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Biomedical subjects

Y Sohara

Publications and source records attributed to Y Sohara.

71 records · Page 4Linked to original sources
PubMed1980

Improved pulmonary venous anastomosis using a single left atrial cuff in one-stage bilateral lung autotransplantation.

A technical modification in pulmonary venous anastomosis is presented for one-stage bilateral lung autotransplantation in dogs. This method nullified or minimized both narrowing and loss of vascular distensibility due to scar formation at anastomotic line which inevitably resulted in functional defects after the operation. In this new procedure, bilateral pulmonary arteries were anastomosed using angioplastic techniques and both right and left pulmonary veins were sutured orthotopically as a single atrial cuff. Of 11 dogs which underwent one-stage bilateral lung replantation, 6 survived after operation. Sites of vascular anastomoses in the long-term survivors showed no narrowing due to scar formation at autopsy after hemodynamic examination. In these animals rapid and continuing infusion of 2000 to 3000 ml of blood or plasma explander was performed within 15 min through an intraatrial catheter. Various hemodynamic values were measured simultaneously. In the dog with bilateral lung transplants pulmonary arterial pressure showed linear increase with an increase in cardiac output when compared with control animal studies. It could be interpreted from these results that some changes occurred in the mechanism of pulmonary circulation of the transplant.

Animals↗
PubMedDate not supplied

Pitfalls in the development of a rotary blood pump controller.

The controller presents a major obstacle in the development of the rotary blood pump as a left ventricular assist device (LVAD). Clinically, LVAD flow is a good indicator in the regulation of circulatory conditions and pump flow changes, depending on pump preload and afterload. Many investigators have tried estimating pump flow by referencing the motor current. There have been pitfalls in in vitro experimental settings, however. Using a test loop with a pneumatically driven LV chamber and a centrifugal pump as an LVAD, we monitored pump flow and pressure head to evaluate the pump performance curve (H-Q curve). Under pulsatile LV conditions, the H-Q curve was a loop that changed, depending on LV contractility. The pneumatically driven LV chamber cannot mimic the Starling phenomenon, so the developed LV pressure does not change according to the LV preload. Rotary pump flow estimation is the most effective control method. In pulsatile conditions, however, the H-Q curve is a loop that changes under various LV contractility conditions, complicating determination of linear equation for calculating flow. In addition, the LV chamber in the test loop cannot mimic native heart contractility as described by Starling's law. This finding can lead to a misanalysis of the H-Q curve under pulsatile conditions.

Cardiac Output↗
PubMedDate not supplied

Pulmonary microcirculation during pulsatile and non pulsatile perfusion.

During development of a rotary blood pump as an assist device, the efficacy of non pulsatile perfusion to the end organ has to be verified. However, there are few evaluations of two different perfusion mechanisms through the tissue microcirculation. In this study, the pulmonary microcirculation was analyzed by vital microscopic observation. Wistar rats weighing 400-500 g were anesthetized and ventilated by a respirator. After establishing right heart bypass from the right atrium to the pulmonary artery using a roller pump, the pulmonary microcirculation was observed during intravenous infusion of bovine albumin tagged with fluorescein isothiocyanate. The images were recorded on a videotape through an ultra-sensitive SIT TV camera. Initially, the pulmonary circulation was pulsatile, produced by the native heart, and the pulmonary capillary network was evenly perfused by the blood. After starting the pump, the flow became non pulsatile and the distribution of capillary perfusion was displaced to the short circuit connecting the pulmonary arterioles and venules. Flow distribution during non pulsatile perfusion was heterogeneous compared with pulsatile perfusion. This result suggests that non pulsatile flow may lead to the deterioration of function. Further investigation is necessary to evaluate the relationship between the microcirculation and organ function.

Animals↗