Analysis of coronary angiography related psychophysiological responses

<p>Abstract</p> <p>Background</p> <p>Coronary angiography is an important tool in diagnosis of cardiovascular diseases. However, it is the administration is relatively stressful and emotionally traumatic for the subjects. The aim of this study is to evaluate psychophysiological responses induced by the coronary angiography instead of subjective methods such as a questionnaire. We have also evaluated the influence of the tranquilizer on the psychophysiological responses.</p> <p>Methods</p> <p>Electrocardiography (ECG), Blood Volume Pulse (BVP), and Galvanic Skin Response (GSR) of 34 patients who underwent coronary angiography operation were recorded. Recordings were done at three phases: "1 hour before," "during," and "1 hour after" the coronary angiography test. Total of 5 features obtained from the physiological signals were compared across these three phases. Sixteen of the patients were administered 5 mg of a tranquilizer (Diazepam) before the operation and remaining 18 were not.</p> <p>Results</p> <p>Our results indicate that there is a strong correlation between features (LF/HF, Bk, DN1/DN2, skin conductance level and seg_mean) in terms of reflecting psychophysiological responses. However only DN1/DN2 feature has statistically significant differences between angiography phases (for diazepam: p = 0.0201, for non_diazepam p = 0.0224). We also note that there are statistically significant differences between the diazepam and non-diazepam groups for seg_mean features in "before", "during" and "after" phases (p = 0.0156, 0.0282, and 0.0443, respectively).</p> <p>Conclusions</p> <p>The most intense sympathetic activity is observed in the "during" angiography phase for both of the groups. The obtained features can be used in some clinical studies where generation of the customized/individual diagnoses styles and quantitative evaluation of psychophysiological responses is necessary.</p

Non-invasive discrimination between diabetic states (HBA1C<8% and HBA1C>10%) using photoplethysmography

Diabetes mellitus is a group of metabolic diseases associated with the production and/or reaction of insulin leading to hyperglycemia. Glycated hemoglobin (HbA1c) level is generally measured for hyperglycemia. The risk of developing complications depends on both the duration of diabetes and hyperglycemia. A trend of increasing arterial stiffness has been identified in type 2 diabetes. Photoplethysmographic (PPG) pulse wave provides a ‘window’ into the properties of small arteries whereas stiffening of these arteries will alter the PPG waveform. In this research, the potential of PPG in discriminating between type 2 diabetic patients at risk of having HbA1c level > 10% has been investigated. To this end, PPG signals recorded from diabetic patients with different levels of HbA1c (HbA1c level 10%) were acquired from the index finger of the right arm of 101 subjects (53 subjects with HbA1c level 10%) at a sampling rate of 275 Hz. The area under the curve of PPG (auc-PPG) was proposed in analyzing the PPG pulse contour. Results of t-test analysis show that auc-PPG is significantly larger in diabetic patients with HbA1c level 10% (p-value 10% (total 56 subjects) show that there is no significant difference in the mean value of auc-PPG between the first measurement and repeated measurement for both groups. Finally, a logistic regression model for estimating the risk of having HbA1c level > 10% among diabetic patients was estimated using data from 51 female diabetic patients. The model shows that the auc-PPG is an independent predictor for estimating the risk of having HbA1c level > 10% (p-value = 0.005) among female diabetic patients

