Biomedical subjects

S Nitta

Publications and source records attributed to S Nitta.

At least 73 records · Page 4Linked to original sources

PubMed1998

Development of vibrating flow pump for left ventricular assist circulation.

Vibrating flow pump (VFP) can generate high frequency oscillated blood flow within 10-40 Hz. In this study, new type VFP was developed as a ventricular assist device. Left Ventricular assist circulation using VFP were performed as aseptic animal experiments using goats. hemodynamic parameters were recorded continuously at awake state. Driving frequency of VFP was 25 Hz and pump flow rate was controlled to approximately 2 l/min. Frequency of VFP was 25 hz and pump flow rate was controlled to approximately 2 L/min. Frequency analysis method was used for analyzing hemodynamics. The peak of power was observed at 25 Hz from the Fourier transformation of blood flow waveform. Systemic vascular resistance was decreased by the start of left ventricular assistance using oscillated blood flow. No fatal arrhythmia was observed during this study. As the conclusion, new type VFP has a sufficient performance for left ventricular assistance. Small size blood pump may be enabled by the oscillated blood flow because VFP is driven at high frequency moving with short stroke volume.

Animals↗

PubMed1998

Development of total artificial heart with economical and durability advantages.

To develop a total artificial heart (TAH) pump system, we created a design paying particular attention to durability and cost. We adopted a pneumatically driven sac type artificial heart, where the configuration of the sac was decided according to the methodology of flow visualization. Its configuration is almost round to achieve as little stagnation as possible and a low turbulent flow. The main body of the sac was made using polyvinyl chloride (PVC) paste. The paste was poured into an external mold, and heated in a hot air drying oven. Coating was performed using polyurethane. The basic performance of this pump system was tested using a model circulation circuit, and a fitting study through acute animal experiment, using a healthy adult goat, was carried out. As for the TAH produced experimentally, a pump output exceeding 5.0 l/min in the model circulation circuit was provided. Implantation in the internal pleural cavity of a healthy adult goat, 55 kg in weight, proved possible and quite easy in comparison. It is thought that a more refined design in the connector part is desirable. Furthermore, a chronic experiment with the TAH will be carried out, and examination will need to be repeated in the future.

Animals↗

PubMed1998

Monitoring system for the totally implantable ventricular assist system by use of sensors for virtual reality.

For the development of the totally implantable artificial organs, it is an important problem to monitor the conditions of the implantable devices, especially when used in clinical cases. In this study we used position sensors for the 3-dimensional (3-D) virtual reality (VR) system monitor an implantable artificial heart. The sensors used in the experiments were 3-space Fastrak (Polhemus, USA). The position sensors using electro-magnetic forces were attached to the inner actuating zone. Sensitivity of the position sensors was in the order of around 0.8 mm. By use of these VR position sensors, we could easily detect the six degrees of freedom as x,y,z, and pitch, yaw, roll of these sensors. Experimental evaluation using a model circulation loop and healthy adult goats was performed. Experimental results suggest that our newly developed implantable sensors for monitoring the implantable artificial heart system were useful for sensing driving condition, thus possibly useful for the implantable devices for clinical usage.

Animals↗

PubMed1997

Characterization of renal angiomyolipoma by scanning acoustic microscopy.

A scanning acoustic microscope system was used to differentiate renal angiomyolipoma from renal cell carcinoma. The ultrasonic frequency used ranged from 100 to 200 MHz, and the attenuation constant and sound speed were measured on a two-dimensional distribution. The sound speed was significantly lower for lipoma cells than for vessels, smooth muscle fibres, clear cell renal cancer or granular cell renal cancer. The attenuation constant was significantly lower for lipoma cells than for vessels or clear cells. Both acoustic parameters for smooth muscle fibres were significantly lower than for vessels. The heterogeneity of the microacoustic field in renal angiomyolipoma is closely related to the high intensity echo observed on clinical echography. Renal angiomyolipoma and renal cell carcinoma can thus be distinguished by acoustic examination.

Angiomyolipoma↗

PubMed1997

Acoustic properties of dialysed kidney by scanning acoustic microscopy.

