Schuster's scattering theory was applied to a blood model and a theoretical formula of the blood optical attenuation change for unit blood thickness change was obtained. Several factors affecting the optical attenuation of blood were investigated in vitro and the blood optical attenuation change for unit blood thickness change was measured in vitro for 600-1, 300nm. With an increase of the size of the transmittance window, and with an increase of the thickness of the blood, the blood optical attenuation for unit blood thickness change decreased to a certain limit. In the condition of this limit, it was able to select a suitable value for the scattering constant for each hematocrit so that the theoretical blood optical attenuance agreed with the measured value. As hematocrit increased, in low hematocrit range, the scattering constant increased almost proportionally to hematocrit, and after certain hematocrit value, the scattering constant decreased. These theory and experimental observations can be used to refine and improve the technology of pulse oximetry.

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Lasers have been utilized extensively for therapeutics and diagnostics in mdicine, like laser-induced hyperthermia and non-invasive measurement of oxygenation state by near-infrared lasers. Temperature rises of laser-irradiated tissues need to be predicted for prevention of thermal injury, where precise temperature control is necessary or higher energy input is desirable. In order to provide the basic data for safety, this report presents the profiles of the absorbed and transmitted energy calculated by the Monte Carlo method, and by use of the resuls the temporal thermal behaviors of an irradiated body are analysed by solving the bioheat transfer equation. The body is assumed to be a sphere of 30mm diameter, having uniform thermophysical and optical properties of living tissues. The results show the effects of the scattering and absorption coefficients on the absorbed energy density and transmitted energy flux. The resultant temperature variations are found to be mainly dependent on the absorption coefficient and the heat transfer to the environment.

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The purpose of the present study was to identify the cardiovascular response to lower body negative pressure in severely disabled patients during prolonged recumbency and to represent their deterioration using the discriminant function. Fifteen disabled patients and ten healthy volunteers entered the investigation. After 5min of supine rest for a control period, each subject underwent the LBNP test of -20mmHg during 5min. The disabled patients were categorized into two groups: H₁ group whose members maintained thin blood pressure during LBNP in the range of normal subjects and H₂ group who showed greater decrease than -2RMS error of the normal value. Both disabled groups demonstrated significantly higher heart rate (HR) in addition to both less stroke volume (SV) and cardiac output (CO) comparing with the normal subjects. Exposure to LBNP in the disabled patients produced reduction in SV and CO over the limit value resulting in decreased blood pressure. The compensatory increase in HR did not observed obviously in the H₁ but also the HR in the H₂ reduced lower than the velue at rest. Endocrine response in the disabled groups was insufficient comparing with the normal subjects. Deteriorated cardiovacular response in the disabled patients may result from both decreased total blood volume and dysfunction of baroreceptor-mediated reflex due to prolonged bedrest. Description of cardiovascular function by the discriminant function is useful for evaluating degree of the deconditioning and effects of the functional training.

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We had already reported that eye tracking movement characteristics are influenced by the attention with which a subject tries to look at a moving target. The target brightness feedback (TBF) method, which feeds back to a subject by using the brightness of a moving target whether he is tracking it precisely or not, was designed in order to raise his attention level. In the TBF condition, it was suggested to the subject that the target would be brighter if he fixated the target, and he was instructed to track the target so that it became as bright as possible. The target was moved sinusoidally (1Hz, ±10deg). Four saccadic and three smooth pursuit parameters were defined. Among them, the phase of smooth pursuit interested us. Although it was behind the target movement originally, it was delayed more by the TBF and the SD decreased simultaneously. This means that the phase delays and becomes stable in accordance with the rise of the attention level. The change ratio of each parameter was calculated by using the differences of both average and SD of the parameter between the non-feedback and the TBF condition by a specific algorithm. The result shows that the characteristics regularly change with the attention level independent of the subjects. We suggest that the attention level change, especially between one data-acquisition and the other acquisitions for each subject, can be estimated by the algorithm. However, the algorithm does not make it possible to estimate the attention fluctuation with time during tracking. So the average of the amplitude of smooth pursuit obtained from the 10 subjects (20 trials) was shown as a function of target period. It decreased gradually with the target period. This is an anticipated result. We suggest that the amplitude of smooth pursuit can express the attention level variation in time.

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A variety of computer models had been proposed so as to simulate the electric phenomena in a human heart. All these models are composed of numerous “units”. Since the excitation is assumed to propagate step by step to the adjacent units in a specific time, it is difficult to deal with anisotropic and inhomogeneous propagation. In order to overcome these difficulty, we introduce here a new model in which a heart is divided into tetrahedral elements. Characteristics of the myocardium such as directional dependence of the conduction velocity and the action potential waveform are assigned to each vertexes of the tetrahedra as a few parameters. Being interpolated, these parameters are specified all over the heart. In this way, the anisotropic and inhomogeneous propagation as well as the spatial dependence of the action potential waveform can be taken into account. It is also possible to evaluate the influences of the anisotropy in electric conductivity on the EMF source.

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