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Biomedical subjects

A C Hansen

Publications and source records attributed to A C Hansen.

59 records · Page 4Linked to original sources
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In vivo long-term evaluation of the Utah electrohydraulic total artificial heart.

An electrohydraulic total artificial heart (EHTAH) has been developed and evaluated by long-term in vivo studies. The EHTAH is composed of blood pumps with an interatrial shunt (IAS), an energy converter, and electronics. The EHTAH with external electronics was implanted in four calves weighing from 81-90 kg. Two animals died on the 1st and 5th post operative days, the third animal survived for 32 days, and the fourth for 159 days. The IAS was free of thrombus at autopsy in all animals. The longest surviving animal increased in size from a pre operative weight of 81 kg to 134 kg on day 144. Cardiac output ranged from 9.3 to 10.5 L/min, whereas right and left atrial pressures increased with the calf's growth from 4-10 to 16-20 mmHg and from 8-14 to 18-22 mmHg, respectively. The animal favorably tolerated up to 3.4 km/hr of treadmill exercise, both hemodynamically and metabolically. The elevation of atrial pressures during treadmill exercise was significantly alleviated by employing an automatic control mode. It is concluded that the device has the potential to be a totally implantable system for permanent use.

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Verification testing of the bearings used in the electrohydraulic total artificial heart.

This article reports the verification testing performed on the ball bearings used in the electrohydraulic total artificial heart (EHTAH) device. The bearings were tested for 70 days under conditions intended to simulate those actually experienced by the bearings in the EHTAH device. Vibration analysis to predict the condition of the bearings, as well as diagnosis of the wear experienced by the bearings, was included in this study. Examination of the bearings using light microscopy indicated the presence of wear, and in some instances the contact surfaces had undergone temper coloring, a warning sign that hardness of the bearing may have been impaired, and that the bearing has experienced a temperature excursion. Temper coloring can be caused by too thick a coating of grease or by insufficient hydrodynamic film thickness. In this investigation, the vibration amplitudes at specific frequencies that correlated with the bearing components were monitored for change. From analysis of the vibration spectra, it was found that the change in amplitude did not predict the damage incurred by the bearings. The type of damage experienced by the bearings is difficult to predict using spectral analysis.

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