BACKGROUND: A correlation between acquired renal cysts in the dialysed kidney and renal cancer has long been debated, but no changes in the physical properties of kidneys at the microscopic level have been reported. The purpose of the present study was to classify the physical properties of the kidneys of patients undergoing haemodialysis at several stages of pathology by use of the scanning acoustic microscope. METHODS: Sixteen surgically excised kidneys of dialysis patients were investigated. Tissues were fixed in 10% formalin, frozen in acetone, and cut 10 microns thick on a cryostat. We used a scanning acoustic microscope operated in the frequency range of 100-200 MHz. Attenuation constant and sound speed were measured on a two-dimensional distribution. RESULTS: The attenuation constant for inflammatory granulation tissue was significantly higher than that for hyaline degeneration tissue (P < 0.001). Sound speed was high for granulation tissue, but tended to diminish gradually for hyaline degeneration. Sound speed increased again with progression to cystic degeneration (P < 0.001), but the attenuation constant remained low. When a cystic kidney contained a malignant lesion, the previously low attenuation constant rose at that site (P < 0.001), and the previously high sound speed was diminished (P < 0.001). CONCLUSION: Our data suggest that the physical properties of dialysed kidneys at different stages of pathology can be classified by their acoustic properties. Simultaneous evaluation of attenuation constant and sound speed is considered applicable to determining whether tissues contain malignant elements.

Acoustics↗

PubMed1997

Predicting difficult intubation with indirect laryngoscopy.

BACKGROUND: It is not always possible to predict when tracheal intubation will be difficult or impossible. The authors wanted to determine whether indirect laryngoscopy could identify patients in whom intubation was difficult. METHODS: Indirect laryngoscopy was done in 2,504 patients. The Wilson risk sum score and the modified Mallampati score were also studied in a different series of 3,680 patients for comparison. These predictive methods were compared according to three parameters: positive predictive value, sensitivity, and specificity. RESULTS: Of 6,184 patients studied, the trachea proved difficult to intubate in 82 (1.3%). Positive predictive value (31%) and specificity (98.4%) with indirect laryngoscopy were greater than the other two predictive methods (P < 0.01), whereas sensitivity with indirect laryngoscopy (69.2%) was greater than that of the Wilson risk sum score (55.4%) (P < 0.01). CONCLUSIONS: Although in 15% of patients indirect laryngoscopy could not be performed because of excessive gag reflex, indirect laryngoscopy can serve as an effective method to predict difficult intubation.

Adult↗

PubMed1997

Nonlinear mathematical analysis of the hemodynamic parameters during left ventricular assistance with oscillated blood flow.

For the development of a totally implantable ventricular assist system (VAS), we have been developing the vibrating flow pump (VFP), which can generate oscillated blood flow with a relatively high frequency (10-50 Hz) for a totally implantable system. In this study, effects of left ventricular assistance with this unique oscillated blood flow were analyzed by nonlinear mathematics for evaluation as the entire circulatory regulatory system, not as a separate part of the system. Left heart bypasses using VFPs from the left atriums to the descending aortas were performed in chronic animal experiments using healthy adult goats. Electrocardiogram (ECG), arterial blood pressure, VFP pump flow, and flow of the descending aorta data taken while the goats were awake were recorded in the data recorder and analyzed in the personal computer system through the AD convertor. Using nonlinear mathematics, time series data were embedded into the phase space, and the Lyapunov numerical method, fractal dimension analysis, and power spectrum analysis were performed to evaluate the nonlinear dynamics. During left ventricular assistance with the VFP, Mayer wave fluctuations were decreased in the power spectrum, the fractal dimension of the hemodynamics was significantly decreased, and peripheral vascular resistance was significantly decreased. These results suggest that nonlinear dynamics, which mediate the cardiovascular dynamics, may be affected during LV bypass with oscillated flow. Decreased power of the Mayer wave in the spectrum caused the limit cycle attractor of the hemodynamics and decreased the peripheral resistance. Decreased sympathetic discharges may be the origin of the decreased Mayer wave and fractal dimension. These nonlinear dynamical analyses may be useful to design the optimal VAS control.

Animals↗

PubMed1997

Hemolysis test of disposable type vibrating flow pump.