Reconocimiento de Estados Afectivos a partir de Señales Biomédicas

Las emociones constituyen una parte fundamental de los individuos, influyendo en sucomunicación diaria, la toma de decisiones y el foco de atención. La incorporación de las emociones en la tecnología ha avanzado en losúltimos años, desde estudios exploratorios en la respuesta a los estímulos, a aplicaciones comerciales en interfaces hombre-máquina. Una de las fuentes paraidentificar estados emocionales es la respuesta fisiológica, registrada medianteseñales biomédicas. El uso de estas señales permitiría el desarrollo de dispositivos poco invasivos, como por ejemplo una pulsera, que puedan registrarseñales continuamente, en diferentes condiciones, y manteniendo la privacidad delos usuarios. Existen numerosos enfoques para el reconocimiento de afectos, condiferentes señales, técnicas de procesamiento de la señal y métodos deaprendizaje automático. Entre ellos, la combinación demúltiples señales se utilizó ampliamente para mejorar las tasas de reconocimiento,pero resulta inviable en la práctica por su invasividad. Los desafíosactuales requieren clasificadores que puedan funcionar en tiempo real, enaplicaciones interactivas, y con mayor comodidad para el usuario. En esta tesis doctoral se aborda el desafío del reconocimiento de estadosafectivos en varios aspectos. Se revisan las propiedades de cada señalfisiológica en términos de su practicidad y potencial. Se propone un método paraadaptar un clasificador a nuevos usuarios, estimando parámetros fisiológicosbasales. Luego se presentan dos métodos originales paramejorar las tasas de reconocimiento. El primero es un método supervisado basadoen mapas auto-organizativos (sSOM). Este método permite representar los espacios de características fisiológicas ymodelos emocionales, para analizar las relaciones en los datos. El otro estabasado en máquinas de aprendizaje extremo (ELM),una novedosa familia de redes neuronales artificiales que tiene gran poder degeneralización y puede entrenarse con pocos datos. Los métodos fueron evaluados y comparados con los del estadodel arte, en corpus realistas y de acceso libre. Los resultados obtenidos muestran avances en relación al estado del arte para el problema. Elmétodo de adaptación permite, a partir de pocos segundos,mejorar las tasas de reconocimiento en tiempo real, aproximando los resultados delreconocimiento que se podría hacer con posterioridad, sobre los registros completos. Utilizando una única señal de actividad cardiovascular, en particularla variabilidad del ritmo cardíaco (HRV), se lograron avances prometedores, con diferencias significativasen relación a los resultados obtenidos por los métodos del estado del arte. LasELM obtuvieron excelentes resultados y con bajo costo computacional, por lo queserían útiles para aplicaciones móviles. El sSOMlogra resultados similares, con la ventaja de proveer a la vez una herramientapara representar y analizar los espacios complejos de la fisiología y lasemociones, en una forma compacta.Fil: Bugnon, Leandro Ariel. Universidad Nacional del Litoral; Argentin

Photoplethysmography in noninvasive cardiovascular assessment

The electro-optic technique of measuring the cardiovascular pulse wave known as photoplethysmography (PPG) is clinically utilised for noninvasive characterisation of physiological components by dynamic monitoring of tissue optical absorption. There has been a resurgence of interest in this technique in recent years, driven by the demand for a low cost, compact, simple and portable technology for primary care and community-based clinical settings, and the advancement of computer-based pulse wave analysis techniques. PPG signal provides a means of determining cardiovascular properties during the cardiac cycle and changes with ageing and disease. This thesis focuses on the photoplethysmographic signal for cardiovascular assessment. The contour of the PPG pulse wave is influenced by vascular ageing. Contour analysis of the PPG pulse wave provides a rapid means of assessing vascular tone and arterial stiffness. In this thesis, the parameters extracted from the PPG pulse wave are examined in young adults. The results indicate that the contour parameters of the PPG pulse wave could provide a simple and noninvasive means to study the characteristic change relating to arterial stiffness. The pulsatile component of the PPG signal is due to the pumping action of the heart, and thus could reveal the circulation changes of a specific vascular bed. Heart rate variability (HRV) represents one of the most promising quantitative markers of cardiovascular control. Calculation of HRV from the peripheral pulse wave using PPG, called pulse rate variability (PRV), is investigated. The current work has confirmed that the PPG signal could provide basic information about heart rate (HR) and its variability, and highly suggests a good alternative to understanding dynamics pertaining to the autonomic nervous system (ANS) without the use of an electrocardiogram (ECG) device. Hence, PPG measurement has the potential to be readily accepted in ambulatory cardiac monitoring due to its simplicity and comfort. Noncontact PPG (NPPG) is introduced to overcome the current limitations of contact PPG. As a contactless device, NPPG is especially attractive for physiological monitoring in ambulatory units, NICUs, or trauma centres, where attaching electrodes is either inconvenient or unfeasible. In this research, a prototype for noncontact reflection PPG (NRPPG) with a vertical cavity surface emitting laser (VCSEL) as a light source and a high-speed PiN photodiode as a photodetector is developed. The results from physiological experiments suggest that NRPPG is reliable to extract clinically useful information about cardiac condition and function. In summary, recent evidence demonstrates that PPG as a simple noninvasive measurement offers a fruitful avenue for noninvasive cardiovascular monitoring. Key words: Photoplethysmography (PPG), Cardiovascular assessment, Pulse wave contour analysis, Arterial stiffness, Heart rate (HR), Heart rate variability (HRV), Pulse rate variability (PRV), Autonomic nervous system (ANS), Electrocardiogram (ECG).EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Contribuição para a compreensão da microcirculação periférica e da sua regulação através dos componentes oscilatórios do fluxo medido por laser doppler

