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Biomedical subjects

A Nogawa

Publications and source records attributed to A Nogawa.

12 recordsLinked to original sources
PubMed1997

Clinical evaluation of pulsatile flow mode of Terumo Capiox centrifugal pump.

The Terumo Capiox centrifugal pump system possesses an automatic priming function in which the motor repeatedly stops and runs intermittently to eliminate air bubbles in the circuit through the micropores of the hollow-fiber membrane oxygenator. By modifying this mechanism, we have developed a pulsatile flow mode. In this mode, maximum and minimum pump rotational speeds can be independently set every 20 rpm in the range of 0 to 3,000 rpm. The duration of the pump run at maximum and minimum speeds can also be independently set every 0.1 s in the range of 0.2 to 15 s. In a clinical trial, after obtaining the desired flow rate, 2.4 L/min/m2 in nonpulsatile flow mode, a pulsatile flow mode of 60 cycles/min (with 1 cycle being maximum speed for 0.4 s and minimum speed for 0.6 s) was obtained by adding and subtracting 500 rpm to and from the rotational speed in nonpulsatile flow mode. Pulse pressures in the femoral artery and in the circuit just proximal to the perfusion cannula (6.5 mm Sarns high flow cannula with metal tip) were measured in 5 patients who underwent pulsatile cardiopulmonary bypass (CPB) for a coronary artery bypass graft (CABG), and compared to pulse pressures obtained by intraaortic balloon pumping (IABP) in 3 patients and by the pulsatile mode of the 3M Delphin pump in 3 patients. The platelet count, free hemoglobin, and beta-thromboglobulin (beta-TG) were measured and compared with measurements from another 5 patients who underwent nonpulsatile CPB. Although the pulse pressure measured in the circuit was 180 mm Hg on average, the pressure in the femoral artery was only 15 to 40 mm Hg with a mean of 20 mm Hg. In the same patients, 60 to 80 mm Hg pulse pressure was obtained with IABP. The pulse pressure obtained with the Delphin pump was not more than that obtained with the Terumo pump. There were no significant differences in percents of preoperative levels of platelet counts (pulsatile, 87.6 +/- 15.8% and nonpulsatile, 72.4 +/- 40.6%), free hemoglobin (pulsatile, 18 +/- 8 mg/dl and nonpulsatile, 25 = 7 mg/dl), and beta-TG (pulsatile 298 +/- 28 ng/ml and nonpulsatile, 312 +/- 143 ng/ml). In conclusion, although the pulsatile mode of the Terumo centrifugal pump did not exhibit any adverse effects hematologically, the pulse pressure obtained was unsatisfactorily small, mainly because of dumping caused by the perfusion cannula.

Angina Pectoris↗
PubMed1996

Effects of surface roughness on mechanical hemolysis.

Previous in vitro hemolysis test results showed that an inlet taper or a round corner in the leading edge of a stenotic connector played an important role in the reduction of hemolysis. However, computational fluid dynamics (CFD) analysis of these results indicated that the shear rate and hemolysis level were not always related to each other. Then, further research was performed, focusing on the effects of surface roughness on hemolysis. The results thus far can be summarized as threefold. First, the rate of hemolysis occurring at an abrupt change in the stenotic section was different if the longitudinal length of the stenosis was changed. The level of plasma-free hemoglobin after 6 h of circulation was decreased from 280 mg/dl to 70 mg/dl when the longitudinal length was shortened from 15 mm to 1 mm. Second, a comparison of hemolysis rates in identical stenotic connectors with differing surface roughness (Ra = 0.45 and 1.35 micrograms) revealed that a smooth surface achieved as much as an 80% reduction in the rate of hemolysis. Third, the in vitro hemolysis results obtained were further defined through CFD analysis.

Animals↗
PubMed1996

Clinical application of a newly developed autoflow control system for the Terumo centrifugal pump: from external control to built-in direct control.

We have developed an autoflow control system for the Terumo Capiox centrifugal pump, the SP-101. First, we made an external control system regulated by a personal computer through a serial communications line. Although an in vivo experiment using a goat showed excellent performance in regulating the flow, a communication error that caused an abrupt and instantaneous flow fluctuation was noted occasionally. Therefore, we incorporated a check-sum function to solve this problem. After this improvement, 5 patients safely underwent cardiopulmonary bypass using a pump having this autoflow control. As the next step for more practical usage, we developed a built-in autoflow control system in which the control device is entirely incorporated into the console without a communications line. This system demonstrated better response and reliability than the external control system and was applied successfully in 3 patients. In conclusion, this autoflow mode will expand the usage of centrifugal pumps through improved handling.

Algorithms↗
PubMed1994

The margin of safety in the use of a straight path centrifugal blood pump.

