Medical & biological engineering & computing
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Med Biol Eng Comput · Nov 1992
Theoretical analysis of the relationship between the ratio of ventricular systolic elastance to diastolic stiffness and stroke volume.
The maintenance of adequate blood circulation requires a sufficient ventricular contractility; in addition, to eject blood, the ventricles must first receive a sufficient volume, requiring a low diastolic stiffness. A simplified cardiovascular model was used to derive formulae for stroke volume (SV) as a function of atrial pressure and the ratio of ventricular end-systolic elastance to end-diastolic stiffness. A more complex cardiovascular model was used to assess the ability of the expressions to predict stroke volume under various steady-state conditions. ⋯ When the right atrial pressure was not fixed increases in GR with fixed GL reduced the right atrial pressure with little change in SV. Similarly, varying GL with fixed GR produced little change in SV. The ratios highlight the importance of diastole to cardiac function.
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Med Biol Eng Comput · Sep 1991
Evaluation of a new reflectance pulse oximeter for clinical applications.
The design of a noninvasive reflectance pulse oximeter that uses the same principle of transmittance pulse oximeter and analyses the oxygen saturation of arterial blood was described. Four sets of red and infra-red LEDs were used as light sources. ⋯ From 22 samples, a good correlation coefficient (0.98) with a standard deviation of 1.42 was obtained in the range between 73 and 100 per cent between the arterial oxygen saturation measured with the present instrument and that with the Co-Oximeter. The result strongly suggests the usefulness of this oximeter in monitoring patients with hypoxaemia.
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Med Biol Eng Comput · Jul 1991
Static dynamometer for the measurement of multidirectional forces exerted by the thumb.
The functioning of a static dynamometer designed to measure simultaneous forces exerted by the thumb in the vertical and horizontal axes is described. The analysis of the output signals by a desktop computer program provides information regarding the forces generated in eight directions covering a plane transverse to the thumb by 45 degree increments. ⋯ Dynamometric data indicate that strength varies with direction and that higher torques are obtained in directions that bring the thumb towards the palm, i.e. flexion, adduction, combined flexion-adduction and extension-adduction. Patterns of muscle activity vary according to the direction evaluated suggesting that strength depends on the number of activated muscles as well as the relative force contribution of each muscle.