The vibrating flow pump (VFP) can generate high frequency oscillated blood flow. Because of the high frequency driving with short stroke volume, the pump system can be small. The disposable type VFP (D-VFP) was developed for use for extracorporeal circulation. The electromagnetic actuator was detached from the vibrating tube, which was newly designed to be a disposable tube with a jellyfish valve. Hemolysis tests of the D-VFP, VFP, centrifugal pump, and roller pump were performed in a mock circulation study using goat blood. Plasma free hemoglobin was measured every 15 min under the same conditions. The plasma free hemoglobin of the D-VFP was 16 mg/dl although that of the VFP was 160 mg/dl at 30 min. The plasma free hemoglobin of the centrifugal pump and roller pump at 30 min were 3 mg/dl and 9 mg/dl, respectively. The hemolysis performance of the D-VFP may be studied further as a result of this study. Two important factors affecting hemolysis development may be the materials of which the vibrating tube is made and heat transmission from the actuator. The D-VFP has a smooth acrylic surface for blood contact compared with the metal surface of old type VFP. The electromagnetic actuator of the VFP surrounded the vibrating tube, so heat from the actuator could be easily transmitted to the blood. Because the D-VFP has a disposable vibrating tube that is detached from the actuator, heat is not readily transmitted to the blood. A mock circulation study of heat transmission was performed using the D-VFP and VFP. Results of the heat transmission study showed that the fluid temperature of the D-VFP was not increased and stayed at room temperature although that of the VFP increased approximately 1 degree C above room temperature. The D-VFP may be a good style for the development of the VFP for use for extracorporeal circulation.

Acrylates↗

PubMed1997

Development of a novel centrifugal pump: magnetic rotary pump.

The rotational axis of the centrifugal pump has some associated problems such as blood destruction and sealing between the axis and pump housing. To improve upon these deficits we have developed a new type of blood pump, the magnetic rotary pump (MRP). The MRP has an original design with no rotational axis and no impellers. We made a prototype MRP and examined its hemodynamics in mock circulation. The prototype MRP flow rate is only 1.0 L/min with an afterload of 30 mm Hg, and we have made some modifications in the size and drive mechanisms from these results. The modified MRP can achieve high flow rates and rotational speeds (6.0 L/min with an afterload of 100 mm Hg, 2,000 rpm) in a mock circuit, and the modified MRP was used for left heart assistance in an acute animal experiment. The MRP could maintain the hemodynamics of an anesthetized adult goat. These results suggest that the MRP needs to be improved in several areas, but the MRP may be useful as a blood pump.

Animals↗

PubMed1997

Pulmonary arterial impedance analysis by the use of the oscillated assist flow.

Pulmonary arterial impedance is an important and interesting characteristic that can be used to evaluate the physiological properties of the pulmonary vessel. However, power spectrum analysis of the pulmonary artery pressure and flow pattern have suggested that peak power in the relatively high frequency range (> 10 Hz) is significantly low; thus, we cannot analyze the vessel properties in the high frequency range. In this study, we used the newly developed vibrating flow pump (VFP), which can generate oscillated blood flow with a relatively high frequency (10-50 Hz) for right heart bypass, to evaluate the pulmonary arterial impedance pattern in the high frequency range. Acute animal experiments of the right heart bypass from the right atrium to the pulmonary artery using 6 healthy adult goats were performed. The flow pattern and pressure of the pulmonary artery, electrocardiograms (ECGs), and arterial and right atrial pressures were continuously monitored during the experiments. Spectral analysis of the hemodynamic parameters using the fast Fourier transform (FFT) method was performed to evaluate the spectral properties. The coherence function, transfer function, and phase patterns were calculated to analyze the impedance pattern in the relatively high frequency area. Previously, various investigators had tried to analyze the impedance patterns of the pulmonary artery; however, they could not analyze the impedance patterns over 10 Hz because the spectral patterns of the pulmonary flow do not have high power at high frequencies. These physiological analyses may be useful in designing the optimal pulmonary circulation.

Animals↗

PubMed1997

Effect of adenosine on adrenergic neurotransmission and modulation by endothelium in canine pulmonary artery.

