• Journal of Korean Society for Quality Management
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• v.35 no.4
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• pp.140-146
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• 2007

In this paper, we consider a periodic imperfect preventive maintenance(PM) policy in which the system's failure rate after each PM remains unchanged. The system undergoes only minimal repairs at failures between PMs. Exact mathematical formula of the expected cost rate per unit time is derived. Optimal number of PMs and optimal maintenance period are derived by minimizing the expected cost rate per unit time. A numerical example is provided to illustrate the proposed approach under Weibull lifetime distribution.

• Journal of Chest Surgery
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• v.24 no.2
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• pp.115-122
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• 1991

From April 1986 to December 1989, 25 infants under the age of 12 months with tetralogy of Fallot were operated on. Age ranged from 3 to 12 months[mean 8.9$\pm$4.9 months] and mean body weight was 7.8$\pm$ 2.6kg. All the patients were deeply cyanotic, 12 of them experienced anoxic spell. Transannular patch was laid down in 19 patients, in 7 of them monocuspid patch was utilized. Postrepair P RV/LV was measured at operation room in 17 patients[mean 0.48$\pm$0. 14]. Hospital mortality was 20Yo. Causes of deaths include right ventricular failure and low cardiac output. The mortality was closely related with patient`s age and body surface area at operation. Also higher mortality was noticed in patients having major associated anomaly or previous palliative operation, preoperative management with propranolol and transannular repair. 18 patients were followed up for 12 to 50 months with a mean follow-up time of 24 months after operation. There were no late deaths and late ventricular arrhythmia or congestive heart failure was not detected as yet. Redo operation was performed in one case because of residual pulmonic stenosis. Considering several advantages of early primary repair, primary repair of symptomatic infants with tetralogy of Fallot should be encouraged despite somewhat high mortality rate as yet and better results could be anticipated along with improvement of myocardial protection method and postoperative care.

• Journal of Chest Surgery
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• v.23 no.3
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• pp.438-451
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• 1990

Pneumatic total artificial heart[TAH] has been clinically applied for the purpose of permanent or temporary use followed by cardiac transplantation in the patients with end stage heart diseases. In spite of the good durability of the pneumatic TAH, thrombus formation, bleeding and infection resulted in death. The Tomasu heart, which is a type of pneumatic TAH, was used in this study. This model is a modified Jarvik heart and consists of atrial cuffs, outflow vascular grafts and thin-layer seamless diaphragm type of ventricles. Cardiac outputs of the left artificial heart were measured by Donovan`s mock circulation under variable conditions of driving parameters, and an experimental artificial heart implantation was performed in 4 calves to observe the changes of hemodynamic parameters in early postoperative period and hematologic and bio-chemical changes in a long-term survival case. In the mock circulation test, cardiac output of the heart was increased with the increase of the left atrial pressure and left driving pressure. Maximum cardiac output was obtained at the heart rate of 120 to 130/min and percent systole of 40 to 45Zo under the condition of a constant left driving pressure of 180mmHg and left atrial pressure of 10mmHg. During the first 24 hours of TAH pumping, driving pressure ranged from 178$\pm$5mmHg to 187$\pm$8mmHg for the left heart and from 58$\pm$6mmHg to 78$\pm$28mmHg for the right heart. The Mean arterial pressure significantly increased between 2 and 8 hours after the start of pumping. The survival time ranged from 27 hours to 46 days. The causes of death were respiratory failure in 2 cases, mechanical valve failure in one, and left ventricular outflow obstruction due to thrombus in a 46-day survival case. This study demonstrated that Tomasu artificial heart operated effectively during the first 24 hours of artificial heart pumping, but thrombus formation around the valve holding area was the main problem in long-term survival case.

