• Title/Summary/Keyword: Method comparison

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20 Years Surgical Experiences for Ebstein's Anomaly (엡스타인 기형의 20년 수술 치험)

  • Lee, Sak;Park, Han-Ki;Lee, Chang-Young;Chang, Byung-Chul;Park, Young-Hwan
    • Journal of Chest Surgery
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    • v.40 no.4 s.273
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    • pp.280-287
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    • 2007
  • Background: We retrospectively evaluated the clinical results of surgically managing patients with Ebstein's anomaly. Material and Method: Between Feb. f 984 and June 2006, 50 patients who underwent surgical treatment for Ebstein's anomaly at Yonsei Cardiovascular Center were retrospectively reviewed. The mean age of the patients was 26.9 years and 19 patients were male, Associated anomalies included atrial septal defect (33), patent ductus arteriosus (2), ventricular septal defect (1), and pulmonary stenosis (4), and 90%, (45/50) of the patients had more than a moderate degree of tricuspid regurgitation. Carpentier type A was present in 6 patients, type B in 26, type C in 14 and type D in 4. Ten patients were associated with WPW syndrome. Conservative surgery was possible in 31 patients (tricuspid annuloplasty, plication of the atrialized RV), Fontan's operation was peformed in 4 patients, tricuspid valve replacement was done in 12 and palliative surgery was done in 2 patients. Thirteen patients were associated with hi-directional cavopulmonary shunt (BCPS: one and a half ventricular repairs): 10 patients with WPW syndrome and 4 patients with atrial fibrillation underwent concomitant ablation. Result: The postoperative median NYHA functional class $(3{\rightarrow}1)$ and the mean cardio-thoracic ratio $(0.65{\rightarrow}0.59)$ were decreased significantly (p<0.001, p=0.014). The mean oxygen saturation $(86.6{\rightarrow}94.1%)$, and median TR grade $(4{\rightarrow}1)$ were also significantly improved (p=0.004, p<0.001). For comparison of BCPS and conservative surgery, the preoperative right ventricular pressure (33.0 vs. 41.3 mmHg), the ICU stay (2.80 vs. 1.89 days), the hospital say (10.6 vs. 16.8 days), and the left ventricular ejection fraction (64.3 vs. 72.8%) were statistically different. Postoperative mortality occurred in 3 patients (6%) due to biventricular failure in 2 patients and sepsis in the other patient. The mean follow up duration was 101.5 months, and one patient died of Fontan failure and 6 patients required reoperation (bioprosthetic degenerative change (2) and Fontan conversion (4)). The overall survival rate at 10 years was 90.2%, the freedom from reoperation rate and rate of cardiac related events were 78.9% and 49.2%, respectively. Conclusion: Surgical management of Ebstein's anomaly can be performed safely, and the associated BCPS may be helpful for high-risk patients. Adequate application of surgical management may increase the long-term survival with a reduced rate of reoperation.

The Relationship Between DEA Model-based Eco-Efficiency and Economic Performance (DEA 모형 기반의 에코효율성과 경제적 성과의 연관성)

