K Okamoto

Kumamoto University, Kumamoto, Kumamoto Prefecture, Japan

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Publications (21)13.33 Total impact

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    ABSTRACT: Nitric oxide (NO) is increasingly being used in medical applications. Currently, a gas cylinder of N2 mixed with a high concentration of NO is used in the NO inhalation system. However, this arrangement is potentially risky due to the possibility of accidental leak of NO from the cylinder. The presence of NO in air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore, an on-site generation of NO would be very desirable for patients with acute respiratory distress syndrome and other related illnesses. Previously, our group reported the production of NO using a pulsed arc discharge. In this work, the prototype of the on-site NO generator was developed and the performances of the NO generator were demonstrated for medical applications.
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    ABSTRACT: Nitric oxide (NO) is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder. The presence of NO in the air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore, an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease. To develop the NO inhalation system without a gas cylinder, which would include a high concentration of NO, NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge. In the present work, the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition. The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds. In addition, it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.
    Plasma Science and Technology 01/2008; 9(6):747. DOI:10.1088/1009-0630/9/6/26 · 0.60 Impact Factor
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    ABSTRACT: In 1987, Nitric oxide (NO) was identified as an effective treatment involving endothelium-derived relaxing factor (EDRF)<sup>1</sup>. NO has attracted lots of attention from the discovery. And now, NO is increasingly being used in medical treatments for some illness related lung. Currently a system of NO inhalation has a gas cylinder of N 2 mixed with a high concentration of NO. However, this method is potentially risky due to the possibility of accidental leak of NO from the cylinder. In addition, gas cylinder is too heavy to carry around and too expensive to be used for all patients. Therefore, an on-site generation of NO would be highly desirable for patient, who is suffering lung disease, and medical doctors. Previous researches reported that NO is produced by pulsed arc discharge in the mixture of N 2 and O 2 , and NO concentration increases with the increasing of pulse repetition rate and energy storage capacitance<sup>2–4</sup>. In this paper, the detail about a prototype of NO generator by pulsed arc discharge based on the optimal discharge condition has been reported. As the results, it is observed that NO concentration in the outlet gas is about almost 1000ppm and rise time is about 20 to 30 sec. These conditions are enough for NO inhalation therapy. Additionally, NO concentration is adjustable by changing pulse repetition rate.
    Pulsed Power Conference, 2007 16th IEEE International; 07/2007
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    ABSTRACT: In 1987, Nitric oxide (NO) was identified as an effective treatment involving endothelium-derived relaxing factor (EDRF)1. NO has attracted lots of attention from the discovery. And now, NO is increasingly being used in medical treatments for some illness related lung. Currently a system of NO inhalation has a gas cylinder of N2 mixed with a high concentration of NO. However, this method is potentially risky due to the possibility of accidental leak of NO from the cylinder. In addition, gas cylinder is too heavy to carry around and too expensive to be used for all patients. Therefore, an on-site generation of NO would be highly desirable for patient, who is suffering lung disease, and medical doctors. Previous researches reported that NO is produced by pulsed arc discharge in the mixture of N2 and O2, and NO concentration increases with the increasing of pulse repetition rate and energy storage capacitance2-4. In this paper, the detail about a prototype of NO generator by pulsed arc discharge based on the optimal discharge condition has been reported. As the results, it is observed that NO concentration in the outlet gas is about almost 1000ppm and rise time is about 20 to 30 sec. These conditions are enough for NO inhalation therapy. Additionally, NO concentration is adjustable by changing pulse repetition rate.
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    ABSTRACT: Nitric monoxide (NO) is increasingly being used in medical applications. Currently, a gas cylinder of N<sub>2</sub> mixed with a high concentration of NO is used. This arrangement is potentially risky due to the possibility of accidental leak of NO from the cylinder. The presence of NO in air leads to the formation of nitric dioxide (NO<sub>2</sub>), which is toxic to the lungs. Therefore, an on-site generation of NO would be very desirable for patients with acute respiratory distress syndrome and other related illnesses. We have recently reported on the production of NO using a pulsed arc discharge. In the present work, the discharge reactor was made simpler and smaller. NO was generated using a pulsed arc discharge in dry air and in mixtures of oxygen and nitrogen. The composition of the gas mixture after treatment with an arc discharge followed by exposure to heated molybdenum was 540 ppm of NO, 48 ppm of NO<sub>2</sub>, and the balance dry air at 0.1 MPa and 300 ± 3 K. No ozone was detected at the outlet of the system by UV absorption. The density of the brass particles emitted from the electrodes, which had diameters over 0.3 μm, was less than 1.39 μg/L. A filter could readily capture and thus remove the brass particles.
