Biomedical subjects

U Losert

Publications and source records attributed to U Losert.

95 records · Page 6Linked to original sources

PubMedDate not supplied

Laryngeal pacemaker: activity of the posterior cricoarytenoid muscle (PCM) and the diaphragm during respiration in sheep.

Electromyograms (EMG) of the PCM and the diaphragm were evaluated in 6 sedated female sheep. Corresponding pneumatograms were recorded simultaneously by means of thermocontrolled respiration flowmeter. Evidence was obtained on considerable intra- and inter-individual differences in the duration of respiratory cycles as well as PCM- and diaphragmatic activity. Most of the evaluated respiratory periods showed either a phase coincidence between the PCM and the diaphragm, or a leading edge of about 40-80 ms of the posticus muscle. Due to this minimal phase shift, the diaphragmatic myogram seems to be a valuable trigger for an external PCM stimulation unit in bilateral recurrent nerve palsy.

Animals↗

PubMedDate not supplied

Influence of centrifugal blood pumps on the elasticity of erythrocytes.

The influence of centrifugal blood pumps on the elasticity of erythrocytes was tested in an in vitro set-up. Fresh bovine blood was pumped by vaneless and impeller blood pumps with low and high hemolytic potential (1L priming volume, flow 5 L/min versus 150 mmHg, pumping time 6 hours). The elasticity of the red blood cells was measured by laser diffraction. Starting with an elasticity of 238 +/- 39, the overall change during 6 hours was 12 +/- 38 compared to a change of the control value of -13 +/- -58. Even a pump with very high hemolytic potential (Hemolysis index 21.9) did not cause relevant changes of elasticity. It is concluded that 1) elasticity is not a useful parameter to use in the evaluation of centrifugal pumps, and 2) the mechanical trauma caused by centrifugal pumps produces no relevant permanent alteration of the elastic properties of red blood cells, at least under in-vitro conditions.

Animals↗

PubMedDate not supplied

Platelet function after total artificial heart replacement: clinical application and experiment.

Clinical application of artificial blood pumps for mechanical circulatory support has been hampered by thromboembolic events. The underlying mechanisms are complicated and may differ from patient to patient. Because the calf is commonly used for artificial heart studies, the object was to determine the value of data gained in an animal model. To this end, the average of 10 calf experiments was compared with three clinical applications of an orthotopically implanted total artificial heart in patients with terminal heart failure. Platelet reactivity was investigated in vitro by collagen-induced whole blood aggregometry, radioimmunoassay methods, and scanning electron microscopy over a 10-day period. An analogous periodicity of platelet function was found in human and animal recipients. Improvement of platelet function preceded that of platelet counts in the early postoperative phase. Exaggerated responses to aggregative agents were observed at days 3 and 7. On the basis of our data, we believe that we can comment about the prospective course of the function and number of human platelets, which may contribute to the identification of critical phases of such treatment, during total artificial heart replacement.

Adult↗

PubMedDate not supplied

Artificial heart driven by an automatic driving system.

Thrombi formation within artificial ventricles is caused by the effects of biomaterials, stagnation areas, and major turbulences. During systolic and diastolic cycles, stagnation area increase in hearts that are properly designed. Stagnation areas may also occur in properly designed artificial hearts that are not working with a maximum stroke volume. The ellipsoid heart avoids stagnation areas and major turbulences because all the inside surfaces have an adequate washout with blood. The optimum washout of these surfaces is obtained by driving the heart with a constant maximum stroke volume. The cardiac output is regulated according to Starling's law by adjusting the frequency according to the venous return.

Animals↗

PubMedDate not supplied

The Windkesselventricle with guiding balloon as a new approach for assisted circulation.

A simple method was developed to aid the patient with low cardiac output syndrome following cardiac surgery. The concept was shown to be feasible in electric circulatory analog studies and verified in 20 dog experiments. A Dacron graft (end-to-side) through the right second intercostal space connects the ascending aorta to the subcutaneously implanted, ellipsoidal-shaped artifical ventricle. A spherical polyurethane balloon is positioned in the aorta distal to the Dacron graft via the femoral artery. The ventricle and balloon are pneumatically driven synchronously with the ECG. In natural systole the balloon is inflated, occluding the aorta, and the artificial ventricle sucks the entire stroke volume. In natural diastole the balloon deflates and the artificial ventricle ejects the blood into the peripheral arteries. With this system it is possible to maintain a normal systemic pressure and have high hemodynamic efficiency. The left ventricular systolic pressure is 85 percent unloaded. The systolic wave is turned 180 degrees to the natural. After treatment, the device can be removed without thoracotomy.

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