  • Kim, Myoung-Jong
    • Journal of Environmental Policy
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    • v.13 no.4
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    • pp.3-49
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    • 2014
  • Growing interest of stakeholders on corporate responsibilities for environment and tightening environmental regulations are highlighting the importance of environmental management more than ever. However, companies' awareness of the importance of environment is still falling behind, and related academic works have not shown consistent conclusions on the relationship between environmental performance and economic performance. One of the reasons is different ways of measuring these two performances. The evaluation scope of economic performance is relatively narrow and the performance can be measured by a unified unit such as price, while the scope of environmental performance is diverse and a wide range of units are used for measuring environmental performances instead of using a single unified unit. Therefore, the results of works can be different depending on the performance indicators selected. In order to resolve this problem, generalized and standardized performance indicators should be developed. In particular, the performance indicators should be able to cover the concepts of both environmental and economic performances because the recent idea of environmental management has expanded to encompass the concept of sustainability. Another reason is that most of the current researches tend to focus on the motive of environmental investments and environmental performance, and do not offer a guideline for an effective implementation strategy for environmental management. For example, a process improvement strategy or a market discrimination strategy can be deployed through comparing the environment competitiveness among the companies in the same or similar industries, so that a virtuous cyclical relationship between environmental and economic performances can be secured. A novel method for measuring eco-efficiency by utilizing Data Envelopment Analysis (DEA), which is able to combine multiple environmental and economic performances, is proposed in this report. Based on the eco-efficiencies, the environmental competitiveness is analyzed and the optimal combination of inputs and outputs are recommended for improving the eco-efficiencies of inefficient firms. Furthermore, the panel analysis is applied to the causal relationship between eco-efficiency and economic performance, and the pooled regression model is used to investigate the relationship between eco-efficiency and economic performance. The four-year eco-efficiencies between 2010 and 2013 of 23 companies are obtained from the DEA analysis; a comparison of efficiencies among 23 companies is carried out in terms of technical efficiency(TE), pure technical efficiency(PTE) and scale efficiency(SE), and then a set of recommendations for optimal combination of inputs and outputs are suggested for the inefficient companies. Furthermore, the experimental results with the panel analysis have demonstrated the causality from eco-efficiency to economic performance. The results of the pooled regression have shown that eco-efficiency positively affect financial perform ances(ROA and ROS) of the companies, as well as firm values(Tobin Q, stock price, and stock returns). This report proposes a novel approach for generating standardized performance indicators obtained from multiple environmental and economic performances, so that it is able to enhance the generality of relevant researches and provide a deep insight into the sustainability of environmental management. Furthermore, using efficiency indicators obtained from the DEA model, the cause of change in eco-efficiency can be investigated and an effective strategy for environmental management can be suggested. Finally, this report can be a motive for environmental management by providing empirical evidence that environmental investments can improve economic performance.

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Low Dose Cisplatin as a Radiation Sensitizer in Management of Locally Advanced Scluamous Cell Carcinoma of the Uterine Cervix : Evaluation of Acute Toxicity and Early Response (국소 진행된 자궁경부암의 방사선치료와 저용량 cisplatin 항암요법 동시치료시 급성독성 밀 초기반응 평가)

  • Kim Hunjung;Cho Young Kap;Kim Chulsu;Kim Woo Chul;Lee Sukho;Loh J K
    • Radiation Oncology Journal
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    • v.17 no.2
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    • pp.113-119
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    • 1999
  • Purpose : To evaluate possible acute toxicity and early response of concurrent radiation therapy and low dose daily cisplatin as a radiosensitizer in patients with locally advanced uterine cervical carcinomas. Materials and Method : From December 1996 to January 1999, 38 previously untreated Patients with locally advanced squamous cell carcinoma of the uterine cervix (from stage IIB to stage IIIB) were treated at Inha University Hospital. All patients underwent standard pretreatment staging Procedures after the initial evaluation by gynecologists and radiation oncologists. Sixteen Patients with huge cervical mass (>4 cm) were submitted to the group treated with concurrent radiation therapy and low dose daily cisplatin while the remainder was treated with radiation therapy alone. Radiation therapy consisted of 4500 cGy external beam irradiation to whole pelvis (midline block after 3000 cGy), 900$\~$1000 cGy boost to involved parametrium, and high dose-rate intracavitary brachytherapy (a total dose of 3000$\~$3500 cGy/500 cGy per fraction to point A, twice per week). In the group treated with low dose cisplatin concurrently, 10 mg of daily intravenous cisplatin was given from the 1st day of radiation therapy to the 20th day of radiation therapy. Acute toxicity was measured according to expanded common toxicity criteria of the NCI (C) Clinical Trials. Early response data were analyzed at minimum 4 weeks' follow-up after completion of the treatment protocol. Results: Hematolgic toxici쇼 was more prominent in patients treated with radiation therapy and cisplatin. Six of 16 patients (37.5$\~$) treated with radiation therapy and cisplatin and one of 22 patients (4.5$\~$) treated with radiation therapy alone experienced grade 3 leukopenia. In Fisher's exact test, there was statistically significant difference between two groups regarding leukopenia (P=0.030). There was no apparent difference in the frequency of gastrointestinal and genitourinary toxicity between two groups (P=0.066). Three of 16 patients (18.7$\~$) treated with radiation therapy and cisplatin and two of 22 patients (9.1$\~$) treated with radiation therapy alone experienced more than 5 kg weight loss during the treatment. There was no statistically significant difference on weight loss between two groups (P=0.63). Two patients on each group were not evaluable for the early response because of incomplete treatment. The complete response rate at four weeks' follow-up was 80$\~$(16/20) for the radiation therapy alone group and 78$\~$ (11/14) for the radiation therapy and cisplatin group. There was no statistically significant difference in early response between two treatment groups (P=0.126). Conclusion : This study led to the conclusion that the hematologic toxicity from the treatment with concurrent radiation therapy and low dose daily cisplatin seems to be more prominent than that from the treatment of radiation therapy alone. There was no grade 4 hematologic toxicity or mortality in both groups. The hematologic toxicity in both treatment groups seems to be well managable modically. Since the risk factors were not balanced between two treatment groups, the direct comparison of early response of both groups was not possible. However, preliminary results regarding early response for patients with bulky cervical tumor mass treated with radiation therapy and low dose daily cisplatin was encouraging. Longer follow-up is necessary to evaluate the survival data. A phase III study is needed to evaluate the efficacy of concurrent daily low dose cisplatin with radiation therapy in bulky cervical cancer.