• Clinical and Experimental Reproductive Medicine
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• v.44 no.2
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• pp.96-104
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• 2017

Objective: This study aimed to compare the clinical outcomes between in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in sibling oocytes. Additionally, we evaluated whether the implementation of split insemination contributed to an increase in the number of ICSI procedures. Methods: A total of 571 cycles in 555 couples undergoing split insemination cycles were included in this study. Among them, 512 cycles (89.7%) were a couple's first IVF cycle. The patients were under 40 years of age and at least 10 oocytes were retrieved in all cycles. Sibling oocytes were randomly allocated to IVF or ICSI. Results: Total fertilization failure was significantly more common in IVF cycles than in ICSI cycles (4.0% vs. 1.4%, p<0.05), but the low fertilization rate among retrieved oocytes (as defined by fertilization rates greater than 0% but < 30%) was significantly higher in ICSI cycles than in IVF cycles (17.2% vs. 11.4%, p<0.05). The fertilization rate of ICSI among injected oocytes was significantly higher than for IVF ($72.3%{\pm}24.3%$ vs. $59.2%{\pm}25.9%$, p<0.001), but the fertilization rate among retrieved oocytes was significantly higher in IVF than in ICSI ($59.2%{\pm}25.9%$ vs. $52.1%{\pm}22.5%$, p<0.001). Embryo quality before embryo transfer was not different between IVF and ICSI. Although the sperm parameters were not different between the first cycle and the second cycle, split insemination or ICSI was performed in 18 of the 95 cycles in which a second IVF cycle was performed. Conclusion: The clinical outcomes did not differ between IVF and ICSI in split insemination cycles. Split insemination can decrease the risk of total fertilization failure. However, unnecessary ICSI is carried out in most split insemination cycles and the use of split insemination might make ICSI more common.

• Childhood Kidney Diseases
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• v.12 no.1
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• pp.30-37
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• 2008

Purpose: The present study is an investigation of the progression and prognosis of acute intrinsic renal failure in neonates and children with a diagnosis of acute renal failure or other diseases on admission. Methods: This research is based on a retrospective analysis conducted on 59 patients(male: female=2.2:1) diagnosed with acute intrinsic renal failure between January 2000 and June 2006 at Busan Paik Hospital. The clinical diagnostic criteria of acute renal failure used was serum creatinine <1.2 mg/dL, oliguria with urine output$\leq$0.5 mL/kg/hr and anuria with urine output <50 mL per day. Results: Among those placed under investigation, 7 patients were neonates, 10 patients were 2 months-2 years old, 12 patients were 3-6 years old, 21 patients were 7-12 years old and 9 patients were 13-16 years old. It took 3.1${\pm}$2.8 days on average until the diagnosis was made. The urine output distribution was 21 persons for the oliguria group, and 36 persons for the non-oliguria group, and 2 persons for the anuria group. For the underlying causes, 30 persons were classified in the primary renal disease group, 14 persons in the infection group, 9 persons in the malignancy group, and 6 persons were categorized in another group. As for age distribution, the infected group was predominantly neonates, whereas the dominant age ranges for the primary renal disease and infection categories were 2 months to 2 years old. Also, the primary renal disease was dominant among older children, aged 3 and up. No difference was detected according to seasonal prevalence. However, there was a high morbidity rate among hemolytic uremic syndrome diagnosed in the summer. Peritoneal dialysis was used to treat 4 patients. It took 10.0${\pm}$6.7 days until the patients improved. 18 patients died. The non-oliguria group's mortality rate was lower than other groups. There was a high mortality rate in the neonates and malignancy group. Conclusion: Acute renal failure in childhood seems to take a better clinical course than in adulthood when there is an early diagnosis and proper treatment of underlying diseases.

