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Biomedical subjects

S Kono

Publications and source records attributed to S Kono.

369 records · Page 21Linked to original sources
PubMedDate not supplied

Results of chronic animal experiments with a new version of a magnetically suspended centrifugal pump.

We have developed a magnetically suspended centrifugal pump (MSCP) for long-term ventricular support. This study reports results of chronic animal experiments using a new version of the MSCP. Three sheep weighing 50-70 kg were used in this study. A left heart assist system was established with cannulas into the descending aorta and the left ventricular apex. In two sheep the MSCP was positioned outside the body and in one sheep implanted on the chest wall. The pumping flow was estimated by the motor current and motor speed. The temperature of the pump and the muscle near the pump was recorded for 10 days after operation. The duration of continuous pumping was 60, 140, and 230 days+ (ongoing), respectively. The cause of termination was infection associated with thrombus formation in the first, and failure of magnetic suspension in the second sheep. No thrombus or embolus was observed after sacrifice of the second sheep. The third sheep has been going well despite skin necrosis around the pump pocket. The estimation of pumping flow was reliable even at 140 days. Temperature of the pump surface was 42 degrees C immediately after the operation and gradually reduced to 41 degrees C. The MSCP is a reliable pump for long-term circulatory assist.

Animals↗
PubMedDate not supplied

Hemodynamics on abrupt stoppage of centrifugal pumps during left ventricular assist.

A magnetically suspended centrifugal pump (MSCP), developed for long-term ventricular assist, is reliable and durable because it has no shaft or seal. However, with nonvalve pumps such as a MSCP, regurgitation occurs when they accidentally stop without cannula clamping. We investigated the hemodynamics during temporary stoppage of a MSCP being used as a left ventricular assist system (LVAS), comparing two inflow cannulation sites. In four sheep (weight, 35-45 kg), microspheres were injected into the left main coronary artery to induce heart failure. An outflow cannula was sutured onto the descending aorta, and two inflow cannulae were inserted into the left atrium and the left ventricle. The MSCP was stopped with both the left ventricular cannula and left atrial cannula clamped, and the hemodynamics and P-V loops were recorded. Each cannula was then unclamped in order, and similar parameters were recorded. LVEDP increased at unclamping of the left ventricular cannula (ULVC), and rose further at unclamping of the left atrial cannula (ULAC). Aortic pressure did not change at ULVC, but decreased at ULAC. The effective systemic flow that subtracted the regurgitant flow through the MSCP from left ventricular output was half at ULVC and almost 0 at ULAC. When stopping centrifugal pumps without circuit clamping, hemodynamic deterioration is less at ULVC than at ULAC. This finding suggests that left ventricular inflow cannulation is recommended to allow more time in emergency situations.

Animals↗
PubMedDate not supplied

Five year prospective study on blood pressure and maximal oxygen uptake.

1. The relationship between physical fitness (maximal oxygen uptake VO2max) and incidence of hypertension was investigated through a prospective study for a total of 16,525 human-years of observation. 2. This study involved 3305 Japanese males whose blood pressure (BP) was normal when they received their first physical examination before the age of 50. They were monitored from 1983 to 1988. The BP of 425 subjects was diagnosed as hypertension in the fifth year. 3. Fitness levels were divided into quintiles according to VO2max levels, and were compared with the changes of BP and relative risk of hypertension after adjustment for age, initial percentage of body fat (PFAT), initial BP, alcohol consumption, cigarette smoking status and familial history of hypertension. The increase in BP of subjects in the least fit group was higher than in any other group. Relative risk was calculated using a multiple logistic regression and was 1.9 x higher in the least fit group compared with the fittest group. 4. The subjects were classified into three groups: the improved VO2max group, the deteriorated VO2max group and the unchanged VO2max group. The increase in BP of the improved VO2max group was significantly lower than the other two groups after adjustment for changes in PFAT, age, initial PFAT, initial BP, fitness level, alcohol consumption, cigarette smoking status and familial history of hypertension. 5. It is concluded that low VO2max level is related to higher incidence of hypertension. An improved VO2max would therefore be able to prevent hypertension.

Adult↗
PubMedDate not supplied

A retrospective analysis of 88 patients with pancreaticogastrostomy after pancreaticoduodenectomy.