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A Retrospective Study of the Radiotherapy Care Patterns for Patients with Laryngeal Cancer and Comparison of Different Korean Hospitals Treated from 1998 through 1999 (한국인 후두암 환자의 방사선치료 과정 및 내용에 관한 분석 (1998~1999년도))

  • Chung, Woong-Ki;Kim, Il-Han;Yoon, Mee-Sun;Ahn, Sung-Ja;Nam, Taek-Keun;Song, Ju-Young;Chung, Jae-Uk;Nah, Byung-Sik;Lee, Joon-Kyoo;Wu, Hong-Gyun;Lee, Chang-Geol;Lee, Sang-Wook;Park, Won;Ahn, Yong-Chan;Kang, Ki-Moon;Kim, Jung-Soo;Oh, Yoon-Kyeong;Cho, Moon-June;Park, Woo-Yoon;Kim, Jin-Hee;Choi, Doo-Ho;Yun, Hyong-Geun;Kim, Woo-Cheol;Yang, Dae-Sik;Sohn, Seung-Chang;Suh, Hyun-Suk;Ahn, Ki-Jung;Chun, Mi-Son;Lee, Kyu-Chan;Choi, Young-Min;Jeung, Tae-Sik;Kang, Jin-Oh
    • Radiation Oncology Journal
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    • v.27 no.4
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    • pp.201-209
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    • 2009
  • Purpose: To investigate the care patterns for radiation therapy and to determine inter-hospital differences for patients with laryngeal carcinoma in Korea. Materials and Methods: A total of 237 cases of laryngeal carcinoma (glottis, 144; supraglottis, 93) assembled from 23 hospitals, who underwent irradiation in the year of 1998 and 1999, were retrospectively analyzed to investigate inter-hospital differences with respect to radiotherapy treatment. We grouped the 23 hospitals based on the number of new patients annually irradiated in 1998; and designated them as group A (${\geq}$900 patients), group B (${\geq}$400 patients and <900 patients), and group C (<400 patients). Results: The median age of the 237 patients was 62 years (range, 25 to 88 years), of which 216 were male and 21 were female. The clinical stages were distributed as follows: for glottis cancer, I; 61.8%, II; 21.5%, III; 4.2%, IVa; 11.1%, IVb; 1.4%, and in supraglottic cancer, I; 4.3%, II; 19.4%, III; 28.0%, IVa; 43.0%, IVb; 5.4%, respectively. Some differences were observed among the 3 groups with respect to the dose calculation method, radiation energy, field arrangement, and use of an immobilization device. No significant difference among 3 hospital groups was observed with respect to treatment modality, irradiation volume, and median total dose delivered to the primary site. Conclusion: This study revealed that radiotherapy process and patterns of care are relatively uniform in laryngeal cancer patients in Korean hospitals, and we hope this nationwide data can be used as a basis for the standardization of radiotherapy for the treatment of laryngeal cancer.

Biodistribution of 3-[$^{131}I$]iodo-O-methyl-L-${\alpha}$-methyltyrosine in Tumor Bearing Rats: A Comparison Study with L-3-[$^{131}I$]iodo-${\alpha}$-methyltyrosine (종양 이식 백서에서 3-[$^{131}I$iodo-O-methyl-L-${\alpha}$-methyltyrosine의 체내 동태 연구: L-3-[$^{131}I$iodo-${\alpha}$-methyltyrosine와 비교)

