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We present an unobtrusive cuff-less sphygmomanometer based on contact-type and optical pulse sensors for continuous and minimally invasive monitoring of blood pressure (BP). We developed a cuff-less sphygmomanometer that utilizes the pulse arrival time (PAT) to estimate continuous BP. To assess its accuracy, we recruited 10 healthy subjects in whom we carried out BP studies using the cuff-less sphygmomanometer compared with a standard cuff-type device in a stationary sitting patient. Preliminary results showed that the mean difference (MD) of estimated systolic blood pressure and diastolic blood pressure were 0.96 ± 9.6 (mean ± SD) mmHg and 1.14 ± 7.5 mmHg, respectively, compared to the control. The corresponding correlation between the estimated BP values and controls were 0.78 for systolic blood pressure (p < 0.01) and 0.69 for diastolic blood pressure (p < 0.01); thus, there were significant correlations. These results suggest that the developed cuff-less sphygmomanometer has the potential for continuous BP monitoring. Finally, we conducted a preliminary study of simultaneous monitoring of cuff-less BP and near-infrared spectroscopy to evaluate the potential for assessment of autonomic nervous system functions during mental stress tasks.

Vascular cognitive impairment (VCI) plays an important role in dementia in elderly people, and refers to the contribution of vascular pathology to the entire spectrum of cognitive disorders, ranging from mild cognitive impairment to severe dementia, as well as the pathological spectrum, from ‘pure’ Alzheimer disease through degrees of vascular comorbidity to ‘pure’ vascular dementia. In the present study, we investigated the relationship between cognitive dysfunction and systemic metabolic disorders, by employing deep learning (DL). We studied 202 patients (73.4 ± 13.0 years), 94.6% of whom were undergoing treatment for lifestyle diseases, and 68.8% of whom had a history of cerebrovascular disorder. We evaluated cognitive dysfunction by performing a Mini Mental State Examination (MMSE). We performed general blood examination, including Complete Blood Count and Basic Metabolic Panel, and measured cerebral blood oxygenation in the prefrontal cortex (PFC) using time-resolved near infrared spectroscopy (TNIRS). We then used deep neural networks to assess the MMSE scores of the subjects based on the TNIRS parameters and the blood examination data, independently. Next, we compared predicted MMSE scores based on the TNIRS and the blood examination. There was a significant positive correlation between the TNIRS parameters and the blood examination data (r = 0.6, p < 0.01). These observations suggest that cognitive dysfunction in patients with VCI may be caused by combinations of systemic metabolic disorders such as energy and oxygen metabolisms and cerebral circulatory disturbance due to arteriosclerosis resulting from lifestyle-related diseases.

The incidence of stress-induced psychological and somatic diseases has been increasing rapidly, and it is important to clarify the neurophysiological mechanisms of stress response in order to establish effective stress management methods. We previously reported that the prefrontal cortex (PFC) plays an important role in stress response. In the present study, we employed near-infrared spectroscopy (NIRS) and electroencephalography (EEG) to investigate the characteristics of PFC activity during mental arithmetic tasks. A two-channel NIRS device was used to measure hemoglobin (Hb) concentration changes in the bilateral PFC during a mental arithmetic task (2 min) in normal adults. Simultaneously, EEG was used to also measure bilateral PFC activity during the same task. We evaluated concentration changes of oxy-Hb induced by the task while analyzing α wave changes using power spectrum analysis. It was observed that oxy-Hb in the bilateral PFC increased significantly during the task (p < 0.05), while α wave power in the PFC decreased significantly (p < 0.01). The present results indicate that mental stress tasks caused the activation of the bilateral PFC. Simultaneous measurements of NIRS and EEG are useful for evaluating the neurophysiological mechanism of stress responses in the brain.

Near infrared spectroscopy (NIRS) has been applied to measurements of cerebral blood oxygenation (CBO) in normal subjects and patients with various brain disorders including cerebrovascular diseases. However, it is not known whether NIRS allow us to measure CBO correctly in patients with abnormal cortices where optical characteristics such as optical pathlength (OP) may differ from those in normal cortex. In the present study, employing a time-resolved NIRS (TNIRS), we compared baseline hemoglobin (Hb) concentrations and OPs between normal and abnormal cortices in chronic stroke patients. We studied five patients with chronic cerebral infarction (two males, three females, age 59.0 ± 24.2 years) who were admitted to the University Hospital of Fukushima Prefectural Medical University. Employing TNIRS (TRS-20, Hamamatsu Photonics), we measured baseline Hb concentrations and OPs (760, 800, 830 nm) at various positions on the head. We observed that deoxy-Hb concentrations were significantly lower on the affected side (p < 0.01), and the tissue oxygen saturation was significantly higher than that on the affected side (p < 0.01), suggesting that oxygen consumption was reduced on the affected side. In addition, the OPs (760, 800 nm) were significantly longer on the affected side (p < 0.05); these changes might be caused by a possible increase of cerebrospinal fluid layer associated with brain tissue degeneration by ischemia. The present results suggest that NIRS should be performed on patients with abnormal cerebral cortices, giving special consideration to the possible difference in optical characteristics between normal and abnormal brain tissues.

Muscle infarction after bypass graft occlusion for atherosclerotic occlusive disease in non-diabetic patients is uncommon. The diagnosis of minor muscle necrosis not requiring surgical debridement in the presence of an acute graft occlusion is often difficult to make. The incidence of this problem in non-diabetic patients with artheroscleotic disease as well as the utility of magnetic resonance imaging in the diagnosis of minor muscle necrosis are presented below.

The electrical recovery characteristics of relatively small air gaps between 0.3 and 9 mm were determined using a two-pulse method. The first pulse was used to over-volt the gap and initiate the arc current. The second pulse was used to determine the recovery voltage of the gap. A plot of the recovery voltage with time was obtained by varying the time delay of the second pulse relative to the arc extinction time of the first arc, in the time range form 50 mu s to 100 ms. It is found that the recovery characteristics are independent of the electrode materials (Cu, Al , St) and the arc current in the range from 40 to 200 A. It is also found that the shorter gaps and the rod plane gaps recover their dielectric strength faster than the longer gaps and the sphere gaps, respectively. >