Advanced indirect method for measuring blood pressure

Presently existing blood pressure meters require trained operator otherwise do not assure accurate measurement. An easy-to-use and accurate device would help the early detection of hypertonia as well as self-monitoring at home. This latter would mean an effective aid for the general practitioner to monitor the patient; providing a feedback for treatment and medication. The paper presents the results of the research work having been carried out for an indirect blood pressure measurement procedure in the Biomedical Engineering Laboratory of the Department of Measurement and Information Systems, Budapest University of Technology and Economics. The procedure improves the classical oscillometric algorithm and identifies improperly placed cuff. It was incorporated into eight home health monitoring devices that were used for three months by patients with cardiovascular diseases. More than 1000 recordings of patients and more than 500 of healthy control subjects have been analyzed. The presented algorithm has been va lidated by means of a non-invasive blood pressure meter tester. The bulk of the 100 tester records we have made simulates some kind of artifact or cardiovascular disease

A method for extracting respiratory frequency during blood pressure measurement, from oscillometric cuff pressure pulses and Korotkoff sounds recorded during the measurement

Respiratory frequency is an important physiological feature commonly used to assess health. However, the current measurements involve dedicated devices which not only increase the medical cost but also make health monitoring inconvenient. Earlier studies have shown that respiratory frequency could be extracted from electrocardiography (ECG) signal, but little was done to assess the possibility of extracting respiratory frequency from oscillometric cuff pressure pulses (OscP) or Korotkoff sounds (KorS), which are normally used for measuring blood pressure and more easily accessible than the ECG signal. This study presented a method to extract respiratory frequency from OscP and KorS during clinical blood pressure measurement. The method was evaluated with clinical data collected from 15 healthy participants, and its measurement accuracy was compared with a reference respiratory rate obtained with a magnetometer. Experimental results showed small non-significant mean absolute bias (0.019 Hz for OscP and 0.024 Hz for KorS) and high correlation (0.7 for both OscP and KorS) between the reference respiratory frequency and respiratory frequency extracted from OscP or KorS, indicating the high reliability of extracting respiratory frequency from OscP and KorS during normal blood pressure measurement

