Relationship between design and control of artificial heart for protection of the right/left balance.

Right/left matching in the total artificial heart (TAH) is essential to prevent fatal volume displacement into the pulmonary circuit. Measurements were made with three different sized Rostock pneumatic artificial ventricles incorporated in the Donovan mock circulatory system together with the heart driver AKT 86. First for each ventricle we determined the dependence of the maximum effective stroke volume on the systolic driving pressure and the afterload. The right ventricle (RV) is about 10% more effective than the left ventricle (LV). Control of the TAH permits different or equal frequencies for the RV and LV. For control with equal frequencies and full-to-empty regimen of one ventricle (RV-Master or LV-Master) the ratio of designed stroke volumes between RV and LV is important. This follows from the smaller efficiency of the LV and the left-to-left shunt. Otherwise a control mode with different heart rates must be used.

Optokinetic nystagmus in homonymous hemianopia due to a strictly occipital lesion.

Optokinetic nystagmus (OKN) was tested in 15 patients with unilateral strictly occipital brain lesions and complete homonymous hemianopia and compared with findings in a group of normal controls. Quantitative analysis of the results in the patients revealed a bilateral disorder of OKN. When the stimulus was moved in the direction opposite to the hemianopic field, there was a significant decrease in optokinetic gain, and the amplitude of nystagmus decreased. There was no correlation between OKN and size of the residual macular field.

[The status of prazosin in therapy of chronic heart failure]. / Der Stellenwert des Prazosins bei der Therapie der chronischen Herzinsuffizienz.

Cardiac dysfunction and neurohumoral dysregulation show that the administration of vasodilators is reasonable in a cardiac insufficiency which is therapy-refractory against glycosides and saluretics. The alpha 1-blocker prazosin is a potent substance. On the basis of haemodynamic investigations of 55 patients the acute effects are demonstrated. Depending upon the degree of the cardiac insufficiency and the sympathetic dysregulation--measured at the behaviour of the resistance--the acute effects are convincing in more than 60% of the patients. For the long-term course patients with unequivocal initial improvement are suitable. This group can undergo a satisfactory therapy for a longer time by means of a carefully increased dosage, by corrections of the application of saluretics and by short interruptions of therapy and by the change of the dilator, respectively, or by an additional administration of another vasodilator. In the total spectre of the vasodilators which are administered in cardiac insufficiency prazosin occupies one of the first places.

[Noninvasive monitoring of pneumatically driven blood pumps based on measurements of air volume flow in the drive hose]. / Nichtinvasive Uberwachung pneumatisch angetriebener Blutpumpen auf der Grundlage von Luftvolumenstrommessungen im Antriebsschlauch.

A computer-assisted measuring system for the noninvasive control of pneumatically driven blood pumps in the artificial total heart replacement and in assist-systems is described. Air volume current measurements with heat wire anemometer in the driving tube underlie as principle. The technique takes into consideration losses of valves, depending upon driving parameters and central circulatory parameters. The dependences established base on measurements at the circulation model. The methods demonstrated allow to qualitatively characterize the signals of the air volume current in the driving tube and approximatively to determine central circulatory parameters on the basis of comparative measurements at the circulation model. Animal-experimental experiences confirm the necessary application of such systems for the measurement of the cardiac output and for the control of the pumping function of pneumatically driven blood pumps. Analyses at the circulation model let expect a measuring error for the volume of output smaller than 20%. By increased measuring exactness of the heat wire anemometer this error can be diminished. For final evidence concerning the measuring exactness animal-experimental investigations and comparisons with reference techniques are provided.

[Catheter problems in the use of ventricular cardiovascular assist systems]. / Zur Kanülenproblematik bei der Applikation von ventrikulären Herz-Kreislauf-Assistsystemen.

The prerequisite for efficient assist-ventricles and impulses in the pulsatile pumping function are sufficiently dimensioned afflux and flowing off connections. In systematic investigations on the hydraulic circulation model the cannulas from an internal parameter of 12 mm with a total length of the connection distance to the inflow and outflow valve, respectively, at the bypass ventricle of 30 cm proved sufficient for performing a volume of output of 5-6 l/min in clinic-relevant filling pressures in a hypodynamic circulatory situation. Connection cannulas for the heart-lung machine used in routine work are not sufficient in periodic filling and ejection processes in the pulsatile pumping function for an effective decompression and effective increase of the cardiac output. In case of an ECG-triggered mode of action of the ventricular assist-system an increase of frequency up to 130/min in after that incomplete filling of the assist-ventricle does not remarkably restrict the effectiveness of the assist-system.

[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.

[Pressure measurements of pneumatically driven artificial ventricles]. / Druckmessungen an pneumatisch betriebenen künstlichen Ventrikeln.

In the mock circulation are investigated methods for pressure measurement developed especially for the application on artificial ventricles. They require the in-vivo-confirmation in the long-term experiment. An exact analysis of the pressure curves gives information about the absolute measuring values and also about the function of the pump itself, such as about the points of reaching the final positions of the pump membrane. Via a control related to this in the "full stroke" mode with ejection of the complete stroke volume, when the stand-still times of the membrane are minimized, in addition to this the atrial pressures and the cardiac output can be determined. Eventual non-linearities in the lower pressure region (less than or equal to 0.5 kPa) are not essential in the measurement of the ventricular pressure with amplitudes of 20-25 kPa on the left side and are not investigated in detail.

[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.

[Behavior of serum alkaline during pregnancy. II. Pathological pregnancy]. / Zum Verhalten der alkalischen Phosphatase im Serum während der Gravidität. II. Pathologische Schwangerschaft

832 estimations of heat stable alkaline phosphatase (HSAP) and of heat alkaline phosphatase (HLAP) were carried out simultaneously in late pregnant women at 25th to the 42nd weeks of pregnancy. 147 of them delivered children with normal birth-weight. All these women suffered from pre-eclampsia, hypertension or any kind of superimposed pre-eclampsia. 110 other pregnant women with or without symptoms of pre-eclampsia gave birth to small for dates babies. In addition, the values of these patients were compared with 372 estimations of the same enzymes carried out in 120 patients with normal pregnancy and outcome of normal weighted children. The site of the values of every group showed no typical correlation to the course and outcome of their pregnancy. Regarding four special criterions it was possible to give a good prediction by serial determinations for the weight of the newborn in 80 per cent of the cases. A correlation between the urinary excretion of total oestrogens as well as HLAP and the values of HSAP was to be found only in some groups of patients.

[Behavior of alkaline phosphatase in serum during pregnancy. I. Normal pregnancy]. / Zum Verhalten der alkalischen Phosphatase im Serum während der Gravität. I. Normale Schwangerschaft

On 120 patients, during normal pregnancy, from the 17th to the 42nd week of pregnancy, 372 heat labile alkaline phosphatase estimations were carried out by means of the 4-nitrophenol method. In addition to that, after incubation of sera at 65 degrees C for 30 minutes, the activity of the heat stable placental isoenzyme was checked. With progressing pregnancy, the heat stable fraction rises significantly and the heat labile fraction of total alkaline phosphatase increases slightly. There is a correlation between the readings of the two fractions. In 169 cases, the total urinary oestrogen output correlates also with the heat stable alkaline phosphatase.