    IEEE Transactions on Plasma Science 11/2002; 30(5-30):1993 - 1998. DOI:10.1109/TPS.2002.807502 · 0.95 Impact Factor
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    ABSTRACT: The shortage of donor hearts has made use of non-beating hearts as cardiac grafts an attractive possibility for heart transplant candidates. The purpose of this study was to evaluate the utility of leukocyte-depleted hot shot cardioplegia for resuscitation of non-beating hearts obtained from asphyxiated dogs via an autoperfusing heart-lung circuit. Mongrel dogs were divided into 3 groups according to the warm ischemia time and the method of reperfusion before starting the autoperfusing heart-lung circuit. Group A (n=4) had 60 minutes of warm ischemia and reperfusion without leukocyte-depleted hot shot, Group B (n=5) had 30 minutes of warm ischemia and reperfusion with leukocyte-depleted hot shot, and Group C (n=7) had 60 minutes of warm ischemia and reperfusion with leukocyte-depleted hot shot. We calculated stroke work via the heart-lung circuit to evaluate cardiac function of the resuscitated hearts. The criteria for "recovery" has been reported elsewhere. Myocardial water content of the resuscitated hearts was also measured and analyzed. No inotropic agents were used. The recovery rates in groups A, B and C were 0%, 80% and 57%, respectively, and the group B rate was significantly higher than the group A rate (p=0.04). Although myocardial water content did not differ between groups B and C, it was significantly lower in recovered hearts than in non-recovered hearts (p=0.04). Significant negative correlation was observed between the maximum stroke work value and myocardial water content in the resuscitated hearts (r=0.668, p=0.03). The autoperfusing heart-lung circuit is useful for evaluation and maintenance of cardiac function. Our experimental data shows that leukocyte-depleted hot shot plays a great role for resuscitation and recovery of non-beating hearts.
    Annals of thoracic and cardiovascular surgery: official journal of the Association of Thoracic and Cardiovascular Surgeons of Asia 01/2002; 7(6):341-5. · 0.69 Impact Factor
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    ABSTRACT: Inhaled nitric oxide (INO) therapy is becoming an indispensable measure in some critically ill patients with pulmonary hypertension. Most importantly, it has been shown that INO significantly reduces the necessity for extracorporeal lung assist in newborns with hypoxemic respiratory failure and pulmonary hypertension. A large number of basic and clinical studies are making great steps in delineating its physiology, techniques, side effects, and clinical efficacy. This article reviews the current knowledge of INO therapy including a novel device of nitric oxide production system.
    Nippon rinsho. Japanese journal of clinical medicine 07/2001; 59(6):1126-31.
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    ABSTRACT: We reported a case of successful simultaneous mitral and aortic valvuloplasty using rasping procedure. A 55-year-old woman with combined valvular disease received this operation. Postoperatively, the mitral valve area increased from 1.15 cm2 to 2.03 cm2. Mitral regurgitation improved. Aortic valve pressure gradient decreased from 21 mmHg to 0 mmHg. Aortic regurgitation also improved. Cardiac Index (CI) increased from 1.94 l/min./m2 to 2.59 l/min./m2. Ejection fraction (EF) also increased from 60% to 82%. The postoperative course was uneventful. Excellent postoperative results of this procedure may be expected, not only in single valvular disease but also in combined valvular disease.
    Kyobu geka. The Japanese journal of thoracic surgery 06/2001; 54(5):419-21.
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    ABSTRACT: We compared the operative outcomes among 14 patients who underwent the removal of left atrial myxoma with four different approaches; right lateral (n = 2), transseptal bi-atrial (Dubost, n = 4), conventional transseptal (n = 4) and superior transseptal approach (STA, n = 4). Concomitant operations were performed in 4 cases (CABG, two; aortic valvuloplasty, one; mitral valve replacement, one), and two out of 4 cases were in the STA group. The mean operation, cardiopulmonary bypass and aortic cross-clamp times were shorter in the STA group compared to the other three group. The total amount of postoperative drain discharge and the peak value of creatine kinase were also lower in the STA group compared to the other three groups. Among the patients in sinus rhythm before operation, the use of STA was associated with a greater incidence (100%) of postoperative atrial fibrillation or junctional rhythm. These rhythm disturbances were temporary, and all returned to sinus rhythms during hospital stay. We conclude that STA is an excellent approach with a nice surgical view to expose and remove the left atrial myxoma.
