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Hiroshi Ohtake

Publications and source records attributed to Hiroshi Ohtake.

13 recordsLinked to original sources
PubMed2006

Switching fuzzy controller design based on switching Lyapunov function for a class of nonlinear systems.

This paper presents a switching fuzzy controller design for a class of nonlinear systems. A switching fuzzy model is employed to represent the dynamics of a nonlinear system. In our previous papers, we proposed the switching fuzzy model and a switching Lyapunov function and derived stability conditions for open-loop systems. In this paper, we design a switching fuzzy controller. We firstly show that switching fuzzy controller design conditions based on the switching Lyapunov function are given in terms of bilinear matrix inequalities, which is difficult to design the controller numerically. Then, we propose a new controller design approach utilizing an augmented system. By introducing the augmented system which consists of the switching fuzzy model and a stable linear system, the controller design conditions based on the switching Lyapunov function are given in terms of linear matrix inequalities (LMIs). Therefore, we can effectively design the switching fuzzy controller via LMI-based approach. A design example illustrates the utility of this approach. Moreover, we show that the approach proposed in this paper is available in the research area of piecewise linear control.

Algorithms↗
PubMed2006

Robotic replacement of the descending aorta in human cadaver.

Robot-assisted replacement of the thoracic aorta was performed in a human cadaver. Temporary shunt bypass was established by inserting a left axillary artery catheter and directing it through the aortic arch toward the right femoral artery through the abdominal aorta. The technique utilized the da Vinci surgical system inserted through the 4-cm supramammary working port and two additional thoracoscopic ports. The working port allowed the introduction of an endoscope, endoscopic instruments, and artificial graft and suture materials. The aorta was dissected using the robotic instruments and was clamped with two transthoracic clamps. After transaction of the aorta, a 20-mm polytetrafluoroethylene graft was cut and an end-to-end anastomosis was then performed with running 3-0 Prolene sutures with robotic instruments. The robotic system provides superior optics and allows for enhanced dexterity. Minimally invasive robotic replacement of the descending aorta is an effective procedure and may add benefits for both surgeon and patients.

Aorta, Thoracic↗
PubMed2005

Absorption-enhancing effect of glycyrrhizin induced in the presence of capric acid.

The absorption-enhancing effect of the simultaneous administration of sodium caprate (Cap-Na) and dipotassium glycyrrhizinate (Grz-K) was investigated to clarify an effect of Grz-K. A combination of 0.1% (w/v) Cap-Na and 2% (w/v) Grz-K had a rapid and long-lasting absorption-enhancing activity in Caco-2 cell monolayers under conditions where Cap-Na and Grz-K showed a weak and no activity, respectively. The simultaneous treatment of a Caco-2 cell monolayer with Cap-Na and Grz-K showed no change in intracellular calcium ion level, although a major mechanism of absorption-enhancing effect for Cap-Na was elevation of intracellular calcium ion level. On the other hand, the simultaneous enhancing effect of Cap-Na and Grz-K was inhibited by H7, a PKC inhibitor. Possibly, Grz-K showed an absorption-enhancing effect via PKC cellular signaling pathway after penetration into cell according to increasing membrane permeability by Cap-Na. The absorption of sCT by the rat colon was enhanced by a combination of 0.1% (w/v) Cap-Na and 2% (w/v) Grz-K, and its effect continued even 9h after the onset of the experiment. Furthermore, the simultaneous treatment of 0.1% (w/v) Cap-Na and 2% (w/v) Grz-K showed a negligible histological changes to the colon mucosal membrane and a negligible toxicity on Caco-2 cell monolayer. A combination of Cap-Na and Grz-K shows a synergistic absorption-enhancing effect with little mucosal injury, which is applicable to colon-specific delivery.

Absorption↗
PubMed2005

Off-pump CABG with synchronized arterial flow ensuring system.

PURPOSE: We developed a synchronized, arterial-flow, ensuring system to perform coronary anastomoses safely without any ischemia-related event. DESCRIPTION: Arterial blood is removed from the femoral artery. The resulting blood passes a switching valve and is pumped out to a syringe pump. This pump controller provides pulsatile arterial blood flow synchronized with the diastolic phase on an electrocardiogram. The arterial blood is perfused to the coronary artery through a fine flexible cannula during anastomosis. EVALUATION: From February 1999, 524 consecutive patients were operated on using the synchronized arterial flow ensuring system. Mean duration for each anastomosis was 7.6 +/- 3.3 minutes (range, 4 to 20 min). There were no intraoperative fatal arrhythmias, ventricular arrhythmias, or short-run or hemodynamic deterioration during anastomoses. No hospital death was observed, and postoperative myocardial infarction occurred in 2 patients (0.4%). Postoperative angiography showed a 98.1% patency rate. CONCLUSIONS: The early clinical and angiographical results for off-pump CABG with the synchronized arterial flow ensuring system were excellent without mortality. We believe that off-pump CABG can be more safely performed using the synchronized arterial flow ensuring system based on our favorable results.