To determine the effect of adenosine on adrenergic neurotransmission in pulmonary vasculature and its modulation by endothelial cells, we studied canine pulmonary arteries under isometric conditions in vitro. Adenosine decreased the contractile responses to electrical field stimulation but had no effect on those to norepinephrine. This inhibitory effect was concentration dependent, with a rank order of potency of NECA > 2-chloroadenosine > adenosine >> APNEA (an A3-adenosine-receptor agonist) > CGS-21680 (an A2a agonist) > CCPA (an A1 agonist). Adenosine reduced the electrical field stimulation-evoked 3H overflow in superfused pulmonary artery previously soaked in [3H]norepinephrine. Pretreatment with the adenosine uptake blocker dipyridamole or the adenosine deaminase inhibitor deoxycoformycin enhanced the adenosine action, and this enhancement was not observed in the endothelium-denuded tissues. Adenosine deaminase activity was found in endothelial cells. Therefore, adenosine inhibits norepinephrine release via an A2b-receptor mechanism, an effect that may be modulated by uptake and metabolism by endothelial cells.

Adenosine↗

PubMed1997

Effects of surfactant proteins SP-B and SP-C on dynamic and static mechanics of immature lungs.

To investigate the effects of surfactant proteins B (SP-B) and C (SP-C) on lung mechanics, we compared tidal and static lung volumes of immature rabbits anesthetized with pentobarbital sodium and given reconstituted test surfactants (RTS). With a series of RTS having various SP-B concentrations (0-0.7%) but a fixed SP-C concentration (1.4%), both the tidal volume with 25-cmH2O insufflation pressure and the static volume deflated to 5-cmH2O airway pressure increased, significantly correlating with the SP-B concentration: the former increased from 6.5 to 26.0 ml/kg (mean), and the latter increased from 6.4 to 31.8 ml/kg. With another series of RTS having a fixed SP-B concentration (0.7%) but various SP-C concentrations (0-1.4%), the tidal volume increased from 5.1 to 24.8 ml/kg, significantly correlating with the SP-C concentration, whereas the static volume increased from 3.4 to 32.0 ml/kg, the ceiling value, in the presence of a minimal concentration of SP-C (0. 18%). In conclusion, certain doses of SP-B and SP-C were indispensable for optimizing dynamic lung mechanics; the static mechanics, however, required significantly less SP-C.

Animals↗

PubMed1997

[Report on a case of adult rhabdomyosarcoma subjected to tumorectomy and lobectomy].

Rhabdomyosarcoma (RMS) rarely occurs in adult and intra thoracic activity. This is a report on a case we experienced of adult RMS, which was subjected to tumorectomy and lobectomy. The patient was a 23 years old male, who first consulted a hospital in his neighborhood due to anterior chest pain suffered since May 1995. Since the examination showed an abnormal shadow in right anterior mediastinum, the patient was referred to our department. By biopsy under CT, the patient was diagnosed as having embryonal type of RMS and underwent surgery. The outcome was good and the patient is currently in the course of chemotherapy using IRS (Inter-group Rhabdomyosarcoma study)-III.

Adult↗

PubMed1997

[Giant localized fibrous pleural mesothelioma accompanying lung metastasis--a case report].

We experienced a case of giant localized fibrous pleural mesothelioma accompanying lung metastasis. The patient was a 26-year-old woman, who was pointed out elevation of the left diaphragma by the chest roentgenogram in 1992 but left it as it was. In 1995, a giant tumor occupying 1/2 or more of the left thoracic cavity was detected by chest CT and MRI. A giant localized pleural mesothelioma was suspected since there was no accumulation in Ga scintigram and an operation was performed. The tumor originated without pedicle and with invasion of the lung from the pleura of the left S8 and it was excised by separating the left lower lobe at 7-cm distance from the tumor. The tumor was 20 x 12 x 11 cm in size weighing 1700 g and the histopathological diagnosis was localized fibrous pleural mesothelioma. A lung metastasis of 1.0 cm in size was found in a part of the left lower lobe resected at the same time. The postoperative course has been satisfactory and there is no sign of recurrence at present. There are occasional cases of recurrence associated with a localized fibrous pleural mesothelioma even though it is judged benign. In the present case, a metastatic focus was already present at the time of initial surgery and is considered a valuable case.