    Kyobu geka. The Japanese journal of thoracic surgery 04/2001; 54(3):211-4.
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    ABSTRACT: We compared the effects a novel recombinant tissue-type plasminogen activator (rt-PA) E6010 with the more conventional therapeutic agent alteplase in a new canine model of life-threatening acute pulmonary thromboembolism (APTE). Fifty milliliters of autologous blood was obtained from anesthetized, adult mongrel dogs and mixed with 10,000 units of thrombin. The left pulmonary artery, pulmonary vein, and bronchus were ligated, and previously prepared blood clots were injected via the femoral vein until the mean pulmonary artery pressure (mPA) increased to 2.5-3.0 times over baseline mPA (control). E6010 (0.4 mg/kg) or alteplase (1.33 mg/kg) was administered to other animals following inducement of APTE. In control animals, 60 min after embolization, mPA increased from 13+/-3 mm Hg to 31+/-3 mm Hg (p < 0.0001), cardiac output (CO) decreased from 1.47+/-0.35 l/min to 1.15+/-0.39 l/min (p < 0.0001), and PaO2 decreased from 101+/-31 mm Hg to 65+/-20 mm Hg (p < 0.001). E6010 significantly reduced mPA from 31+/-3 mm Hg to 25+/-4 mm Hg (p < 0.0001) 30 min after administration. In the alteplase group, however, mPA did not significantly change. At 180 min following drug administration, further reduction of mPA was significantly observed in both treatments. CO and PaO2 did not improve after either treatment. The present study indicated that E6010 more rapidly reduced pulmonary hypertension in our APTE model. Because of its rapid action, E6010 might be a promising thrombolytic agent for treatment of APTE.
    Annals of thoracic and cardiovascular surgery: official journal of the Association of Thoracic and Cardiovascular Surgeons of Asia 10/2000; 6(5):299-303. · 0.69 Impact Factor
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    ABSTRACT: We report the results of long-term follow up in 9 patients who underwent pericardiectomy for constrictive pericarditis. In order to test whether if congestive liver dysfunction due to the disease could be reversible or not after the surgical repair, the patients were evaluated by indocyanine green (ICG) clearance test. All the patients improved in NYHA classification after long-term periods following surgical repairs. The percentage of ICG retention at 15 minutes (ICG-R15) improved in most of the patients. However, two patients who had a long history from the onset before surgery became worse in ICG-R15. From the above reports, reversibility of hepatic function might be dependent on the duration of liver congestion before surgical repairs.
    Kyobu geka. The Japanese journal of thoracic surgery 08/2000; 53(7):567-70.
  • Transplantation Proceedings 04/2000; 32(2):336-8. DOI:10.1016/S0041-1345(99)00973-2 · 0.95 Impact Factor
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    ABSTRACT: Nitric monoxide (NO) is widely used in medical treatment of acute respiratory distress syndrome (ARDS). The production of NO is of interest to the medical community. In the present work, NO is generated by pulsed discharges between two rod electrodes in a mixture of nitrogen and oxygen. An arc discharge having a temperature of about 10000 K was produced, which was sufficient to generate NO. Some of the important parameters affecting the production of NO have been investigated. These include the percentage of O<sub>2</sub> (6-94%) in the mixture of Na and O<sub>2</sub>, the energy of the discharge (0.5-12 J/pulse), the pulse repetition rate (0.54.5 pps) and the flow rate (1.35-5.4 l/min) of the gas mixture. NO<sub>2</sub> produced in the discharge was successfully changed to NO using a heated molybdenum tube, NO<sub>2</sub> must be extracted from the gas before clinical inhalation. The concentration of ozone was completely eliminated by bubbling the gas mixture through water. A maximum of NO and a minimum of NO<sub>2</sub> concentrations were generated when the proportion of O<sub>2</sub> in the gas mixture was in the range of 20-27%. The concentrations of NO and NO<sub>2</sub> increased with increasing pulse repetition rate and with decreasing flow rate of the mixture. In all cases, No<sub>2</sub> was effectively removed using a heated molybdenum tube
    IEEE Transactions on Plasma Science 03/2000; DOI:10.1109/27.842877 · 0.95 Impact Factor
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    ABSTRACT: A 16-year-old boy with acute respiratory distress syndrome (ARDS) due to near-drowning was admitted to our hospital. ARDS was treated with low-level nitric oxide (NO) inhalation (ranging from 4 ppm to 1 ppm) for 24 days. Oxygenation was improved and pulmonary hypertension was reduced after NO inhalation, but systemic blood pressure, heart rate, and cardiac output were not affected. PaO2 improved from 153 Torr to 354 Torr under identical ventilating conditions (F1O2 1.0), and mean pulmonary arterial pressure fell from 40 mm Hg to 27 mmHg. It has been reported that NO inhalation alleviates ventilation-flow mismatch and pulmonary hypertension. It is unclear, however, whether this therapy improves the prognosis for ARDS. In our patient, NO inhalation was effective in alleviating the oxygenation impairment and pulmonary hypertension associated with ARDS.