• Journal of Chest Surgery
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• v.30 no.4
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• pp.373-377
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• 1997

Between January, 1991 and May 1995, mitral valve repair was undertaken on 32 patients under 15 years for congenital mitral regurgitation. Mean age was 24.0$\pm$26.1 months(range 3 months to 15 years), 16 patients were male and 16 patients were female associated cardiac anomalies were found in 26 patients (81%), and ventricular septal defects were noted in 18 patients(56%). In regards to pathologic findings, there were annular dilatation(n:7), leaflet prolapse(n=18), cleft leaflet(n=5) and restricted valve motion (n=2). The method of repair consisted of annuloplasty(Modif ed Devega type) in 14, repair of redundunt leaflet in 6, closure of cleft in 5, triangular resection in 2 and splitting of papillary muscle in one. There was no operative mortality and two late deaths occurred as a result of heart failure and sepsis. Tro patients required replacement of the mitral valve after 3 months and 7 months respectivehy because of recurrent mitral regurgitation. Actuarial survival was 92.5% at 46 months and actuarial freedom from reoperation was 95% at 12 months and 92.5% at 46 months. Actuarial freedom from valve repair failure was 68% at 12 months and 61.8% at 46 months. Although valve repair failure rate was high, we believe that mitral valve repair should be of rcrred to children because of low mortality and low reoperation rate.

• Journal of Chest Surgery
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• v.31 no.6
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• pp.591-597
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• 1998

Background: The aim of the current study was to analyze the early and intermediate-term performance of aortic valve replacement. Material and Method: Between January 1986 and January 1996, records of 61 consecutive patients who had received aortic valve replacement were reviewed. 38 were male and 23 were female patients, ranging from 10 to 71 years of age(mean: 40.5${\pm}$11.2). Results: The early death rate was 4.9%(3/61). A thorough follow-up rate of 93.1% was accomplished in these 58 patients who left the hospital(mean: 51.5${\pm}$32.0 patient-months) under the assistance of the same operator. Three of these patients who left the hospital died. The late death rate was 5.2%(3/58). Five patients experienced anticoagulant-related hemorrhage(all were minor). Three patients had thromboembolic episodes. There was no clinical evidence of hemolysis and structural failure of valves used. Of those patients who survived, the NYHA functional class improved significantly. Linearized rate were 1.58%/patient-year and 2.0%/patient-year respectively for thromboembolism and anticoagulant-related hemorrhage. The 10 year actuarial survival rate was 83.6%. Conclusion: This early and intermediate-term follow-up suggests that the mechanical valve is a reliable and durable prosthesis with good hemodynamic function and low rate of prosthesis-related complication.

• Tuberculosis and Respiratory Diseases
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• v.46 no.3
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• pp.350-362
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• 1999

Background: Acute Respiratory failure which is developed after extubation in the weaning process from mechanical ventilation is an important cause of weaning failure. Once it was developed, endotracheal reintubation has been done for respiratory support. Noninvasive Positive Pressure Ventilation (NIPPV) has been used in the management of acute or chronic respiratory failure, as an alternative to endotracheal intubation, using via nasal or facial mask. In this study, we evaluated the usefulness of NIPPV as an alternative method of reintubation in patients who developed acute respiratory failure after extubation. Method: We retrospectively analyzed thirty one patients(eighteen males and thirteen females, mean ages $63\pm13.2$ years) who were developed acute respiratory failure within forty eight hours after extubation, or were extubated unintentionally at medical intensive care unit(MICU) of Asan Medical Center. NIPPV was applied to the patients. Ventilatory mode of NIPPV, level of ventilatory support and inspiratory oxygen concentration were adjusted according to the patient condition and results of blood gas analysis by the attending doctors at MICU. NIPPV was completely weaned when the patients maintained stable clinical condition under 8 $cmH_2O$ of pressure support level. Weaning success was defined as maintenance of stable spontaneous breathing more than forty eight hours after discontinuation of NIPPV. Respiratory rate, heart rate, arterial blood gas analysis, level of pressure support, and level of PEEP were monitored just before extubation, at thirty minutes, six hours, twenty four hours after initiation of NIPPV. They were also measured at just before weaning from NIPPV in success group, and just before reintubation in failure group. Results: NIPPV was successfully applied to thirty-one patients of thirty-two trials and one patient could not tolerated NIPPV longer than thirty minutes. Endotracheal reintubation was successfully obviated in fourteen patients (45%) among them. There was no difference in age, sex, APACHE III score on admission at MICU, duration of intubation, interval from extubation to initiation of NIPPV, baseline heart rate, respiratory rate, arterial blood gas, and $PaO_2/FiO_2$ between the success and the failure group. Heart rate and respiration rate were significantly decreased with increase $SaO_2$ after thirty minutes of NIPPV in both groups(p<0.05). However, in the patients of failure group, heart rate and respiratory rate were increased again with decrease in $SaO_2$ leading to endotracheal reintubation. The success rate of NIPPV treatment was significantly higher in the patients with COPD compared to other diseases(62% vs 39%) (p=0.007). The causes of failure were deterioration of arterial blood gas without aggravation of underlying disease(n=9), aggravation of undelying disease(n=5), mask intolerance(n=2), and retained airway secretion(n=l). Conclusion: NIPPV would be a useful therapeutic alternative which can avoid reintubation in patient who developed acute respiratory failure after extubation.

