Search PubMed⌕ Search

Biomedical subjects

R Kiraly

Publications and source records attributed to R Kiraly.

41 records · Page 3Linked to original sources
PubMedDate not supplied

Study of heat dissipation to the lung from a thermal ventricular assist system.

The thermally powered left ventricular assist system (LVAS) requires that heat be dissipated to surrounding lung tissue and blood. This acute study was conducted in three anesthetized calves (weighing 84.3 +/- 14.3 kg) to evaluate the mechanisms involved in the dissipation of heat to the lung tissue. The heaters were placed in contact with the left lung surface and skeletal muscle tissue. Compared to the muscle tissue, heat flux to the lung was approximately three times higher for the same surface temperatures. For a constant heat flux, lung interface temperature tended to vary inversely with the cardiac output and ventilatory flow. This preliminary study demonstrated that the level of heat generated by the thermal LVAS can be effectively dissipated to the lung, with the convection mechanisms of airflow and blood flow playing a major role.

Animals↗
PubMedDate not supplied

Initial in vivo tests of an electrohydraulic actuated total artificial heart.

The authors are involved in developing a total artificial heart (TAH) for permanent human use. This device was designed to fit human anatomy, and it has housings made of carbon fiber-epoxy composite and titanium. Tissue valves and protein coating of blood contacting surfaces minimize the need for anticoagulants. A continuously reciprocating electrohydraulic actuator is packaged between two alternately ejecting and passively filling ventricles. The control system varies the pump rate to maintain average left ventricular filling at 90%. This TAH in vivo successively progressed through 1, 5, 9, and 45 day implants in calves of 84, 94, 82, and 82 kg preoperative body weights. The operating modes include automatic and fixed rate. The chronic and acute effects of varying the right pump displaced stroke volume indicated the need for it to be limited to 85% of that of the left for stable hemodynamics at maximum flow. The pump exhibited afterload insensitive and preload sensitive performance. Pump output ranged from 4.0-9.5 L/min at left atrial pressures of 7-16 mmHg at pump rates of 80-160 beats/min in these four experiments. These data suggest that this device will meet clinical hemodynamic requirements; it has the potential for total implantable cardiac replacement.

Animals↗
PubMedDate not supplied

The coiled envelope-a disposable insert for coil dialysis.

The coiled envelope, a disposable pre-sterilized insert for coil dialysis, and its associated hardware were developed. In vitro and in vivo characterizations of the dialyzer were carried out and clinical dialyses performed. Clinical studies show the efficacy of the device and indicate advantages in its design. The dialyzer can be assembled in less than 5 minutes. The blood fluid path materials are replaceable in the coiled envelope kidney and can be certified sterile and pyrogen-free for each dialysis. This is a distinct advantage over the reuse of commercial dialyzers which can not be certified after their initial use. The disposable insert could be made available for patient use at a cost about one-half that of present commercial dialyzers.

Animals↗
PubMedDate not supplied

Flow visualization in an artificial heart using diffuse and planar laser lighting.

The purpose of the study was to characterize flow properties within a clinical pusher plate type artificial heart. Dual camera video tape and synchronized still photographs were used to study flow patterns. Diffused light and a planar laser source provided illumination. The laser light was turned into a plane of light with a thickness varying from 0.1 to 10 mm, and magnesium oxide and Amberlite particles were used as tracers. Qualitative and quantitative analyses were performed by the examination and digitization of flow patterns. Inflow, outflow, pneumatic drive and after-load pressure, diaphragm motion, cardiac output, and heart rate were measured and recorded. An electrical circuit was developed to synchronize pump diaphragm motion with captured images of flow trajectories. Trajectories were then digitized, and velocities, turbulence, and shear stresses were calculated. As the result of these experiments, disturbed, recirculating, and stagnation zones were identified and global and local turbulence values were determined. Simultaneous turbulence, stasis, recirculation, and laminar flow patterns were observed during most phases of the pumping cycle. Velocities obtained varied from 2 cm/sec to 145 cm/sec; total local shear stresses of 12 to 897 dynes/cm2 were seen.

Blood Flow Velocity↗