Aged↗
PubMed2005

Distal embolus protection with an intra-aortic filter during stent-graft repair of a severely atherosclerotic thoracic aortic aneurysm.

PURPOSE: To assess the technical feasibility and efficacy of distal embolus protection with an intra-aortic filter during stent-graft repair in a patient diagnosed with a shaggy aorta. TECHNIQUE: In a 75-year-old man with a severely atherosclerotic thoracic aortic aneurysm, stent-graft repair was combined with transposition of the arch branches to the ascending aorta under thoracotomy. A filtration-type embolus protection device with a nitinol basket and polyester fabric was introduced through a 12-F sheath and opened in the supraceliac aorta during the stent-graft procedure; it was safely pulled back into the sheath after the stent-grafts were implanted. The stent-graft repair was successful, and abundant atheromatous debris was captured in the filter. Neither procedure-related embolic events nor neurological deficits were observed. CONCLUSIONS: Use of the intra-aortic filter device to prevent distal embolism during thoracic stent-graft repairs may be feasible and efficacious in severely atherosclerotic patients.

Aged↗
PubMed2004

Acinic cell carcinoma of the trachea: report of a case.

Acinic cell carcinoma (ACC) is a very rare primary tracheal carcinoma. We report a case of primary ACC of the trachea, which represents, to the best of our knowledge, only the fifth such case ever documented. Pharyngolaryngoesophagectomy was necessary for complete resection because the tumor invaded the trachea widely, up to the cricoid cartilage and involving the cervical esophagus. Although invasion of the upper aerodigestive tract by neoplasma is rare, to achieve complete resection and an acceptable prognosis, even a tumor with low malignancy requires wide resection.

Carcinoma, Acinar Cell↗
PubMed2004

Simultaneous monitoring of somatosensory evoked potentials and regional cerebral oxygen saturation combined with serial measurement of plasma levels of cerebral specific proteins for the early diagnosis of postoperative brain damage in cardiovascular surgery.

Combined somatosensory evoked potential (SEP) and regional brain oxygen saturation (rSO(2)) monitoring and simultaneous measurement of plasma levels of S100Beta and creatine kinase-isozyme BB (CK-BB) were performed to evaluate how reliable these diagnostic modality complexes are in the early prediction of neurological complications after surgery. Between 1999 and 2002, intraoperative SEP and rSO(2) monitoring combined with measurements of S100Beta and CK-BB levels in blood were performed in 82 consecutive patients undergoing cardiovascular operations with cardiopulmonary bypass (CPB). Twelve (14.6%) of these patients were diagnosed as having neurological complications after surgery; seven with transient neurological dysfunction (8.5%), and five with permanent stroke (6.1%). Twenty one of 82 patients in whom rSO(2) was recorded were judged abnormal; however, only nine of the 21 (42.9%) were diagnosed as having brain damage - diagnostic sensitivity and specificity being 75.0% and 82.9%, respectively. All six patients who showed abnormal SEP during surgery had neurological complications, but normal SEP was recorded in six other patients with apparent evidence of neurological complications - diagnostic sensitivity and specificity being 50% and 100%, respectively. There were no significant differences in S100Beta levels between patients with and without brain complications at 1 h and 24 h after CPB, but significant differences were detected in CK-BB levels at 24 h after CPB. In conclusion, simultaneous abnormalities detected in SEP and rSO(2) are highly predictive of cerebral neurocirculatory disturbances, but they are not so sensitive in diagnosing restricted focal cerebral lesions. Additional determinations of blood CK-BB levels might be valuable only to confirm the newly established brain complications.

Adult↗
PubMed2003

Matrix metalloproteinase-9 and urokinase-type plasminogen activator in varicose veins.

The purpose of this study was to evaluate the roles of matrix metalloproteinases (MMPs) and urokinase-type plasminogen activator (uPA) with regard to varicose veins (VVs). Immunohistochemical staining and ELISA were performed on samples from 73 patients with the following leg VVs: 82 greater saphenous veins (GSV) from the groin (GSV groin), 28 GSV from the ankle (GSV ankle), 85 VVs, and 13 normal GSV groin (control [CR]) obtained during coronary artery bypass surgery. Immunohistochemically, MMP-9 was localized in the smooth muscle cells (SMCs) in the tunica media. The ratio of immunopositive cells of MMP-9 in the GSV groin, VVs, and GSV ankle were significantly higher than that of CR. The ratios of immunopositive cells of uPA and uPA receptor (uPAR) were not significantly different among the groups. uPA and uPAR were found to be positive in a different set of SMCs of the MMP-9-positive cells. An ELISA showed that the amount of uPA in the culture of the GSV groin was significantly higher than that in CR. For the remodeling process, MMP-9 may be produced in the VV wall and degrade elastic lamellae and other extracellular components of the venous wall. uPA may be produced by groin tissue of the GSV and flow downward because of valvular incompetence, activating MMP-9 at VV tissues.

Adult↗
PubMed2003

Clinical application of a curved nitinol stent-graft for thoracic aortic aneurysms.