BACKGROUND/AIMS: Recently, pancreaticogastrostomy after pancreaticoduodenectomy has been reintroduced as a useful procedure with a low incidence of pancreatic leakage. We decided to retrospectively analyze the early postoperative and late follow-up complications in a large number of patients who had undergone our improved pancreaticogastrostomy. METHODOLOGY: Between August 1993 and November 1998, we performed pancreaticogastrostomy following pancreaticoduodenectomy in 88 consecutive patients including pylorus preservation in 14. Our pancreaticogastrostomy used a two-layer implantation method using a pancreatic duct stent with an anterior gastrotomy. RESULTS: The morbidity and mortality rates were 5.7% and 0%, respectively. There were no cases of pancreatic leakage and no postoperative complications directly related to the pancreaticogastrostomy. As for gastric emptying, the average time until resumption feeding was 12 days, with no significant difference between pancreaticogastrostomy and pylorus-preserving pancreaticogastrostomy. As to late follow-up complications, diabetes developed postoperatively in 6.5% (4/62) patients, and of 14 patients who were shown by magnetic resonance cholangiopancreatography, 5 (35.7%) developed pancreatic ductal dilatation after surgery. CONCLUSIONS: These results from a relatively large group conclusively prove the safety of pancreaticogastrostomy and indicate that the follow-up quality of life is good under the circumstances.

Anastomosis, Surgical↗
PubMedDate not supplied

Tinea pedis in members of the Japanese Self-defence Forces: relationships of its prevalence and its severity with length of military service and width of interdigital spaces.

We examined the relationship between prevalence and severity of tinea pedis and the length of service and the width of the spaces between the toes in 74 members of the Japanese Self-Defence Forces (SDF) undergoing special training. The subjects were divided according to the width of these spaces into: group I, wide; group II, fairly wide; and group III, closed. The severity of tinea pedis was determined by its duration and the extent of the lesions in the 49 subjects who had tinea pedis. The combined prevalence of tinea pedis and tinea unguium was 66%. There was a tendency for the prevalence to be higher in subjects who had served for 10 years or more in the SDF than in those with fewer than 10 years of service. Classified by the disposition of their toes, 10 subjects fell into group I, 34 into group II, and 30 into group III. The prevalence of 90% (27/30) in group III was significantly higher than in the other groups. A significant positive correlation was seen between length of SDF service and severity. Subjects with both a long service record and closed interdigital spaces showed both a high prevalence and marked severity.

Adult↗
PubMedDate not supplied

Control of the pressure flow relationship with a magnetically suspended centrifugal pump in a chronic animal experiment.

A magnetically suspended centrifugal pump (MSCP) has been developed for long-term ventricular support. Effective torque to blood of the MSCP is exactly proportional to a motor current because of no friction inside the MSCP. The authors have devised new driving modes using these characteristics and applied it to a chronic animal experiment. Three driving modes were compared: 1) a constant rotational speed (N), 2) a constant motor current (I), and 3) a controlled motor current (CI). In two of nine sheep, the MSCPs were operated by the N and in seven by the I mode. The motor current and the rotational speed were always monitored. The CI mode was studied by altering the resistance of the vessels. In the I mode, the rotational speed varied depending upon the pressure head, and the slope of the pressure-flow (P-Q) relationship was steeper than that of the N mode, so that the pump flow was stabilized. In the CI mode, in which the motor current increased to compensate for the decrease in pump flow as the rotational speed increased, the P-Q slope was effectively controlled when the resistance was changed. The MSCP was able to control the P-Q slope without monitor of the pump flow. Various driving modes could be selected according to changes in resistance.

Animals↗
PubMedDate not supplied

In vivo and in vitro evaluation of the pulsatile mode of a magnetically suspended centrifugal pump.

The authors have been developing a magnetically suspended centrifugal pump (MSCP). They have devised a pulsatile mode for the MSCP, which was generated by altering rotational speed. This article describes in vitro and in vivo studies with the pulsatile mode of the MSCP. Hemolysis tests were performed in two identical circuits to compare the nonpulsatile (NP) mode and the pulsatile (P) mode. In vivo studies were performed in sheep. First, biventricular assisted circulation was instituted in the left heart with the MSCP and in the right heart with the Biopump. The native heart was induced to ventricular fibrillation. Second, a left ventricular assisted circulation was instituted as the native heart was beating. An inflow cannula was inserted into the left atrium in one sheep and into the left ventricle in the other. The normalized indices of hemolysis of the NP and P groups were 0.0025 +/- 0.0018 g/100 L, and 0.0032 +/- 0.0024 g/100 L (N = 4, not significant). During ventricular fibrillation in the P mode, the pulse pressure was 14 mmHg (the rotational speed: 1,500 to 2,600 rpm). In a beating heart, at atrial withdrawal, the pulse pressure increased from 10 to 24 mmHg (2,100 +/- 500 rpm), while at ventricular withdrawal, it decreased from 17 to 40 mmHg (2,000 +/- 500 rpm) on P mode. The MSCP in pulsatile mode did not increase hemolysis. At ventricular withdrawal, it was easier to produce a pulsation than at atrial withdrawal. The pulsatile mode of the MSCP is applicable to a left ventricular assist system.

Animals↗