A new centrifugal blood pump with a rotor that arranges 6 straight paths radially was developed for open heart surgery and temporary circulatory support. We describe comparative studies of the margin of safety in the practical use of the new pump. This pump was evaluated for temperature increase, cavitation, and pressure sensitivity. Two commercially available centrifugal pumps, the Biomedicus cone type and the Sarns 3M impeller type, were used as control pumps. The temperature increase in the new pump was four times slower than in the impeller pump when the outlet and the inlet of the pump was clamped. No sign of cavitation was observed when 0.1 ml air was introduced to the pump inlet under a negative pressure of 200 mm Hg in fresh bovine blood. As for pressure sensitivity of centrifugal pumps in practical applications, circuit resistance was a more essential factor than flow-pressure curves of the pump.

Animals↗
PubMed1994

Peptic ulcer disease mortality. Comparison of native Japanese, Japanese Americans, and Caucasian Americans.

Peptic ulcer disease mortality patterns of California Japanese are compared with those of their home and host countries for even years from 1960 to 1988, as well as 1989. Data presented are consistent with the hypothesis that Helicobacter pylori is a necessary but not sufficient causal factor in peptide ulcer disease, and that other co-factors including cigarette smoking and salt intake may be important. Deaths due to peptic ulcer numbered 106 among California Japanese, 12,793 for California Caucasians, 107,461 in Japan, and 117,737 for United States Caucasians during the study period. Data for California Japanese were analyzed separately for California Japanese migrants (i.e., those born in Japan) and U.S.-born California Japanese. California Japanese exhibit site-specific peptic ulcer mortality patterns more similar to those of Japan than of the United States. California Japanese migrants (gastric ulcer:duodenal ulcer = 3.2:1), like Japanese in Japan (gastric ulcer:duodenal ulcer = 6.8:1), die more often from gastric than duodenal ulcer, while California and U.S. Caucasians die as often from duodenal ulcer as gastric ulcer (gastric ulcer:duodenal ulcer = 1:1). California Japanese born in the United States exhibit a ratio between those of California Japanese migrants and California Caucasians (gastric ulcer:duodenal ulcer = 2.3:1). U.S.-born California Japanese have the lowest age-adjusted mortality rates for duodenal ulcer and the second-lowest gastric ulcer rates of all populations examined, even though their gastric to duodenal ratio is similar to that for Japan (which has the highest overall ulcer mortality rate).

Adolescent↗
PubMed1993

A straight path centrifugal blood pump concept in the Capiox centrifugal pump.

This article describes comparative studies of a newly developed "straight path" centrifugal pump (Capiox centrifugal pump) targeted for open-heart surgery and circulatory support. A unique straight path design of the rotor was very effective in reducing the pump's rotational speed and prime volume. This pump was evaluated for hydraulics, hemolysis, depriming characteristics, cavitation, and heat generation. Two commercially available centrifugal pumps, the Biomedicus cone-type pump and the Sarns 3M impeller-type pump, were used as controls. The new pump required the lowest pump speed to produce the same flow rates under the same pressure loads and demonstrated the lowest hemolysis and the lowest temperature rise with the outlet clamped. The air volume required to deprime the new pump was one-third to one-half that for the other pumps, and no sign of cavitation was observed even if a small amount of air was introduced to the pump inlet under a negative pressure of 200 mm Hg.

Animals↗
PubMed1989

[Study on the dynamic behavior of mandibular distal-extension removable partial denture utilizing finite element method. 2. Influence of the location of rest and displaceability of residual ridge mucosa].

The purpose of this study is to investigate the denture design and displaceability of residual ridge mucosa and its relation to the load distribution on the remaining oral structures. In this study, the effects of the location of rest and displaceability of the mucosa were demonstrated utilizing the two-dimensional non-linear analysis reported on Part 1. The results were as follows. 1. Mesial rest could be simulated on the finite element model using pin element. 2. Removable partial denture with mesial rest distributed more stress on the mesial abutment teeth than that with distal rest. 3. Lesser displaceability of residual ridge mucosa resulted in a decrease of stress concentration around the most distal abutment and the uniform stress distribution on residual ridge was increased. 4. In the simulated condition where an increased pressure was applied on the mucosa, the behavior of the saddle on the mucosa with large displaceability could be similar to that of the mucosa with small displaceability. The results of this study suggested that mesial rest on the most distal abutment and pressure impression was desirable in removable partial denture with distal-extension.

Alveolar Process↗
PubMed1989

[Study on the dynamic behavior of mandibular distal-extension removable partial denture utilizing finite element method. 1. Introduction of two-dimensional non-linear analysis].