    01/2000; 37(12):997-1002.
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    ABSTRACT: We hypothesized that patients who have undergone hypothermic cardiopulmonary bypass may have abnormal oxygen metabolism after cardiac surgery because of oxygen debts that occurred during cardiopulmonary bypass. A prospective study was designed to determine oxygen consumption and carbon dioxide production using an indirect calorimeter in 45 adult patients who underwent hypothermic cardiopulmonary bypass. Inspiratory and expiratory gases were analyzed and the respiratory exchange ratio (carbon dioxide production/ oxygen consumption) was obtained every 6 hours up to 24 hours after surgery. The respiratory exchange ratio immediately following cardiopulmonary bypass was abnormally high then gradually decreased. The respiratory exchange ratio at 18 or 24 hours after surgery was significantly lower than the one on admission to the intensive care unit. Duration of cardiopulmonary bypass was the most significant parameter which correlated to the respiratory exchange ratio on admission to the intensive care unit (r = 0.82, p < 0.001). We conclude that the respiratory exchange ratio can be used to monitor systemic metabolism, especially during the recovery phase from metabolic abnormality following hypothermic cardiopulmonary bypass.
    Annals of thoracic and cardiovascular surgery: official journal of the Association of Thoracic and Cardiovascular Surgeons of Asia 06/1999; 5(3):150-5. · 0.69 Impact Factor
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    ABSTRACT: Arterial-venous carbon dioxide tension differences (Pv-aCO2) are known to increase during the resuscitation phase following several types of shock. We hypothesized that Pv-aCO2 increases immediately following hypothermic cardiopulmonary bypass (CPB) because of the metabolic impairments that occur during CPB. Fifty-six adult patients underwent hypothermic CPB for cardiac surgery. Arterial and mixed venous blood gases were analyzed every 6 hours for the first 24 hours following cardiac surgery. Immediately after surgery, the Pv-aCO2 was elevated (8.2 +/- 2.9 mmHg), but gradually returned to a normal range within 12 hours (6.2 +/- 3.2 mmHg, p < 0.001). Factors (X) which correlated significantly with the postoperative Pv-aCO2 (Y) included the minimum rectal temperature during CPB (Y= 27.3 - 0.664X, p = 0.011) and the duration of CPB (Y= 5.6 + 0.0172X, p = 0.047). The abnormally high Pv-aCO2 during the early postoperative period may be caused by metabolic impairments during hypothermic CPB. The recovery stage following open heart surgery is therefore similar to the resuscitation phase after shock.
