset BP were deemed accurate. The McNemar test (p &lt; 0.05) was used to compare results before and after the simulation sessions. Before the SBE session, accuracy for systolic, diastolic, and combined BP measurements was 17.6%, 21.6%, and 3.9%, respectively. After the SBE session, accuracy improved to 45.1% for systolic, 37.3% for diastolic, and 19.6% for combined readings. These improvements suggest that SBE had a positive impact on students’ measurement accuracy of non-invasive BP. The results indicate that incorporating SBE into clinical technology student training may strengthen practical skills and improve readiness for clinical placements. The study further highlights the benefits of simulation through empirical evidence by contributing to the growing body of scholarship on SBE. By offering a hands-on addition to theory-heavy methods, SBE appears to help students bridge the gap between theory and clinical practice—something traditional approaches may not always achieve.

Wood is a natural derivative, it possesses randomly distributed inherent defects all over its mass. This complicates the cost estimation process; data collected showed that even planks with similar defect pattern would have different percentage of material loss. Such uncertain loss was caused by changes in cutting parameters. In this study, a Fuzzy Inference (FI) method was employed to predict wood loss in a rubber wooden toy manufacturing cutting process. Notable variables are: length of cut, and area of cut. Prediction accuracy from the FI method was compared with that of other alternative methods. Common practice assumes a constant defective proportion, resulting in inaccurate cost estimation. A regression equation allows the loss to be varied by the cutting parameters; but only one parameter was found to be significant. Experimental results show that the FI method greatly outperformed regression and conventional methods. These findings emphasize the influence of cutting parameters on product cost. Accurate cost estimation enables better planning for efficient pricing strategies and enhances business competitiveness.

Cardiovascular diseases are one of the most common causes of death; however, the early detection of patients at high risk of sudden cardiac death (SCD) remains an issue. The aim of this study was to analyze the cardio-vascular couplings based on heart rate variability (HRV) and blood pressure variability (BPV) analyses in order to introduce new indices for noninvasive risk stratification in idiopathic dilated cardiomyopathy patients (IDC). High-resolution electrocardiogram (ECG) and continuous noninvasive blood pressure (BP) signals were recorded in 91 IDC patients and 49 healthy subjects (CON). The patients were stratified by their SCD risk as high risk (IDCHR) when after two years the subject either died or suffered life-threatening complications, and as low risk (IDCLR) when the subject remained stable during this period. Values were extracted from ECG and BP signals, the beat-to-beat interval, and systolic and diastolic blood pressure, and analyzed using the segmented Poincaré plot analysis (SPPA), the high-resolution joint symbolic dynamics (HRJSD) and the normalized short time partial directed coherence methods. Support vector machine (SVM) models were built to classify these patients according to SCD risk. IDCHR patients presented lowered HRV and increased BPV compared to both IDCLR patients and the control subjects, suggesting a decrease in their vagal activity and a compensation of sympathetic activity. Both, the cardio -systolic and -diastolic coupling strength was stronger in high-risk patients when comparing with low-risk patients. The cardio-systolic coupling analysis revealed that the systolic influence on heart rate gets weaker as the risk increases. The SVM IDCLR vs. IDCHR model achieved 98.9% accuracy with an area under the curve (AUC) of 0.96. The IDC and the CON groups obtained 93.6% and 0.94 accuracy and AUC, respectively. To simulate a circumstance in which the original status of the subject is unknown, a cascade model was built fusing the aforementioned models, and achieved 94.4% accuracy. In conclusion, this study introduced a novel method for SCD risk stratification for IDC patients based on new indices from coupling analysis and non-linear HRV and BPV. We have uncovered some of the complex interactions within the autonomic regulation in this type of patient.

This study explored the effect of heart rate (HR) on the stability and accuracy of blood pressure (BP) measurement and the optimal HR range for the most accurate blood pressure measurement in atrial fibrillation (AF) patients. A total of 583 patients (383 and 200 with AF and sinus rhythm (SR), respectively) were included in this study. The noninvasive blood pressure (NIBP), invasive blood pressure (IBP), and HR were repeatedly measured ten times at 30-second intervals for every patient. Both the AF and SR groups were then subdivided into five groups depending on the HR (i.e., < 60, 60-80, 80-100, 100-120, and ≥120 bpm). The difference between the IBP and NIBP (i.e., △SBP) and the coefficient of variation (CV) were calculated, and the stability and accuracy of NIBP measurements were analyzed. CV and △SBP were significantly higher in the AF group. In the AF group, the CV of NIBP was highest when the HR was ≥ 100 bpm; and △SBP was significantly lower in the HR groups with 60-80 and 80-100 bpm (< 60 bpm, △SBP 11.62 ± 2.64 mmHg; 60-80 bpm, △SBP 7.10 ± 1.92 mmHg; 80-100 bpm, △SBP 7.10 ± 2.95 mmHg; 100-120 bpm, △SBP 10.52 ± 2.72 mmHg; ≥120 bpm, △SBP 14.15 ± 3.61 mmHg, P < 0.05). The stability and accuracy of the NIBP in the SR groups were not affected by the HR. In AF patients, the NIBP stability was low when the HR was high, and the NIBP was often underestimated when the HR was high or low. Sixty to 100 bpm is the best HR range for measuring blood pressure in AF patients.