Cuffless bood pressure estimation

L'hypertension est une maladie qui affecte plus d'un milliard de personnes dans le monde. Il s'agit d'une des principales causes de décès; le suivi et la gestion de cette maladie sont donc cruciaux. La technologie de mesure de la pression artérielle la plus répandue, utilisant le brassard pressurisé, ne permet cependant pas un suivi en continu de la pression, ce qui limite l'étendue de son utilisation. Ces obstacles pourraient être surmontés par la mesure indirecte de la pression par l'entremise de l'électrocardiographie ou de la photopléthysmographie, qui se prêtent à la création d'appareils portables, confortables et peu coûteux. Ce travail de recherche, réalisé en collaboration avec le département d'ingénierie biomédicale de l'université de Lund, en Suède, porte principalement sur la base de données publique Multiparameter Intelligent Monitoring in Intensive Care (MIMIC) Waveform Datasetde PhysioNet, largement utilisée dans la littérature portant sur le développement et la validation d'algorithmes d'estimation de la pression artérielle sans brassard pressurisé. Puisque ces données proviennent d'unités de soins intensifs et ont été recueillies dans des conditions non contrôlées, plusieurs chercheurs ont avancé que les modèles d'estimation de la pression artérielle se basant sur ces données ne sont pas valides pour la population générale. Pour la première fois dans la littérature, cette hypothèse est ici mise à l'épreuve en comparant les données de MIMIC à un ensemble de données de référence plus représentatif de la population générale et recueilli selon une procédure expérimentale bien définie. Des tests statistiques révèlent une différence significative entre les ensembles de données, ainsi qu'une réponse différente aux changements de pression artérielle, et ce, pour la majorité des caractéristiques extraites du photopléthysmogramme. De plus, les répercussions de ces différences sont démontrées à l'aide d'un test pratique d'estimation de la pression artérielle par apprentissage machine. En effet, un modèle entraîné sur l'un des ensembles de données perd en grande partie sa capacité prédictive lorsque validé sur l'autre ensemble, par rapport à sa performance en validation croisée sur l'ensemble d'entraînement. Ces résultats constituent les contributions principales de ce travail et ont été soumis sous forme d'article à la revue Physiological Measurement. Un volet additionnel de la recherche portant sur l'analyse du pouls par décomposition (pulse de composition analysis ou PDA) est présenté dans un deuxième temps. La PDA est une technique permettant de séparer l'onde du pouls en une composante excitative et ses réflexions, utilisée pour extraire des caractéristiques du signal dans le contexte de l'estimation de la pression artérielle. Les résultats obtenus démontrent que l'estimation de la position temporelle des réflexions à partir de points de référence de la dérivée seconde du signal donne d'aussi bons résultats que leur détermination par la méthode traditionnelle d'approximation successive, tout en étant beaucoup plus rapide. Une méthode récursive rapide de PDA est également étudiée, mais démontrée comme inadéquate dans un contexte de comparaison intersujet.Hypertension affects more than one billion people worldwide. As one of the leading causes of death, tracking and management of the condition is critical, but is impeded by the current cuff-based blood pressure monitoring technology. Continuous and more ubiquitous blood pressure monitoring may be achieved through simpler, cheaper and less invasive cuff-less devices, performing an indirect measure through electrocardiography or photoplethysmography. Produced in collaboration with the department of biomedical engineering of Lund Universityin Sweden, this work focuses on public data that has been widely used in the literature to develop and validate cuffless blood pressure estimation algorithms: The Multiparameter Intelligent Monitoring in Intensive Care (MIMIC) Waveform Dataset from PhysioNet. Because it is sourced from intensive care units and collected in absence of controlled conditions, it has many times been hypothesized that blood pressure estimation models based on its data may not generalize to the normal population. This work tests that hypothesis for the first time by comparing the MIMIC dataset to another reference dataset more representative of the general population and obtained under controlled experimental conditions. Through statistical testing, a majority of photoplethysmogram based features extracted from MIMIC are shown to differ significantly from the reference dataset and to respond differently to blood pressure changes. In addition, the practical impact of those differences is tested through the training and cross validating of machine learning models on both datasets, demonstrating an acute loss of predictive powers of models facing data from outside the dataset used in the training phase. As the main contribution of this work, these findings have been submitted as a journal paper to Physiological Measurement. Additional original research is also presented in relation to pulse decomposition analysis (PDA), a technique used to separate the pulse wave from its reflections, in the context of blood pressure estimation. The results obtained through this work show that when using the timing of reflections as part of blood pressure predictors, estimating those timings from fiducial points in the second derivative works as well as using the traditional and computationally costly successive approximation PDA method, while being many times faster. An alternative fast recursive PDA algorithm is also presented and shown to perform inadequately in an inter-subject comparison context

Algoritmo para el análisis en conjunto de las señales del ECG y PPG

The main objective of this research is based on finding out some assertive and robust Photoplethysmogram’s PPG & Electrocardiogram’s ECG blood pressure-related parameters by the implementation of a novel method with innovations in signal processing and analysis. The biomedical ECG and PPG signals are recorded using a mobile monitor CardioQVark. To increase the cuffless blood pressure measurement accuracy, a technique that involves not only the ECG and PPG joint parameters extraction but also some individual PPG’s morphology features, is proposed in this work. Firstly, the biomedical ECG and PPG signals are time–frequency filtered.  Secondly, some novel parameters from the morphology of photoplethysmogram signal, which may be correlated with blood pressure, are considered in addition to the pulse transit time. Additionally, a neural network is built to determine the relationship between the estimated and reference blood pressure. Finally, the correlation coefficient and regression line are obtained to evaluate the feasibility.El objetivo de esta investigación consiste en identificar aquellos parámetros provenientes de las señales del electrocardiograma ECG y fotopletismograma PPG que permitan hacer una evaluación de la presión sanguínea utilizando un dispositivo móvil. El método propuesto incluye innovaciones en el procesamiento y análisis de las señales. Con el objetivo de aumentar la precisión de la medición de la presión sanguínea, en este trabajo, se propone la utilización de parámetros provenientes de la señal del PPG en conjunto con el PTT obtenido de las señales del ECG y PPG analizadas en conjunto. Adicionalmente, se propone el diseño e implementación de una red neural para determinar la relación existente entre la presión sanguínea estimada por el método y la de referencia, lo cual permite evaluar la viabilidad del método propuesto