Orientação: Maria Julia Buján, Luís Monteiro Rodrigues; co-orientação: Hugo FerreiraA microcirculação refere-se ao conjunto dos vasos sanguíneos com calibre inferior a 150 μm responsáveis pelo transporte de oxigénio e nutrientes para as células e de produtos do metabolismo para os sistemas de eliminação. O fluxo sanguíneo microcirculatório é regulado de forma complexa, por mecanismos intrínsecos e extrínsecos aos próprios tecidos. Qualquer disfunção que ocorra numa rede microvascular poderá comprometer a viabilidade tecidular A pele tem sido explorada, desde há vários anos, como um modelo potencialmente representativo dos fenómenos de regulação normal e alterada do fluxo sanguíneo microcirculatório, em larga medida devido à facilidade de acesso à sua rede microvascular. O estudo da microcirculação cutânea tem sido progressivamente facilitado pelo desenvolvimento de diversas tecnologias não invasivas, como é o caso da fluxometria por laser Doppler (LDF) e da gasimetria transcutânea, entre as mais utilizadas. Por último, é cada vez mais frequente realizar manobras de provocação que visam alterar as condições iniciais de perfusão e induzir respostas compensatórias, aumentando a sensibilidade da análise. Contudo, muitas destas tecnologias registam fenómenos oscilatórios de natureza complexa e de difícil interpretação, o que limita o acesso a esta informação in vivo. A exploração do sinal de LDF, em particular dos seus componentes oscilatórios, torna-se essencial para o estudo da regulação da microcirculação em condições de perfusão normal e alterada, pelo que orientámos o presente estudo no sentido de aprofundar o nosso conhecimento sobre estes temas através da questão “qual a contribuição dos componentes oscilatórios do sinal de LDF para a regulação da função microcirculatória“ ? Para responder a esta pegunta estabelecemos os seguintes objetivos: (i) desenvolver metodologias que permitam obter parâmetros funcionais microcirculatórios in vivo em indivíduos saudáveis de diferentes idades e caracterizar eventuais alterações relacionadas com o envelhecimento; (ii) encontrar as melhores ferramentas de análise fina do sinal de LDF; (iii) desenvolver um modelo animal que permita testar os intrumentos até aqui desenvolvidos, olhando mais aprofundadamente, se possível, para os fenómenos em causa; viii Para o primeiro objetivo foram estudados dois grupos de indivíduos saudáveis – um grupo de 35 indivíduos jovens, com idades compreendidas entre os 18 e os 30 anos (22,1 ± 3,7), e um grupo de 30 indivíduos saudáveis, mais velhos, com idades compreendidas entre os 40 e os 65 anos (50,8 ± 7,6). Em ambos os grupos foram registados sinais de LDF, de pressão transcutânea de oxigénio (tcpO2) e de perda transepidérmica de água (PTEA) durante a realização de três protocolos experimentais – elevação passiva da perna, oclusão supra-sistólica ao nível do tornozelo e respiração de oxigénio a 100%. Para o segundo objetivo foram aplicadas três ferramentas de análise – a transformada de wavelet (WT), a análise de flutuação retificada (DFA) e a análise de entropia à multiescala (MSE). Para o terceiro objetivo foi utilizado um grupo de 16 murganhos C57BL/6 com idades entre as 8 e as 27 semanas, tendo sido submetidos à respiração de oxigénio a 100% enquanto sedados e outro grupo de 9 murganhos de 16 semanas aos quais foi induzida isquémia unilateral do membro posterior, submetidos ao protocolo de respiração de oxigénio a 100%, antes e depois desta indução. Os resultados obtidos pelos objetivos, permitiram chegar às seguintes conclusões: (i) o protocolo de elevação passiva da perna provoca uma resposta vascular semelhante à encontrada no protocolo de oclusão supra-sistólica, podendo ser utilizado como alternativa a este; ambos induzem respostas hiperémicas compensatórias comparáveis. A oclusão permitiu revelar uma relação inversa entre a amplitude do sinal de LDF e a amplitude da PTEA, o mais importante indicador da função de “barreira” epidérmica; (ii) o protocolo de respiração de oxigénio a 100% é o mais fácil de aplicar no humano. O padrão de resposta envolve na maioria dos casos diminuição da perfusão / vasoconstrição embora o aumento da perfusão / vasodilatação também tenha sido observado. No entanto, a análise dos sinais de LDF não permitiu encontrar diferenças estatisticamente significativas nas respostas vasculares entre indivíduos de idades diferentes. Já a gasimetria transcutânea permitiu encontrar menores níveis de tcpO2 em indivíduos mais velhos, refletindo uma