The purpose of this work is to discuss the ability of wavelet analysis and cross-spectral algorithm to follow up the short-term cardiovascular function changes during cardiac arrhythmia. It was analyzed the (a) coherence between systolic blood pressure (SBP) and cardiac oscillations in low frequency (LF) and high frequency (HF) band; (b) fluctuations of phase; (c) heart rate variability (HRV) and blood pressure variability (BPV) as a LF power and HF power in frequency and time frequency domain. The analysis was performed on blood pressure and electrocardiogram signals from one rabbit anaesthetized, paralyzed and mechanically ventilated with self-terminating atrial and ventricular fibrillation after 7 minutes of cardiac arrhythmia. Arrhythmia was preceded by a) decreased coherence; b) increase in fluctuations of phase between signals; c) increased spectral energy associated with respiratory frequency in blood pressure signal; d) increased sympathetic outflow to the heart and e) decreased HRV. Cardiac arrhythmia was characterized mainly by increased LF power in blood pressure and cardiac signal. During self-termination of dysrhythmia a larger increased in total BPV and HRV was recorded. These results suggest that important information about both neuronal cardio-circulatory control and risk for spontaneous arrhythmia might be provided by combined analysis of frequency, phase, time-frequency analysis of blood pressure and cardiac oscillation.

Caregiver resources

The article describes the telemedicine system for home monitoring of blood pressure, which allows patients with arterial hypertension to provide remote diagnosis of their current health status. Due to the analysis of existing methods of blood pressure monitoring, the necessity of realization of the system for blood pressure measurement based on the modified oscillometric method was substantiated, the structural diagram of device intended for autonomous recording of human pressure signals by oscillometric method was developed. Proposed algorithm for determination of blood pressure values uses the maximum amplitude algorithm and an algorithm based on the neural networks. The presented algorithms are implemented in the MAILAB software. The results of their approbation on the signals obtained from the developed device have shown the efficiency of the algorithm using neural network technology, especially when processing distorted pressure signals, which allows increasing the accuracy of blood pressure measurement in people with disabilities of cardio-vascular system.

Recent guidelines suggest that Korotkoff sounds can be enhanced by elevating the arm overhead for 30 s before inflating the cuff, and then bringing the arm to the usual position to continue the blood pressure measurement. We evaluated the effect of this manoeuvre on the loudness of the Korotkoff sound and on the accuracy of Riva-Rocci-Korotkoff (RRK) measurements. Using an electronic stethoscope, we compared the amplitudes of Korotkoff sounds between both arm positions. To determine the accuracy of blood pressure measurements, which are performed after raising the arm first, we validated this 'new method' of blood pressure measurement according to the British Hypertension Society protocol. The amplitude of the first Korotkoff sound with the arm elevated overhead for 30 s first, was 1.82+/-1.75 times greater (P<0.01) than the amplitude of the first Korotkoff sound with the arm in the usual position. Second and third Korotkoff sounds were also louder. RRK blood pressure measurements that were performed after raising the arm overhead for 30 s did pass the validation procedure according to the British Hypertension Society protocol. The nonsignificant difference (RRK after raising the arm first-normal RRK measurements) was 0.33+/-2.85 mmHg for systolic and -1.17+/-2.63 mmHg for diastolic measurements. Korotkoff sounds can be enhanced by elevating the arm overhead for 30 s before inflating the cuff, and then bringing the arm to the usual position to continue in the blood pressure measurement. This manoeuvre leads to louder systolic Korotkoff sounds and does not have an effect on measured blood pressure levels.

Blood pressure (BP) measurement accuracy depends on consistent changes in Korotkoff sounds (KorS) for manual measurement and oscillometric pulses for automated measurement, yet little is known about the direct effect of respiration on these physiological signals. The aim of this research was to quantitatively assess the modulation effect of respiration on Korotkoff sounds and oscillometric pulses. Systolic and diastolic blood pressures were measured manually from 30 healthy subjects (age 41 ± 12 years). Three static cuff pressure conditions were studied for two respiratory rates. Cuff pressure [with oscillometric pulses (OscP)], ECG, chest motion respiration [respiration signal (Resp), from magnetometer] and Korotkoff sounds (KorS, from digital stethoscope) were recorded twice for 20 s. The physiological data were evenly resampled. Respiratory frequency was calculated from Resp (fR), OscP (fO) and KorS (fK) from peak spectral frequency. There was no statistically significant difference between fR and fO or fK. Respiratory modulation was observed in all subjects. OscP amplitude modulation changed significantly between the two respiratory rates (p < 0.05) and between the three cuff pressures (p < 0.0001), and decreased significantly with decreasing cuff pressure (p < 0.05). The phase shift between Resp and modulation of OscP was statistically significant with respiratory rates (p < 0.05), but not with cuff pressures. It is accepted that BP in individuals is variable and that this relates to respiration; we now show that this respiration modulates oscillometric pulse and Korotkoff sound amplitudes from which BP is measured.