Kriterien einer hydraulisch gekoppelten Gewebedruckkurve am Oberarm zur Ermittlung des systolischen Blutdrucks

Thema: Diese Dissertation beschäftigt sich mit der Analyse einer am Oberarm nicht-invasiv abgeleiteten und hydraulisch gekoppelten Gewebedruckkurve zur Ermittlung des systolischen arteriellen Blutdrucks (SAP). Das hierfür notwendige Medizinprodukt (ShellCuff) wurde von der UP-MED GmbH München entwickelt. Zielsetzung: Durch die Identifikation bestimmter morphologischer Kriterien der Gewebedruckkurve soll eine präzise und zuverlässige Bestimmung des systolischen arteriellen Blutdrucks ermöglicht werden. Patientenkollektiv und Methodik: Die Daten für diese Dissertation wurden perioperativ und intensivmedizinisch von Patienten (n = 52) aus dem neurochirurgischen und abdominalchirurgischen Bereich gewonnen. Als Referenzmessung diente eine aus klinischer Indikation notwendige invasive Blutdruckmessung (über einen Zugang an der A. femoralis). Die Auswertung der Messergebnisse erfolgte durch die Methode nach Bland Altman für multiple Messungen sowie durch eine lineare Regression. Ergebnisse: Eine Auswertung mit 5 Messungen pro Patient (insgesamt 255 Messungen) ergab für den SAP der ShellCuff-Messung eine systematische Messabweichung von -0,9 mmHg, eine Standardabweichung von 5,7 mmHg (oberes LoA 10,2 mmHg, unteres LoA -12,1 mmHg) und ein R2 von 0,9001. Conclusio: Die Bestimmung des SAP durch den ShellCuff ließ sich beim untersuchten Patientenkollektiv mit hoher Präzsion und geringer Standardabweichung realisieren und erfüllt die Vorgaben der DIN EN 1060-3:2010-03 und EN 1060-3:1997+A2:2009 (D) hinsichtlich der systematischen Messabweichung und der Standardabweichung

A model-based calibration method for the design of wearable and cuffless devices measuring arterial blood pressure.

