71 research outputs found

    A Systemic Review of Functional Near-Infrared Spectroscopy for Stroke: Current Application and Future Directions

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    Background: Survivors of stroke often experience significant disability and impaired quality of life. The recovery of motor or cognitive function requires long periods. Neuroimaging could measure changes in the brain and monitor recovery process in order to offer timely treatment and assess the effects of therapy. A non-invasive neuroimaging technique near-infrared spectroscopy (NIRS) with its ambulatory, portable, low-cost nature without fixation of subjects has attracted extensive attention.Methods: We conducted a comprehensive literature review in order to review the use of NIRS in stroke or post-stroke patients in July 2018. NCBI Pubmed database, EMBASE database, Cochrane Library and ScienceDirect database were searched.Results: Overall, we reviewed 66 papers. NIRS has a wide range of application, including in monitoring upper limb, lower limb recovery, motor learning, cortical function recovery, cerebral hemodynamic changes, cerebral oxygenation, as well as in therapeutic method, clinical researches, and evaluation of the risk for stroke.Conclusions: This study provides a preliminary evidence of the application of NIRS in stroke patients as a monitoring, therapeutic, and research tool. Further studies could give more emphasize on the combination of NIRS with other techniques and its utility in the prevention of stroke

    Advancing orthostatic hypotension diagnostics

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    This thesis investigated the diagnostics of orthostatic hypotension (OH). OH is defined as a sustained systolic/diastolic blood pressure (BP) drop larger than 20/10 mmHg within 3 minutes after standing up. OH is common among older adults aged above 65 years (6 – 31%) and geriatric outpatients (22-56%), sometimes accompanied by orthostatic intolerance (dizziness, light-headedness and blurry vision) and associated with poor clinical outcome (cardiovascular diseases, impaired cognitive performance and mortality). Current OH diagnostics is limited due to 1) contradictory evidence on the association between the OH definition and physical functioning and falls; 2) the uncertainty of the clinical value of continuous BP measurements, which may in contrast to intermittent sphygmomanometer measurements reflect the challenge posed to compensation systems and brain exposure to low perfusion pressures; and 3) the lack of assessment of systems compensating for orthostatic BP drops such as baroreflex sensitivity (i.e., heart rate increase in response to a BP drop to stabilize BP), peripheral vasoconstriction (i.e., narrowing of peripheral artery diameter in response to a BP drop to increase peripheral resistance and stabilize BP) and cerebral autoregulation (i.e., dilation of cerebral arterioles in response to a BP drop to keep cerebral blood flow constant). In conclusion, the currently used OH definition was found to be clinically valuable as patients diagnosed according to this definition are at increased risk of impaired physical functioning and falls. BP drop rate and BP recovery derived from continuous BP measurements were found to have added clinical value by their association with clinical outcome and may after confirmation of the results in further studies have to be incorporated in a new OH definition for continuous orthostatic BP measurements to better identify individuals with clinical consequences due to OH. Parameters expressing baroreflex sensitivity, cerebral oxygenation and cerebral autoregulation were by their sensitivity, test-retest reliability and validity in younger and older adults demonstrated to be potentially valuable, supporting further study on the clinical value of these parameters

    Analysis of the Relationship between Sacral Skin Blood Flow and Transcutaneous Oxygenation in Response to Causative Factors of Pressure Ulcers in Healthy Subjects

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    Pressure ulcers significantly contribute to the diminished quality of life and substantial disability in people with spinal cord injury (SCI). A broad consensus among clinicians and researchers has been reached that the best approach to reducing this burden is to implement an effective preventive treatment that would greatly reduce the incidence. The preventative intervention should eliminate/diminish causative factors and pathways involved with pressure ulcer development. The objective of this thesis is to explore the relationship between sacral skin blood flow and transcutaneous oxygenation in response to causative factors of pressure ulcers (i.e. thermal stress, mechanical stress, and sympathetic modulations) in five neurologically intact subjects.Two tests were performed to analyze the relationship between sacral skin blood flow and transcutaneous oxygenation. In test 1, skin blood flow and transcutaneous oxygenation were measured while subjects underwent orthostatic stimulation. Results from test 1 showed that both the level of heat used and the location of testing effects how skin blood flow and transcutaneous oxygenation respond to orthostatic stimulation. In test 2, skin blood flow and transcutaneous oxygenation were measured while external pressure was applied. Results from test 2 showed that a significant increase in peak skin blood flow and TcPO2 (p<0.05) occurred on average 588 and 298 seconds, respectively, following removal of occluding pressure when the skin is heated to 44 degrees C; however, at 37 degrees C, skin blood flow and transcutaneous oxygenation showed a significant peak increase (p<0.05) following removal of occluding pressure at 28 and 404 seconds, respectively

    Cerebral autoregulation assessed by near-infrared spectroscopy:validation using transcranial Doppler in patients with controlled hypertension, cognitive impairment and controls