    Annals of thoracic and cardiovascular surgery: official journal of the Association of Thoracic and Cardiovascular Surgeons of Asia 02/1999; 5(1):27-30. · 0.69 Impact Factor
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    ABSTRACT: Nitric monoxide (NO) is widely used in the medical treatment of acute respiratory distress syndrome (ARDS) and thus a safe and an effective production of NO is of interest to the medical community. The present work reports on: (1) the production of NO in dry air and in a mixture of O<sub>2</sub> (26%) and N<sub>2</sub>, and (2) the byproducts in the mixture of O<sub>2</sub> (26%) and N<sub>2</sub> subsequent to the application of a pulsed arc discharge. The byproducts which were measured using Fourier transform infrared spectroscopy (FTIR) in a mixture of O<sub>2</sub> (26%) and N<sub>2</sub> included NO, NO<sub>2 </sub>, N<sub>2</sub>O, H<sub>2</sub>O, CO, CO<sub>2</sub>, and CH<sub>4 </sub>. It is shown that in dry air, nitric oxide can be produced with the lowest ratio of NO<sub>2</sub>/NO<sub>X</sub> where NO<sub>X</sub>=NO+NO<sub>2</sub>. The generation of NO using dry air is economical and effective for medical applications
    Pulsed Power Conference, 1999. Digest of Technical Papers. 12th IEEE International; 02/1999
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    ABSTRACT: Data concerning inhaled nitric oxide (iNO) on pediatric ARDS is rare. We investigated the effects of iNO on pediatric ARDS in order to examine the ability to predict a response to iNO, the optimal concentration of iNO, the effects of < or = 1 ppm nitric oxide (NO), and the effect of iNO on PaCO2. ICU at Kumamoto (Japan) University Hospital. Seven children with ARDS. The initial responses to 16 ppm NO and the dose-response effects of 0.13 to 16 ppm NO were assessed. Sixteen ppm of iNO improved oxygenation in all seven children. The use of iNO significantly increased the ratio of arterial oxygen tension to the fraction of inspired oxygen (PaO2/FIO2). A correlation between the NO-induced increase in PaO2/FIO2 and the baseline PaO2/FIO2 was observed (r=0.93, p<0.01). Dose-response tests showed that the optimal concentration of iNO was < or = 4 ppm, improvements in PaO2/FIO2 could be observed with concentrations of < or = 1 ppm NO, and iNO induced a slight decrease in PaCO2. In children with ARDS, iNO frequently improves oxygenation and induces a slight decrease in PaCO2, with the baseline PaO2/FIO2 functioning as a predictor of all NO response. Improvements of PaO2 and PaCO2 were observed with concentrations of iNO of < or = 1 ppm, a level in which the risk of a toxic reaction in children is minimal. Effects on outcome need verification in larger controlled trials.
    Chest 10/1998; 114(3):827-33. DOI:10.1378/chest.114.3.827 · 7.13 Impact Factor
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    ABSTRACT: During nitric oxide (NO) inhalation therapy, toxicity may be produced by the reactive metabolite nitrogen dioxide (NO2). The purpose of the present study was to determine the NO2 concentration in a NO inhalation system used for respiratory failure in children at relatively low concentrations of NO (< 20 ppm). The production of NO2 in the NO inhalation system using the Servo Ventilator 900C connected to the test lung under each of 30 combinations of NO concentrations (0, 4, 8, 12, 16, and 19 ppm) and inspired oxygen (O2) concentrations (21, 40, 60, 80, and 100%). Pressure controlled ventilation was used with a respiratory rate of 20 breaths/min. NO and NO2 measurements were obtained on the inspiratory side of the Y-piece connected to the test lung. At a given NO level, increases in the concentration of inspired O2 resulted in increases in the concentration of NO2 produced, as did increases in the amount of NO at a given concentration of O2. The mean NO concentration at the inspiratory site of the Y-piece did not exceed 0.05 ppm (the limit of NO2 as an outdoor air pollutant in the United States) when the NO concentration did not exceed 8 ppm, regardless of the O2 concentration. NO inhalation therapy for children with severe respiratory failure using the Servo Ventilator 900C can be performed safely when the concentration of NO does not exceed 8 ppm.
    Acta paediatrica Japonica; Overseas edition 04/1997; 39(2):172-5.
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    ABSTRACT: A combination of veno-arterial bypass (VAB) and intraaortic balloon pumping (IABP) was applied to a 54-year-old male patient whose right heart function was severely damaged immediately following aortic valve replacement. A diagnosis of perioperative myocardial infarction was made with findings of severe hypokinesis of the right heart, new Q wave with ST elevation, and increased cardiac escaping enzyme. The VAB was maintained wih a pump flow rate of 2.0-2.5 L/min. The system was exchanged to the second one 42 hours after the surgery. According to repeated on/off testing, the VAB was successfully weaned on the 5th postoperative day followed by weaning IABP on the 6th postoperative day. This case report shows a recovery from isolated right heart failure by an immediate switching from a cardiopulmonary bypass to VAB and IABP.
    [Zasshi] [Journal]. Nihon Kyōbu Geka Gakkai 08/1996; 44(7):1027-32.

Publication Stats

94 Citations
13.33 Total Impact Points

Institutions

  • 1999–2009
    • Kumamoto University
      • • Graduate School of Science and Technology
      • • Department of Computer Science and Elecrical Engineering
      Kumamoto, Kumamoto Prefecture, Japan
  • 2007–2008
    • Shinshu University
      Shonai, Nagano, Japan
  • 2002
    • University of Windsor
      • Department of Electrical and Computer Engineering
      Windsor, Ontario, Canada