2 research outputs found
User-friendly single-lead ECG device for home telemonitoring applications
Chronic Heart Failure is a chronic disease that often leads to frequent hospitalizations of patients, with consequences on their quality of life and on the expense sustained by the Health System. Enabling early diagnosis through a frequent monitoring performed directly by the patients can improve the management of such disease. This paper introduces a user-friendly single-lead ECG device conceived to be easily used at home by affected patients. The device requires few basic actions to be operated and it is able to send transparently the acquired ECG to the designated service centre exploiting a Bluetooth connection with an Internet gateway. © 2014 IEEE
Assessment of trends in the cardiovascular system from time interval measurements using physiological signals obtained at the limbs
Cardiovascular diseases are an increasing source of concern in modern societies due to their increasing prevalence and high impact on the lives of many people. Monitoring cardiovascular parameters in ambulatory scenarios is an emerging approach that can provide better medical access to patients while decreasing the costs associated to the treatment of these diseases.
This work analyzes systems and methods to measure time intervals between the electrocardiogram (ECG), impedance plethysmogram (IPG), and the ballistocardiogram (BCG), which can be obtained at the limbs in ambulatory scenarios using simple and cost-effective systems, to assess cardiovascular intervals of interest, such as the pulse arrival time (PAT), pulse transit time (PTT), or the pre-ejection period (PEP).
The first section of this thesis analyzes the impact of the signal acquisition system on the uncertainty in timing measurements in order to establish the design specifications for systems intended for that purpose. The minimal requirements found are not very demanding yet some common signal acquisition systems do not fulfill all of them while other capabilities typically found in signal acquisition systems could be downgraded without worsening the timing uncertainty. This section is also devoted to the design of systems intended for timing measurements in ambulatory scenarios according to the specifications previously established. The systems presented have evolved from the current state-of-the-art and are designed for adequate performance in timing measurements with a minimal number of active components.
The second section is focused on the measurement of time intervals from the IPG measured from limb to limb, which is a signal that until now has only been used to monitor heart rate. A model to estimate the contributions to the time events in the measured waveform of the different body segments along the current path from geometrical properties of the large arteries is proposed, and the simulation under blood pressure changes suggests that the signal is sensitive to changes in proximal sites of the current path rather than in distal sites. Experimental results show that the PAT to the hand-to-hand IPG, which is obtained from a novel four-electrode handheld system, is correlated to changes in the PEP whereas the PAT to the foot-to-foot IPG shows good performance in assessing changes in the femoral PAT. Therefore, limb-to-limb IPG measurements significantly increase the number of time intervals of interest that can be measured at the limbs since the signals deliver information from proximal sites complementary to that of other measurements typically performed at distal sites.
The next section is devoted to the measurement of time intervals that involve different waves of the BCG obtained in a standing platform and whose origin is still under discussion. From the relative timing of other physiological signals, it is hypothesized that the IJ interval of the BCG is sensitive to variations in the PTT. Experimental results show that the BCG I wave is a better surrogate of the cardiac ejection time than the widely-used J wave, which is also supported by the good correlation found between the IJ interval and the aortic PTT. Finally, the novel time interval from the BCG I wave to the foot of the IPG measured between feet, which can be obtained from the same bathroom scale than the BCG, shows good performance in assessing the aortic PAT. The results presented reinforce the role of the BCG as a tool for ambulatory monitoring since the main time intervals targeted in this thesis can be obtained from the timing of its waves.