• Current Research on Agriculture and Life Sciences
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• v.4
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• pp.109-113
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• 1986

In order to study the changes of pregnancy rates according to the factors, age, season, repeated utilization, synchrony, of recipients (29 holstein heifers, one Korean native heifer and 3 holstein cows) were transfered one embryo (from morulae stage to advanced blastocyst) to each, and the results are as follows ; 1. The effect of age of recipient on pregnancy rate in cows and 18-24months of aged group are 100% and 78%, respectively. Under 14months of aged group recorded the worst, 67%. 2. In winter (Nov.-Jan.) and spring (Feb.-Apr.), the pregnancy rate were better than others 100%, 83%, respectively. In the autumn (Aug.-Oct.), it was only 50%, the worst. 3. Among 31 recipients which were utilized at the first, 25 were pregnanted (80.7%), but in the second utilization after the failure of the first transfering, 2 heifers, none of pregnancy was obtained. 4. Pregnancy rates related to synchronization of estrus between donor and recipients are;-(before donor)12hrs. (100%), -6hrs. (86%), +( after donor)6hrs. (67%), + 12hrs. (79%), and +over 12hrs. (50%), respectively. 5. Differences in the pregnancy rate of the recipients +over 12hrs. were significantly large, so in order to ger good pregnancy rate in embryo transfer, the differences of the synchronization must be reduced inner ${\pm}12hrs$. In general, recipients estrus before donor showed better pregnancy rate than estrus after donor.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.11
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• pp.6637-6641
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• 2013

Background: To evaluate the results of various types of radiofrequency ablation (RFA) treatment of renal tumors in patients with excessive anesthetic and surgical risk. Materials and Methods: Data for RFA performed in in high risk patients were retrospectively evaluated. Other RFA applications in patients with no anesthetic and/or surgical risk were excluded. RFA was by ultrasound or CT guided percutaneous (USG/CT-PRFA) and retroperitoneally or transperitoneally laparoscopic (R/T-LRFA) techniques under general or local anethesia. Follow-up data of enhanced CT or MRI after 1, 3 and 6 months were analysed for twelve RFA applications. Results: The RFA applications included 4 (40%) left-sided, 5 (50%) right-sided and 1 (10%) bilaterally RFA (simultaneously 1 right and 2 left). The localizations of tumors were 2 (16.6%) upper, 5 (41.6%) mid and 5 (41.6%) lower pole. The RFA applications included 9 (75%) USG-PRFA, 1 (8.3%) CT-PRFA, 1 (8.3%) T-LRFA and 1 (8.3%) R-LRFA. The mean age was $65.3{\pm}8.5$ (52-76) years. The mean tumor size was $29.6{\pm}6.08$ (15-40) mm. No complications related to the RFA were encountered in any of the cases. Failure (residual tumour) was determined in 8.3% (1/12) of USG-RFA application. The success rate was thus 91.7% (11/12). Other 1st, 3rd and 6th months follow-up data revealed no residua and recurrence. Conclusions: RFA application appears to be safe as a less invasive and effective treatment modality in selected cases of small renal tumors in individuals with excessive anesthetic and also surgical risk.