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    PURPOSE: Cerebral autoregulation (CA) aims to attenuate the effects of blood pressure variation on cerebral blood flow. This study assessed the criterion validity of CA derived from near-infrared spectroscopy (NIRS) as an alternative for Transcranial Doppler (TCD). METHODS: Measurements of continuous blood pressure (BP), oxygenated hemoglobin (O(2)Hb) using NIRS and cerebral blood flow velocity (CBFV) using TCD (gold standard) were performed in 82 controls, 27 patients with hypertension and 94 cognitively impaired patients during supine rest (all individuals) and repeated sit to stand transitions (cognitively impaired patients). The BP-CBFV and BP-O(2)Hb transfer function phase shifts (TF(φ)) were computed as CA measures. Spearman correlations (ρ) and Bland Altman limits of agreement (BAloa) between NIRS- and TCD-derived CA measures were computed. BAloa separation < 50° was considered a high absolute agreement. RESULTS: NIRS- and TCD-derived CA estimates were significantly correlated during supine rest (ρ = 0.22–0.30, N = 111–120) and repeated sit-to-stand transitions (ρ = 0.46–0.61, N = 19–32). BAloa separation ranged between 87° and 112° (supine rest) and 65°–77° (repeated sit to stand transitions). CONCLUSION: Criterion validity of NIRS-derived CA measures allows for comparison between groups but was insufficient for clinical application in individuals. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00421-021-04681-w

    Cardio-postural Interactions and Muscle-pump Baroreflex Are Severely Impacted by 60-day Bedrest Immobilization

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    To understand fundamental mechanisms associated with post-flight orthostatic intolerance we investigated the interaction between the cardiovascular and postural functions before and after 60 days of head down bedrest (HDBR). Twenty healthy young males (35.0&thinsp;±&thinsp;1.7 years) were subjected to 60-day HDBR at 6˚ to simulate spaceflight-induced fluid shifts. A supine-to-stand (STS) test was conducted to evaluate cardio-postural control before and after (R) HDBR while an assessment of cardiovascular function was performed during HDBR. Beat-to-beat heart period, systolic blood pressure, and electromyography impulses were derived for wavelet transform coherence and causality analyses of the cardio-postural control and used to assess changes in the muscle-pump baroreflex. During quiet stand of the STS test, compared to baseline, heart rate was 50% higher on the day of exit from bedrest (R0) and 20% higher eight days later (R8). There was a 50% increase in deoxygenated hemoglobin on R0 and R8. Leg muscle activity reduced, and postural sway increased after HDBR. Causality of the muscle-pump baroreflex was reduced on R0 (0.73&thinsp;±&thinsp;0.2) compared to baseline (0.87&thinsp;±&thinsp;0.2) with complete recovery by R8. The muscle-pump baroreflex also had decreased gain and fraction time active following HDBR. Overall, our data show a significantly impaired muscle-pump baroreflex following bedrest

    A consensus guide to using functional near-infrared spectroscopy in posture and gait research

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    BACKGROUND: Functional near-infrared spectroscopy (fNIRS) is increasingly used in the field of posture and gait to investigate patterns of cortical brain activation while people move freely. fNIRS methods, analysis and reporting of data vary greatly across studies which in turn can limit the replication of research, interpretation of findings and comparison across works. RESEARCH QUESTION AND METHODS: Considering these issues, we propose a set of practical recommendations for the conduct and reporting of fNIRS studies in posture and gait, acknowledging specific challenges related to clinical groups with posture and gait disorders. RESULTS: Our paper is organized around three main sections: 1) hardware set up and study protocols, 2) artefact removal and data processing and, 3) outcome measures, validity and reliability; it is supplemented with a detailed checklist. SIGNIFICANCE: This paper was written by a core group of members of the International Society for Posture and Gait Research and posture and gait researchers, all experienced in fNIRS research, with the intent of assisting the research community to lead innovative and impactful fNIRS studies in the field of posture and gait, whilst ensuring standardization of research