redução da capacidade de extração de oxigénio. A relação inversa entre o sinal de LDF e a PTEA foi aqui consistentemente registada. (iii) as análises de WA e de MSE foram as que demonstraram maior interesse na comparação das alterações das propriedades dos sinais de LDF entre as diferentes ix fases de cada protocolo e na comparação de indivíduos de diferentes idades. O protocolo de elevação passiva da perna foi o único que permitiu encontrar diferenças nas respostas vasculares, avaliadas por LDF, entre indivíduos de diferentes idades – indivíduos mais velhos apresentam um maior nível de perfusão basal, explicada por uma maior atividade miogénica, com menor nível de entropia, e respondem à manobra de elevação com uma maior atividade miogénica e simpática juntamente com uma menor atividade endotelial independente de monóxido de azoto (NO) face aos indivíduos mais jovens; (iv) O modelo animal revelou: a. Como no humano, um padrão de resposta vascular à respiração de oxigénio a 100% semelhante, com diminuição da perfusão / vasoconstrição e aumento da perfusão / vasodilatação; b. Neste modelo, após a indução da isquémia do membro posterior, o membro controlo respondeu consistentemente com diminuição de perfusão enquanto que o membro isquémico respondeu com aumento de perfusão; c. Ainda como nos humanos, conseguimos identificar, no murganho, seis bandas espetrais no sinal de LDF, compatíveis com as seguintes atividades: cardíaca (5,3- 4,6 Hz), respiratória (3,8-3,2 Hz), miogénica (0,17-0,059 Hz), simpática (0,052-0,020 Hz), endotelial NO-dependente (0,017-0,0094 Hz), e endotelial NO-independente (0,0084-0,0042 Hz); d. Tratar-se de um modelo adequado para o estudo da fisiologia e da patofisiologia circulatórias; (v) A análise de wavelet é aquela que melhor permite compreender a contribuição dos diferentes determinantes que competem para a regulação da microcirculação durante a resposta às diferentes condições de perfusão experimentalmente desenvolvidas. A resposta de diminuição da perfusão / vasoconstrição relacionada com a hiperóxia parece dever-se à redução de ambas as componentes endoteliais, em ambos os modelos.Microcirculation refers to blood vessels with a diameter lesser than 150 μm, responsible for the transport of oxygen and nutrients and removal of waste products to elimination systems to and from cells. The tissue’s microcirculatory blood flow regulation is complex and involves intrinsic and extrinsic mechanisms. Any dysfunction occurring in a given microvascular network might compromise the tissue viability and function. For many years, the skin has been explored as a model to study normal and abnormal microcirculatory blood, potentially representing flow regulation phenomena. The ease of access to its microvascular network is a major favorable argument. Also, the study of microcirculation has been progressively facilitated by the development of several non-invasive technologies, such as the laser Doppler flowmetry (LDF) and the transcutaneous gasimetry, some of the most used. Finally, provocation maneuvers aiming to change the initial perfusion conditions through which reflex responses are evoked are also frequently used, and contribute to increased analysis sensitivity. However, these technologies record oscillatory phenomena complex in nature and difficult to interpret, which limits the in vivo utility of this information. To explore these oscillatory components of the LDF signal, in particular, it becomes essential to look further into normal and altered perfusion regulation conditions. Thus, the present study is designed to deepen our knowledge on these matters through the question “how do LDF oscillatory components contribute to the regulation of microcirculatory function”? To answer this question the following objectives were established: (i) to develop methodologies that will allow to obtain functional microcirculatory parameters in vivo in healthy patients of different ages, and to characterise eventual changes related to ageing; (ii) to find the best calculation tools to refine the analysis of LDF signal; (iii) to develop an animal model that allows us to test the best instruments developed, looking deeper, if possible, into the related phenomena; For the first objective, two groups of healthy volunteers were studied – one group of 35 healthy volunteers, aged between 18 and 30 years old (22.1 ± 3.7), and one other group of xi 30 volunteers, also healthy but older, aged between 40 and 65 years old (50.8 ± 7.6). In both