Liu, Yinbo.Thesis (M.Phil.)--Chinese University of Hong Kong, 2008.Includes bibliographical references (leaves 74-79).Abstracts in English and Chinese.Abstract --- p.iList of Figures --- p.ivList of Tables --- p.viiiIntroduction --- p.1Chapter 1.1 --- Current status of Blood Pressure Management --- p.1Chapter 1.2 --- Current Status of Noninvasive Blood Pressure Measurement Techniques --- p.4Chapter 1.3 --- Motivations and Objectives of This Thesis --- p.9Chapter 1.4 --- Organization of This Thesis --- p.9Backgrounds --- p.11Chapter 2.1 --- Principle of the Pulse Transit Time-based Approach for BP Measurement --- p.11Chapter 2.1.1 --- General Descriptions --- p.11Chapter 2.1.2 --- Pressure Wave Propagation in Cylindrical Arteries --- p.13Chapter 2.1.3 --- Determining the PTT for BP Measurement --- p.14Chapter 2.2 --- Backgrounds for Pressure Related Elastic Properties of Artery --- p.17Chapter 2.2.1 --- Transmural Pressure and Its Components --- p.17Chapter 2.2.2 --- Volume-pressure Models --- p.19Chapter 2.2.3 --- Types and Structure of the Artery and Its Properties --- p.20Chapter 2.3 --- Literature Review on the Calibration Methods for Cuffless Blood Pressure Measurements --- p.22Chapter 2.4 --- Section Summary --- p.25Investigations on Factors Affecting PTT or BP --- p.26Chapter 3.1 --- The Effects of External Pressure --- p.26Chapter 3.1.1 --- Background --- p.26Chapter 3.1.2 --- Experimental protocol --- p.28Chapter 3.1.3 --- Analysis for the Effects of External Pressure on PTT --- p.30Chapter 3.1.4 --- Section Discussions --- p.31Chapter 3.2 --- The Effects of Hydrostatic Pressure --- p.32Chapter 3.2.1 --- Experimental protocol --- p.33Chapter 3.2.2 --- Analysis for the Effects of Hydrostatic Pressure on PTT --- p.34Chapter 3.2.3 --- Section Discussions --- p.37Chapter 3.2.4 --- Section Summary --- p.38Modeling the Effect of Hydrostatic Pressure on PTT for A Calibration Method --- p.39Chapter 4.1 --- Current Status of Hydrostatic Calibration Approaches --- p.39Chapter 4.2. --- Modeling Pulse Transit Time under the Effects of Hydrostatic Pressure for A Hydrostatic Calibration Method: --- p.40Chapter 4.2.1 --- Basic BP-PTT model --- p.40Chapter 4.2.2 --- V-P relationship Represented by a Sigmoid Curve --- p.40Chapter 4.2.3 --- Relating PTT with Hydrostatic Pressure --- p.41Chapter 4.2.4 --- Implementing the Hydrostatic Calibration Method for BP Estimation --- p.43Chapter 4.3. --- Preliminary Experiment --- p.44Chapter 4.3.1. --- Experimental Protocol and Methodology --- p.44Chapter 4.3.2. --- Experimental Analysis --- p.46Chapter 4.4. --- Section Discussions --- p.48Chapter 4.5. --- A Novel Implementation Algorithm of Hydrostatic Calibration Method for Cuffless BP Estimation --- p.49Chapter 4.6. --- Section Summary --- p.50Experimental Studies for the Hydrostatic Calibration Approach --- p.51Chapter 5.1 --- Experimental Analysis --- p.51Chapter 5.1.1 --- Experimental Protocol --- p.51Chapter 5.1.2 --- Methodology --- p.53Chapter 5.1.3 --- Preparations --- p.54Chapter 5.1.4 --- Experimental Results --- p.56Chapter 5.2 --- Section Discussions --- p.63Chapter 5.3 --- Section Summary --- p.70Conclusions and Suggestions for Future Works --- p.71Chapter 6.1 --- Conclusions --- p.71Chapter 6.2 --- Suggestions for Future Works --- p.72Reference --- p.7

Regression Based Comparative Study for Continuous BP Measurement Using Pulse Transit Time

Context: Blood Pressure (BP) measurement becomes a vital parameter now days due to the continuous increase in chronic heart diseases worldwide. Existing devices for BP measurement are less portable and also does not support continuous BP measurement. Many studies have been done on non-invasive BP measurement using electrocardiography (ECG) and photoplethysmograph (PPG) waveforms. These methods also clarify accurate results.Calculation of PTT and BP:This study relates BP measured using two PPGs with the existing methods which uses the ECG signals. The cuff and ECG signal can be replaced by PPG sensors as the results acquired using PPG signals gives high accuracy.Basic terms can be defined to relate BP followed by detection of P-base point and ends with the estimation for BP calculations.Proposed Methodology: The algorithm for the proposed technology can be defined and the work shows how the use of wavelet de-noised PPGs can replace the existing ECG based techniques to decrease the complexity of overall devices and also increases the precision level.Results and Discussion: Analysis of all the type of combinations can show the results that minimum error and maximum accuracy can be found when BP is estimated. Conclusion: PTT based on two PPG’s are best among all other methods including the utilization of second order non-linear regression technique