[Filling behavior of pneumatically driven artificial ventricles of the membrane type in vitro]. / Füllungsverhalten pneumatisch betriebener künstlicher Ventrikel vom Membrantyp in vitro.

The filling behaviour of pneumatically driven artificial hearts is an essential determinant of its pumping function. The artificial ventricles developed in Rostock were investigated by means of a hydraulic circulation model for analysis of the influence of different parameters on the filling time. The filling rate is decided by the flow resistance of the inlet valve. Additional resistances are given by the rigidity of the membrane and the flow resistances of the drive line and the drive.

[Pathophysiological investigations on the function of artificial hearts]. / Pathophysiologische Betrachtungen zur Funktion künstlicher Herzen.

The mode of action of artificial hearts is in a wide range variable and to be adapted to different conditions of the circulatory systems. The direct regulative function of the peripheral circulation is restricted by the rigid ability of artificial hearts bound to motor drive parameters. Their great dependence on pre- and afterload already in normal calves presumes a harmonized functional capacity of the right and left ventricle. As to the situation in potential recipients of artificial hearts with considerably disturbed macro- and microhaemodynamics there are problems for the choice of suitable conditions of motor drive, in order to favour a right-left balance and an adequate volume. The substitution of the natural regulators by suitable sensors and the regulation of the artificial hearts according to haemodynamic controls and pump parameters, respectively, is necessary to achieve a balanced adequate ventricular function. This complex is subject of an intensive research.

Assessment of mechanical properties and biocompatibility of Pellethane.

Pellethane CPR 2363-80A nonreinforced (PUR), non-reinforced and twice sterilized (PUR F2), reinforced with Dacron (Dm), Grisuten (DG) and glassfibre (PUG) and fabricated under different conditions have been examinated. Tests included uniaxial tension at 310 K, torsional movement from 293 to 319 K, X-ray structure, SEM, visual surface clotting, thrombocyte adhesion and degree of albumenisation. Typical in vitro results were: modulus of elasticity E [MPa] (PUR: 1.33, Dm: 4.22, DG: 1.86, PUG: 622.5), tensile strength delta B [MPa] (43.4, 12.5, 21.7, 24.9), elongation at break delta [%] (1122, 109, 660, 479), dynamic modulus of sliding G', G" [MPa] at 293 K (8.7, 0.4/ 15.9, 0.9/ 12.1, 1.3/ 17.1, 1.5), damping tan delta (0.13, 0.1, 0.16, 0.12), orientational degree at 5% elongation fx [%] (PUR: 0.5), low thrombogenicity and high degree of albumenisation. The results indicate a strong dependency of mechanical and biocompatibility properties on membrane and housing fabrication. The most effective combination is a thin PUR membrane and a PUG housing fabricated under special conditions.