groups the LDF, transcutaneous oxygen pressure (tcpO2) and transepidermal water loss (TEWL) signals were recorded following the application of three experimental protocols – passive leg raising, suprasystolic occlusion at ankle level, and 100% oxygen breathing. For the second objective, three analytical tools were applied – the wavelet transform (WT), the detrended fluctuation analysis (DFA), and the multiscale entropy analysis (MSE). For the third objective, one group of 16 C57BL/6 mice was used, aged between 8 and 27 weeks old, submitted to a 100% oxygen breathing while anesthetized, and another group of 9 mice, 16 weeks old, submitted to an unilateral hindlimb ischemia, breathing 100% oxygen before and after procedure. Results obtained by objectives, allowed the following conclusions : (i) the passive leg raising protocol provokes a similar vascular response to the one obtained with the suprasystolic occlusion protocol, and might be used as an alternative; they both induce comparable compensatory hyperemic responses. Occlusion revealed a reciprocal relationship between LDF and TEWL, the most important indicator of epidermal “barrier” function; (ii) the 100% oxygen breathing protocol is the easiest to apply in humans. The response pattern consists in perfusion reduction/vasoconstriction in the majority of the cases, although perfusion increase / vasodilation has also been observed. Nevertheless, LDF signal analysis did not reveal statistically significant differences between vascular responses of patients with different ages. Transcutaneous gasimetry have shown lower tcpO2 in older patients, reflecting a reduction in the capacity of extracting oxygen. The reciprocal relationship between LDF and PTEA was clearly confirmed; (iii) The WT and MSE analysis demonstrated higher value for comparing LDF changes in the different phases of each protocol, and for comparing patients of different ages; the passive leg raising found differences in the vascular responses, evaluated with LDF, between patients of different ages. Older patients exhibited a higher baseline perfusion level, explained by a larger myogenic activity, with a lower entropy level, and responded to the raising maneuver with higher myogenic and sympathetic activities, together with a lower NO independent endothelial activity, when compared with younger patients; xii (iv) The animal model revealed: a. a pattern of vascular response to the 100% oxygen breathing protocol similar to humans, involving both perfusion reduction / vasoconstriction and perfusion increase / vasodilation; b. In this model, after the hindlimb ischemia procedure, the control limb responded consistently with a perfusion reduction, while the ischemic limb responded with an increase in perfusion; c. Again, as in human, we were able to identify, in the LDF signal, six spectral bands compatible with the following activities - cardiac (5.3-4.6 Hz), respiratory (3.8-3.2 Hz), myogenic (0.17-0,059 Hz), sympathetic (0,052-0.020 Hz), endothelial NOdependent (0.017-0.0094 Hz) and endothelial NO-independent (0.0084-0.0042 Hz); d. To be a suitable model to study circulatory physiology and pathophysiology. (v) The Wavelet analysis is the best to understand how different determinants contributions compete to regulate microcirculation as part of the response to the perfusion changes experimentally developed. In both models, the flow reduction/ vasoconstrictor response related to hyperoxia seems to result from the activity decrease of all endothelial components

Analysis and characterization of photo-plethysmographic signal

Qualitative assessment of the overall clinical status of the subject and characterization of complex cardiovascular dynamics from digital blood volume pulsations measured noninvasively using a photo-plethysmographic device is addressed. A novel concept is employed to detect the dominant nonsinusoidal periodicity embedded in the data series and to extract the associated periodic component. The detection and the extraction of periodic component is performed with moving window to accommodate the variations of the physiological oscillations. The covariance matrix formed by the gradually varying pattern is used as a simple measure of qualitative assessment. Further, the characterization of the underlying system in the light of nonlinear dynamical analysis is also presented. The stable subjects are shown to behave as a low-dimensional system whereas the diseased subjects exhibit comparatively high dimensional activi