    Reflex syncope : an integrative physiological approach

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    Síncope, a forma mais comum de perda temporária de consciência é responsável por até 5% das idas aos serviços de emergência e até 3% dos internamentos hospitalares. É um problema médico frequente, com múltiplos gatilhos, incapacitante, potencialmente perigoso e desafiante em termos diagnósticos e terapêuticos. Assim, é necessária uma anamnese detalhada para primeiro estabelecer a natureza da perda de consciência, mas, após o diagnóstico, as medidas terapêuticas existentes são pouco eficazes. Embora a fisiopatologia da síncope vasovagal ainda não tenha sido completamente esclarecida, alguns mecanismos subjacentes foram já desvendados. Em última análise, a síncope depende de uma falha transitória na perfusão cerebral pelo que qualquer factor que afecte a circulação sanguínea cerebral pode determinar a ocorrência de síncope. Assim, o objectivo do presente estudo é caracterizar o impacto hemodinâmico e autonómico nos mecanismos subjacentes à síncope reflexa, para melhorar o diagnóstico, o prognóstico e a qualidade de vida dos doentes e dos seus cuidadores. Para isso, desenhámos e implementámos novas ferramentas matemáticas e computacionais que permitem uma avaliação autonómica e hemodinâmica integrada, de forma a aprofundar a compreensão do seu envolvimento nos mecanismos de síncope reflexa. Além disso, refinando a precisão do diagnóstico, a sensibilidade e a especificidade do teste de mesa de inclinação (“tilt test”), estabelecemos uma ferramenta preditiva do episódio iminente de síncope. Isso permitiu-nos estabelecer alternativas de tratamento eficazes e personalizadas para os doentes refractários às opções convencionais, sob a forma de um programa de treino de ortostatismo (“tilt training”), contribuindo para o aumento da sua qualidade de vida e para a redução dos custos directos e indirectos da sua assistência médica. Assim, num estudo verdadeiramente multidisciplinar envolvendo doentes com síncope reflexa refractária à terapêutica, conseguimos demonstrar uma assincronia funcional das respostas reflexas autonómicas e hemodinâmicas, expressas por um desajuste temporal entre o débito cardíaco e as adaptações de resistência total periférica, uma resposta baroreflexa atrasada e um desequilíbrio incremental do tónus autonómico que, em conjunto, poderão resultar de uma disfunção do sistema nervoso autónomo que se traduz por uma reserva simpática diminuída. Igualmente, desenhámos, testámos e implementámos uma plataforma computacional e respectivo software associado - a plataforma FisioSinal –incluindo novas formas, mais dinâmicas, de avaliação integrada autonómica e hemodinâmica, que levaram ao desenvolvimento de algoritmos preditivos para a estratificação de doentes com síncope. Além disso, na aplicação dessas ferramentas, comprovámos a eficácia de um tratamento não invasivo, não disruptivo e integrado, focado na neuromodulação das variáveis autonómicas e cardiovasculares envolvidas nos mecanismos de síncope. Esta terapêutica complementar levou a um aumento substancial da qualidade de vida dos doentes e à abolição dos eventos sincopais na grande maioria dos doentes envolvidos. Em conclusão, o nosso trabalho contribuiu para preencher a lacuna entre a melhor informação científica disponível e sua aplicação na prática clínica, sustentando-se nos três pilares da medicina translacional: investigação básica, clínica e comunidade.Syncope, the most common form of transient loss of consciousness, accounts for up to 5% of emergency room visits and up to 3% of hospital admissions. It is a frequent medical problem with multiple triggers, potentially dangerous, incapacitating, and challenging to diagnose. Therefore, a detailed clinical history is needed first to establish the nature of the loss of consciousness. However, after diagnosis, the therapeutic measures available are still very poor. Although the exact pathophysiology of vasovagal syncope remains to be clarified, some underlying mechanisms have been unveiled, dependent not only on the cause of syncope but also on age and various other factors that affect clinical presentation. Ultimately, syncope depends on a failure of the circulation to perfuse the brain, so any factor affecting blood circulation may determine syncope occurrence. Thus, the purpose of the present study is to understand the impact of the hemodynamic and autonomic functions on reflex syncope mechanisms to improve patients diagnose, prognosis and general quality of life. Bearing that in mind, we designed and implemented new mathematical and computational tools for autonomic and hemodynamic evaluation, in order to deepen the understanding of their involvement in reflex syncope mechanisms. Furthermore, by refining the diagnostic accuracy, sensitivity and specificity of the head-up tilt-table test, we established a predictive tool for the impending syncopal episode. This allowed us to establish effective and personalised treatment alternatives to patient’s refractory to conventional options, contributing to their increase in the quality of life and a reduction of health care and associated costs. In accordance, in a truly multidisciplinary study involving reflex syncope patients, we were able to show an elemental functional asynchrony of hemodynamic and autonomic reflex responses, expressed through a temporal mismatch between cardiac output and total peripheral resistance adaptations, a deferred baroreflex response and an unbalanced, but incremental, autonomic tone, all contributing to autonomic dysfunction, translated into a decreased sympathetic reserve. Through the design, testing and implementation of a computational platform and the associated software - FisioSinal platform -, we developed novel and dynamic ways of autonomic and hemodynamic evaluation, whose data lead to the development of predictive algorithms for syncope patients’risk stratification. Furthermore, through the application of these tools, we showed the effectiveness of a non-invasive, non-disruptive and integrated treatment, focusing on neuromodulation of the autonomic and cardiovascular variables involved in the syncope mechanisms, leading to a substantial increase of quality of life and the abolishment of syncopal events in a vast majority of the enrolled patients. In conclusion, our work contributed to fill the gap between the best available scientific information and its application in the clinical practice by tackling the three pillars of translational medicine: bench-side, bedside and community
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