Recently there have been a number of studies concerning the dynamic behavior of removable partial denture under the loading, but none of previous studies have dealt with non-linear analysis. The purpose of this study is to demonstrate the usefulness of two-dimensional non-linear analysis. The behavior of abutment teeth and saddle in relation to the distribution of force on the teeth and the supporting tissues are the objects of this analysis. In this study, a comparative analysis between non-linear and linear analysis was performed utilizing finite element method. The results were as follows. 1. A two-dimensional model simulating the behavior of teeth and the supporting tissues in vitro could been made by changing the values of the Young's modulus and Poisson's ratio of the periodontal membranes and the mucosa of edentulous alveolar ridge at two stages. 2. In the conditioned high loading (5 kg), displacement of abutment teeth and saddle in the linear analysis was larger than that of the non-linear analysis. 3. In the conditioned high loading (5 kg), the distribution of the force on the mesial abutments in linear analysis was larger than that of non-linear analysis. The results of this study suggested that the non-linear analysis was desirable in the conditioned masticatory and biting force.

Dental Abutments↗
PubMedDate not supplied

Evaluation of a new heparin bonding process in prolonged extracorporeal membrane oxygenation.

A novel heparin bonding method has been developed for in situ surface modification using ozone oxidation, and evaluated in vitro and in vivo during prolonged extracorporeal membrane oxygenation (ECMO) experiments. The ECMO system consisted of a Capiox hollow fiber membrane oxygenator (MO; Terumo Corp., Tokyo, Japan) with an integral heat exchanger, a Capiox centrifugal pump (CP), and an extracorporeal circuit. The blood contacting surfaces of the system were completely modified using the heparin bonding process, and evaluated in a chronic sheep model for extended period of time, ranging from 96 to 168 hr, under minimal systemic heparinization. The heparin bonded surface was able to maintain high levels of heparin bioactivity, and showed improved blood compatibility in in vitro epifluorescent video microscopy experiments by suppressing platelet adhesion/activation and complement activation. For the ECMO experiments, extracorporeal blood flow was maintained at 3 L/min and the activated clotting time was maintained at 150 sec. There was no significant change in the gas transfer capability or mean pressure drop across the MO over experimental times of up to 168 hr. Platelet count and other coagulation parameters remained stable within the physiologic range throughout the experiment. There were no detectable thrombi in the CP, tubing, or connectors in the test circuit. Local thrombus formation was noted in a stagnant area of the MO, although this did not interfere with its function or lead to any significant embolization. Based on these results, the heparin bonded ECMO system appears to be a safe and effective device for prolonged extracorporeal circulation under minimal systemic heparinization.

Animals↗
PubMedDate not supplied

Can heparin immobilized surfaces maintain nonthrombogenic activity during in vivo long-term implantation?

The authors previously demonstrated that heparin immobilized surfaces showed excellent nonthrombogenic properties for extracorporeal membrane oxygenation experiments as long as 168 hr. The characteristics of the heparin immobilized surfaces include high heparin bioactivity and prevention of platelet adhesion and complement activation. However, it is not known whether the heparin immobilized surfaces would be effective for in vivo long-term implantation. Heparin bioactivity may be lost because of complete degradation or blocking of binding sites on heparin by adsorbed proteins. This study attempted to elucidate the in vivo long-term fate of heparin immobilized surfaces. The blood contacting surfaces of the ventricular assist device (VAD) made from polyurethane was modified with heparin immobilization and evaluated in a long-term sheep left VAD (LVAD) model for as long as 3 months. After removal of the VAD, heparin bioactivity was measured by Factor Xa assay. The blood contacting surfaces were analyzed with a scanning electron microscope, and the adsorbed proteins on the surfaces of the diaphragm were analyzed by SDS-PAGE and Western blotting. The thickness of adsorbed proteins on the surfaces also was measured by a confocal laser microscope. For the control ventricular assist devices, thrombus formation was observed within 1 month, whereas heparin immobilized VADs were able to operate thrombus free for periods as long as 3 months. The control surfaces demonstrated a thick adsorbed protein layer on thin surfaces, whereas heparin immobilized surfaces maintained thinner adsorbed proteins on thin surfaces. Anti Factor Xa activity of the heparinized surfaces disappeared after 15 days, but the surfaces remained nonthrombogenic even after heparin bioactivity was completely lost. The protein composition analyzed by SDS-PAGE showed an albumin dominant pattern on the heparinized surfaces. The band of 110 kD corresponding to C3b was detected only on the control surfaces, which possibly activated complement, and subsequently activated platelets and coagulation. Immunoblot showed degradation products of fibronectin and vitronectin on the control surfaces, which probably were promoted by surface generated protease, whereas the heparinized surfaces showed minimal degradation throughout the experimental periods. These results suggest that the heparin moiety has an ability to control adsorbed proteins, thereby inhibiting thrombus formation during in vivo long-term implantation.

Adsorption↗