Medical engineering & physics
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Computed tomography (CT) has been employed to determine non-invasively the distribution of subchondral bone density in joints and to evaluate their dominant loading pattern. The objective of this study was to investigate the relationship between subchondral bone adaptation, joint incongruity and loading, in order to determine to what extent the loading conditions and/or geometric configuration can be inferred from the distribution of subchondral density. Finite element models of joints with various degrees of incongruity were designed and a current remodeling theory implemented using the node-based approach. ⋯ However, other combinations of incongruity and loading produced similar subchondral density patterns. Both the geometric joint configuration and the loading conditions influence the distribution of subchondral density in such a way that one of these factors must be known a priori to estimate the other. Since subchondral density can be assessed by CT and joint geometry by magnetic resonance imaging, the dominant loading pattern of joints may be potentially derived in the living using these non-invasive imaging methods.
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Comparative Study
Monitoring of heart and respiratory rates by photoplethysmography using a digital filtering technique.
An apparatus for simultaneously monitoring heart and respiratory rates was developed using photoplethysmography (PPG) and digital filters, and compared with conventional methods. The PPG signal, which includes both heart and respiratory components, was measured at the earlobe with an original transmission mode photoplethysmographic device. A digital filtering technique was used to distinguish heart and respiratory signals from the PPG signal. ⋯ To obtain higher heart and respiratory rates, exercise was performed on an electrical bicycle ergometer. Heart and respiratory rates calculated by the new method compare to those obtained from ECG and the transthoracic impedance plethysmogram. The maximum error of heart and respiratory rates was 10 beats/min and 7 breaths/min, respectively.
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Comparative Study
Comparative testing of pulsatile impeller total heart and sarns nonpulsatile roller as biventricular assist device in pigs.
A pulsatile impeller total heart was developed, which consists of two impeller pumps and a d.c. motor. As the motor changes its rotating speed periodically, both pumps eject the blood flow simultaneously. To evaluate its blood compatibility, the device and sarns roller pumps were compared in two series of acute biventricular assist experiments in four and three pigs, respectively. ⋯ Blood sampling was drawn preoperatively, at the beginning of the pumping and every 2 h postoperatively. Red blood cells (RBC), white blood cells (WBC), platelets (PLT), hematocrit (HCT), hemoglobin (HB), free hemoglobin (FHB) and lactate dehydrogenase (LDH) were measured. The results demonstrated that there was no significant blood damage caused by impeller total heart and the clinically used roller, and that the pulsatile impeller total heart is suitable for chronic animal experiments.
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The impeller blood pump with its simplicity has many advantages compared with the diaphragm pump, but the nonpulsatile property has limited its applications. To make the impeller pump pulsatile, many investigations have been made in vain because of resulting haemolysis. The author has succeeded in producing a pulsatile blood flow with a centrifugal pump, by means of the streamlined design of the impeller. ⋯ Two pumps are located on both sides of and driven by a d.c. motor. As the motor changes its rotating speed periodically, the left and right pumps eject the blood simultaneously, and the volume equilibrium of both pumps is achieved naturally. Acute biventricular assist experiments in pig confirmed that the device caused no blood damage.