Adult↗

PubMed1997

[A case report of left postero-lateral thoracotomy for simultaneous CABG and left lower lobectomy].

Surgical management of patients with concomitant resectable lung lesions and critical cardiac disease is controversial. We report a case of concomitant pulmonary and cardiac surgery via a left thoracotomy. A 67-year-old male was admitted to our hospital complaining of recurrent bloody sputum and an abnormal shadow on chest X-ray. Chest CT and MRI showed a tumor in the left lower lobe (S10), with invasion of the diaphragm. A diagnosis of squamous cell carcinoma was obtained by transbronchial lung biopsy. The patient had a history of angina pectoris, and stress testing was positive. Coronary angiography showed 90% stenosis at segment 5, suggesting a risk of perioperative or postoperative myocardial infarction. This necessitated simultaneous surgical treatment for lung cancer and ischemic heart disease. A lobectomy of the left lower lung was performed, followed by coronary artery bypass grafting (CABG), using the great saphenous vein. The postoperative course was uneventful except for the occurrence of cholecystitis. Lung cancer and ischemic heart disease can be safely treated simultaneously via a single incision, with and benefit for selected patients.

Aged↗

PubMed1997

[A case of bloody sputum due to the migration of a temporary cardiac pacing lead into the bronchus].

A 60-year-old man with bloody sputum was admitted to our institute. Prior to the present admission, he had undergone coronary artery bypass graft surgery (GABG) at our institute 20 month earlier. The fiber optic bronchoscopy findings showed the cause of bleeding to be due to the migration of a post surgical temporary myocardial pacing lead which had been cut off at skin level after a CABG. Under general anesthesia we thus removed this migrated lead using both a fiber optic bronchoscope and forceps. The wire lead was easily removed and the patient has since suffered no more instances of bloody sputum.

Bronchi↗

PubMed1997

Development and evaluation of totally implantable ventricular assist system using a vibrating flow pump and transcutaneous energy transmission system with amorphous fibers.

We have developed a vibrating flow pump (VFP) that can generate oscillated blood flow with a relatively high frequency (10-50 Hz) for a totally implantable ventricular assist system (VAS). To evaluate the newly developed VAS, left heart bypasses, using the VFP, were performed in chronic animal experiments. Hemodynamic parameters were recorded in a data recorder in healthy adult goats during an awake condition and analyzed in a personal computer system through an alternating-direct current converter. Basic performance of the total system with a transcutaneous energy transmission system were satisfactory. During left ventricular assistance with the VFP, Mayer wave fluctuations of hemodynamics were decreased in the power spectrum, the fractal dimensions of the hemodynamics were significantly decreased, and peripheral vascular resistance was significantly decreased. These results suggest that cardiovascular regulatory nonlinear dynamics, which mediate the hemodynamics, may be affected by left ventricular bypass with oscillated flow. The decreased power of the Mayer wave in the spectrum caused the limit cycle attractor of the hemodynamics and decreased peripheral resistance. These results suggest that this newly developed VAS is useful for the totally implantable system with unique characteristics that can control hemodynamic properties.

Animals↗

PubMed1996

Influence of tissue preparation on the high-frequency acoustic properties of normal kidney tissue.

The influence of various tissue preparations on the acoustic properties of normal kidney tissue at high frequencies was investigated. Eight surgically excised normal kidney tissue specimens were classified into three groups: (i) fresh, frozen section, (ii) formalin-fixed, frozen section and (iii) formalin-fixed, paraffin section. Scanning acoustic microscopy operating in the frequency range of 100-200 MHz was used to display the two-dimensional distribution of attenuation constant and sound speed. Our results indicate that (i) there is no significant variation in both acoustic parameters between the three tissue groups, (ii) fixation by 10% formalin produces no significant change in the acoustic parameters, (iii) in fat-free tissue regions, the acoustic parameters are independent of preparation method and (iv) frozen sections must be used to assess the acoustic parameters in fat-rich tissues.

Histocytological Preparation Techniques↗