Even though the methods described were tested in a small group of subjects, the results presented in this work show the feasibility and potential of several time interval measurements between the proposed signals that can be performed in ambulatory scenarios, provided the systems intended for that purpose fulfill some minimal design requirements.Les malalties cardiovasculars sĂłn una tema de preocupaciĂł creixent en societats modernes, degut a l’augment de la seva prevalença i l'elevat impacte en les vides dels pacients que les sofreixen. La mesura i monitoratge de parĂ metres cardiovasculars en entorns ambulatoris Ă©s una prĂ ctica emergent que facilita l’accĂ©s als serveis mèdics i permet reduir drĂ sticament els costos associats al tractament d'aquestes malalties. En aquest treball s’analitzen sistemes i mètodes per la mesura d’intervals temporals entre l’electrocardiograma (ECG), el pletismograma d’impedĂ ncia (IPG) i el balistocardiograma (BCG), que es poden obtenir de les extremitats i en entorns ambulatoris a partir de sistemes de baix cost, per tal d’avaluar intervals cardiovasculars d’interès com el pulse arrival time (PAT), pulse transit time (PTT) o el pre-ejection period (PEP). En la primera secciĂł d'aquesta tesi s’analitza l’impacte del sistema d’adquisiciĂł del senyal en la incertesa de mesures temporals, per tal d’establir els requeriments mĂnims que s’han de complir en entorns ambulatoris. Tot i que els valors obtinguts de l’anĂ lisi no sĂłn especialment exigents, alguns no sĂłn assolits en diversos sistemes habitualment utilitzats mentre que altres solen estar sobredimensionats i es podrien degradar sense augmentar la incertesa en mesures temporals. Aquesta secciĂł tambĂ© inclou el disseny i proposta de sistemes per la mesura d’intervals en entorns ambulatoris d’acord amb les especificacions anteriorment establertes, a partir de l’estat de l’art i amb l’objectiu de garantir un correcte funcionament en entorns ambulatoris amb un nombre mĂnim d’elements actius per reduir el cost i el consum. La segona secciĂł es centra en la mesura d’intervals temporals a partir de l’IPG mesurat entre extremitats, que fins al moment nomĂ©s s’ha fet servir per mesurar el ritme cardĂac. Es proposa un model per estimar la contribuciĂł de cada segment arterial per on circula el corrent a la forma d’ona obtinguda a partir de la geometria i propietats fĂsiques de les artèries, i les simulacions suggereixen que la senyal entre extremitats Ă©s mĂ©s sensible a canvis en arteries proximals que en distals. Els resultats experimentals mostren que el PAT al hand-to-hand IPG, obtingut a partir d’un innovador sistema handheld de quatre elèctrodes, estĂ fortament correlacionat amb els canvis de PEP, mentre que el PAT al foot-to-foot IPG estĂ correlat amb els canvis en PAT femoral. ConseqĂĽentment, l’ILG entre extremitats augmenta de manera significativa els intervals d’interès que es poden obtenir en extremitats degut a que proporciona informaciĂł complementĂ ria a les mesures que habitualment s’hi realitzen. La tercera secciĂł estĂ dedicada a la mesura d’intervals que inclouen les ones del BCG vertical obtingut en plataformes, de les que encara se’n discuteix l’origen. A partir de la posiciĂł temporal relativa respecte altres ones fisiològiques, s’hipostatitza que l’interval IJ del BCG es sensible a variacions del PTT. Els resultats experimentals mostren que la ona I del BCG Ă©s un millor indicador de l’ejecciĂł cardĂaca que el pic J, tot i que aquest Ă©s el mĂ©s utilitzat habitualment, degut a la bona correlaciĂł entre l’interval IJ i el PTT aòrtic. Finalment, es presenta un mètode alternatiu per la mesura del PTT aòrtic a partir de l’interval entre el pic I del BCG i el peu del foot-to-foot IPG, que es pot obtenir de la mateixa plataforma que el BCG i incrementa la robustesa de la mesura. Els resultats presentats reforcen el paper del BCG com a en mesures en entorns ambulatoris, ja que els principals intervals objectiu d’aquesta tesi es poden obtenir a partir de les seves ones. Tot i que els mètodes descrits han estat provats en grups petits de subjectes saludables, els resultats mostren la viabilitat i el potencial de diversos intervals temporals entre les senyals proposades que poden Ă©sser realitzats en entorns ambulatoris, sempre que els sistemes emprats compleixin els requisits mĂnims de disseny.Postprint (published version