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Biomedical subjects

W O'Bannon

Publications and source records attributed to W O'Bannon.

At least 19 recordsLinked to original sources
PubMed1983

Behavior of endothelial cells cultured on Silastic and Dacron velour under flow conditions in vitro: implications for prelining vascular grafts with cells.

Tissue-cultured bovine aortic endothelial cells were subjected to flow in an in vitro circulatory loop designed to simulate the flow and pressure conditions in the aorta. The cells were cultured under stationary conditions on tubes of fibronectin-coated Silastic or of Dacron velour. The tubes were then added to the flow loop, which circulated complete tissue culture medium in a pulsatile mode. Light microscopy and cell counts showed that the cells not only remained adherent for up to 2 weeks under flow conditions, but also underwent hypertrophy and proliferation in response to the flow regimen.

Animals↗
PubMed1982

In vitro evaluation of U.S. and U.S.S.R. artificial hearts.

This report summarizes the results of the in vitro evaluation of Soviet and American artificial hearts. The devices were tested at the All-Union Institute of Transplantation and Artificial Organs, Moscow, U.S.S.R., and Baylor College of Medicine, Houston, Texas, U.S.A. These studies were designed to standardize procedures to allow comparison of artificial ventricles of different designs. Also, these studies might provide a means for evaluation of other characteristics such as hemolysis, durability, and reliability. Static and dynamic tests were performed, varying preload, afterload, rate, and systolic and diastolic time intervals. All designs demonstrated comparable function curves with capability of taking over the pressure and volume work of the natural heart.

Blood Flow Velocity↗
PubMed1982

Performance of tissue cultured endothelial cells in a mock circulatory loop.

Tissue cultured bovine aortic endothelial cells were subjected to flow in an in vitro circulatory loop which was designed to simulate the flow and pressure conditions in the aorta. The cells were cultured to confluence under stationary conditions on a tube consisting of microfabric backed with polyurethane. The tube with the cultured cells was then added to the flow loop which circulated complete tissue culture medium in a pulsatile mode. Light microscopy, and scanning and transmission electron microscopy showed that the cells not only remained adherent for 2 week periods under flow conditions, but also underwent hypertrophy and proliferation in response to the flow regimen.

Animals↗
PubMed1980

A second generation portable life support system.

Recognizing the need to transport critically ill patients to a specialized facility, we have designed a profound life support system. PLSS addresses the demand for mobility by placing all support systems under a patient cart. It addresses the demand for reliable power supply by providing a redundancy in sources. Ease of operation and further reliability are attained by automation. This system incorporates existing life support technology. Improvement is gained by combining the merits of several systems as well as by providing for portability. A synergistic effect which is obtained by combining IABP and VABP makes this portable device a unique and powerful clinical tool.

Critical Care↗
PubMed1977

Recent experience with the Baylor left ventricular bypass pump.

The current Baylor left ventricular bypass pump is a pneumatically actuated diaphragm pump lined with segmented polyurethane. It is a swirl design in which blood moves in a circular motion within the pump. It has tilting disc inflow and outflow valves and the stroke volume is 60 ml. It is intended for periods of use up to fourteen days. Eighteen devices have been implanted in normal calves. The mean duration of pump operation was eleven days. The pump-canula junctions and regions of the valve seats have been sites of thrombus formation and are being redesigned to eliminate areas of flow separation and stasis.

Animals↗
PubMed1976

Design and evaluation of a percutaneous transthoracic cannula.

This investigation was designed to develop a satisfactory PTC for conveying large bore cannulae as required for current use with the artificial heart and left heart assist device. A total of 50 PTCs of varying designs and 6 controls were implanted in the dorsum of canines and goats. Observations with 6 initial designs indicated that necessary requirements in the design of a PTC, include adequate fixation and the use of dacron or nylon velour as the skin interfacing material. Best results were obtained utilizing a PTC having a polycarbonate extra-cutaneous flange, a nylon velour covered polycarbonate subcutaneous skirt, and an extended threaded central conduit to also allow fixation intrathoracicly behind the 2 ribs traversed by the device. Eight such PTCs have been implanted and without complications, have exhibited good tissue ingrowth and have had negative bacterial cultures for periods averaging 6 mos. The use of a PTC of this design should be considered in conjunction with mechanical hearts or left heart assist devices where large bore conduits must cross the chest wall and function on a chronic basis without allowing the ingress of virulent organisms.

Animals↗
PubMed1976

Automatic control of the artificial heart.

An automatic control system has been developed to balance and control the output of an artificial heart. The system consisted of 2 linked negative feedback loops. The left ventricle was controlled by a Servo-Stroke Optimizer, which insured complete filling and full stroke operation of the left pump with each beat and changed the beat rate in accord with changes in aortic pressure. The right ventricle was controlled by a Servo-Variable Systolic Duration unit, which changed the stroke of the right ventricle to maintain the left atrial pressure within a preset band. In the initial animal studies, control pressures (aortic and left atrial pressure) were obtained from implanted transducers. More recently, a method has been devised whereby the control pressures were obtained from specific points on the left air line pressure wave, obviating the need for implanted transducers. The control system has been evaluated in a mock circulatory loop and in 9 calves with implanted artificial hearts. The system has provided balance of the 2 implanted ventricles and changes in flow rate in response to changes in peripheral resistance. The need for an operator to make manual adjustment to the power units has been considerably reduced. Further studies are indicated to evaluate the function of the control system in animals performing moderate-to-maximal exercise. Furthermore, the ultimate benefits of full stroke operation vs fill limited mode operation remain to be delineated.

Animals↗
PubMed1976

A comparison of three ventricles used for left ventricular bypass in the calf.

Long-term synchronized left ventricular bypass has been performed in calves using pneumatically powered pumps having a smooth lining fabricated of segmented polyurethane. Three different pump designs have been employed: a) sac pump, b) longitudinal tethered sac pump, and c) transverse tethered sac pump. Sizeable thrombi occurred in the apex of the sac and longitudinal tethered sac pumps. In the transverse tethered sac pumps, a considerably smaller thrombus was seen only at the flexion point on the inlet side of the pump. Thrombi occurred in areas of low flow velocity and were not prevented by anticoagulation or surface coating techniques. This study indicates the importance of ventricle design in the development of thrombus free pumps and suggests modifications to the present pumps to reduce or eliminate thrombus formation.

Animals↗
PubMed1974

Complete left ventricular bypass with a paracorporeal pump: design and evaluation.

A multidiscipline group was established at The Pennsylvania State University to design and evaluate mechanical circulatory assist devices and the artificial heart. The group has designed a left ventricular to aortic assist system which consists of a sac-type pump, a synchronization unit, a pneumatic power unit, and appropriate monitoring apparatus. The assist system has been evaluated for long-term circulatory assistance in a series of ten calves. The assist pump was placed in the paracorporeal position. The longest period of continuous pumping was over eight months. The last four calves have had synchronized assist pumping which has permitted prolonged ventricular decompression and assist pump flow rates as high as 10 L/min. Three of these four calves had no evidence of thromboemboli. Additional animal studies will be required before clinical use of such an assist pump system can be safely undertaken.

Animals↗