PURPOSE: To evaluate the clinical efficacy of a curved nitinol stent-graft for repair of thoracic aortic aneurysms. METHODS: The Matsui-Kitamura stent-graft (MKSG), composed of a self-expanding nitinol stent and polyester fabric, was shaped to match the aortic curvature of 11 patients (6 men; mean age 72.6 years, range 33-90) with 6 true and 5 false aneurysms of the distal arch or proximal descending aorta. The delivery system was an 18 or 20-F J-shaped sheath combined with a preloader-type introducer. The original mean proximal neck length was 16.4 mm, but 4 patients received an axilloaxillary bypass to lengthen the neck. Although the mean corrected proximal neck length was 21.9 mm (overall), 5 cases still had proximal necks <15 mm long. RESULTS: All curved MKSGs were successfully deployed in the correct position and fitted to the curvature of the aortic arch, achieving complete aneurysm exclusion in 8 (73%) cases. The other 3 repairs displayed early endoleaks; 1 received an additional MKSG, but the other 2 are being observed. Thirty-day mortality was 0%. One patient developed transient renal failure requiring hemodialysis; no neurological complications were observed. CONCLUSIONS: Endovascular repair of thoracic aortic aneurysms using curved MKSGs appears to be feasible and clinically effective. A tighter fit of the device to the curvature of the aortic arch may exclude distal arch aneurysms despite a short proximal neck.

Adult↗
PubMed2002

Real-time and continuous monitoring of myocardial blood flow using a thermal diffusion method.

OBJECTIVES: There has been no method which can measure regional myocardial blood flow in real-time and continuously. The purpose of this study was to validate myocardial blood flow measurement using a thermal diffusion method. For this purpose, myocardial blood flow measurement was performed using the thermal diffusion method and the electrolytic hydrogen clearance method. METHODS: Seven pigs were used for this study, six were for comparison between the thermal diffusion and electrolytic hydrogen clearance methods, and one was for demonstration of myocardial blood flow measurement using the thermal diffusion method on a beating heart coronary artery bypass model with ischemic preconditioning. RESULTS: A good correlation was found between myocardial blood flow values obtained by the electrolytic hydrogen clearance method and 1/V values obtained by a thermal diffusion probe, the correlation coefficient was 0.841 (P<0.001). During the beating heart coronary artery bypass, the regional myocardial blood flow was recorded in real-time and continuously. CONCLUSIONS: This study demonstrated measurement of regional myocardial blood flow using the thermal diffusion method for the first time and simultaneous measurement using the electrolytic hydrogen clearance method for calibration. It provided a real-time and continuous myocardial blood flow measurement and has a potential to contribute to progress in beating-heart surgery.

Animals↗
PubMed2002

Anticoagulant therapy after prosthetic valve replacement -optimal PT-INR in Japanese patients-.

Values of the international normalized ratio of prothrombin time (PT-INR) were analyzed at the time when anticoagulant-related complications developed in patients undergoing prosthetic valve replacement so as to evaluate the optimal therapeutic range in PT-INR value in Japanese patients. A total of 102 patients with a prosthetic heart valve who have been followed up at our department during the past 25 years were enrolled in this study. PT-INRs were determined regularly in these patients for the period between October 1996 and March 1999. Although no thromboembolic complications occurred during the period of this study, hemorrhagic complications developed in 26 (25.5%) patients. Three (2.9%) patients suffered from life threatening bleeding, such as cerebral bleeding and gastrointestinal bleeding and were defined as the major hemorrhagic group. Another 23 (22.5%) patients had minor bleeding complications such as nasal, gingival or subcutaneous bleeding and were defined as the minor hemorrhagic group. Mean PT-INR values were 3.8 2.0 and 3.2 1.0 at the onset of the complications in major and minor hemorrhagic groups, respectively, and there was no significant difference between the two groups. However, mean PT-INR values in the minor bleeding group differed significantly from that in a patient group with no hemorrhagic complications (N=76). Among the cases with bleeding complications, only 19% of the patients belonged to the range below 2.5 of PT-INR value and 54% of the patients were included in the range from 2.5 to 3.5 (p<0.05). In conclusion, the optimal therapeutic range between 2.5 and 3.5 in PT-INR recommended by the American Heart Association for patients with a prosthetic heart value in Western countries may be too high in Japanese patients. PT-INR below 2.5 is considered to be safe to prevent hemorrhagic complications.

Adult↗
PubMedDate not supplied

An experimental study of a new pull-through technique for aortic arch aneurysm in a porcine model.

A new pull-through technique for placement of the aortic arch stent-graft was developed. Self-expandable curved stents (Matsui-Kitamura stents) were used on 4 pigs. With use of the endoscopic system, the sheath insertion was performed at the ascending aorta. By this pull-through method from the ascending aorta to the femoral artery, the stent was deployed into the aortic arch. All stents were successfully deployed into the correct position, and they fitted into the curvature of the aortic arch wall. By this method, stent-grafting for aortic arch aneurysm is expected to be performed with more accuracy and safety.

Animals↗