  • Choi, Chang-Woon;Yang, Seung-Dae;Woo, Kwang-Sun;Chung, Wee-Sup;Lim, Soo-Jung;Suh, Yong-Sup;Chun, Kwon-Soo;Ahn, Soon-Hyuk;Lee, Jong-Doo;Hong, Sung-Woon;Lim, Sang-Moo
    • The Korean Journal of Nuclear Medicine
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    • v.32 no.3
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    • pp.290-297
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    • 1998
  • Purpose : The aim of this study was to evaluate the feasibility of 3-[$^{131}I$]iodo-O-methyl-L-${\alpha}$-methyltyrosine ([$^{131}I$]OMIMT) as an agent for tumor image. Materials and Methods : After synthesis of 4-O-methyl-L-${\alpha}$-methyltyrosine (OMAMT), OMAMT was labeled with [$^{131}I$] using Iodogen method. In vitro cellular uptake study was performed using 9 L gliosarcoma cells at various time points upto 4 hr. The biodistribution (five rats implanted with the 9 L gliosar-coma cells per group) was evaluated at 30 min, 2 hr, 24 hr after iv injection of 3.7 MBq [$^{131}I$]OMIMT or L-3-[$^{131}I$]iodo-${\alpha}$-methyltyrosine [$^{131}I$]IMT). Gamma camera images were obtained at 30 min, 2 hr and 24 hr. Results: [$^{131}I$]OMIMT uptake was 3.3 times and 2.5 times higher than [$^{131}I$]IMT uptake at 30 min and 60 min, respectively and same after 2 hr in in vitro study using 9L gliosarcoma cells. Maximum accumulation in tumor occurred at 30 min for both [$^{131}I$]OMIMT and [$^{131}I$]IMT in tumor bearing rats. The tumor uptake of [$^{131}I$]OMIMT was significantly higher than that of [$^{131}I$]IMT at early time point studied ($3.74{\pm}0.48$ vs $0.38{\pm}0.17%$ ID/g at 30 min and $2.40{\pm}0.17$ vs $0.24{\pm}0.03%$ ID/g at 2 hr, respectively, p<0.01). However, the tumor uptake of both radiolabels were not significantly different at 24 hr ($0.04{\pm}0.01$ vs $0.05{\pm}0.01%$ ID/g). Tumor was visualized as early as at 30 min in gamma camera images. Conclusion: These data suggested that [$^{131}I$]OMIMT might be a useful tumor imaging agent and has more advantage for the tumor imaging compared to [$^{131}I$]IMT

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The study of food habit and degree of depression in nursing home and privite home living elderly (시설노인과 재가노인의 식습관과 정신건강 상태에 관한 실태조사)

  • Han, Myung-Joo;Koo, Sung-Ja;Lee, Young-Soon
    • Journal of the Korean Society of Food Culture
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    • v.13 no.5
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    • pp.475-486
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    • 1998
  • The dietary habit, health condition and the cognition concerning the health food have been surveyed with the help of the 151 old people living in In-Cheon and Seoul. In this study, the old are classified as an institution for the aged and the old in their own home. The preference and mental health condition influenced on dietary habits have been surveyed as wall. Their dietary habits such s three meals a day and a regular meal time have show) that they have generally good eating habits. Psychologically, the old in an institution for the aged think their health condition is not so good in comparison with the old in their own home. The old in their own home have good condition in that they can go up the stairs, exercise often and walk relatively well. Moreover, men's health condition is better than women. The old generally like meats(especially beef) and prefer sesame oil, perilla oil, soy been oil to Western oil. They like sweat flavor the most and hot, salty taste in order. Thier favorite cooking method is a pot stew, soup and season. The difference between dietary habit and mental health based on an academic career, an allowance and a residential condition shows that the old who live alon have relatively terrible eating habit and the more learned, the better. The more pocket money they have, the better dietary habits they have. The old feel glommy in general and the old in an institution are more depressed and it is statistically significant.

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Study the Analysis of Comparison with AROI and MROI Mode in Gated Cardiac Blood Pool Scan (게이트심장혈액풀 스캔에서 자동 관심영역 설정과 수동 관심영역 설정 모드의 비교 분석에 관한 고찰)

  • Kim, Jung-Yul;Kang, Chun-Koo;Kim, Yung-Jae;Park, Hoon-Hee;Kim, Jae-Sam;Lee, Chang-Ho
    • The Korean Journal of Nuclear Medicine Technology
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    • v.12 no.3
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    • pp.222-228
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    • 2008
  • Purpose: The objectives of this study were to compare the left ventricle ejection fraction (LVEF) from gated cardiac blood pool scan (GCBP) for analysis auto-drawing region of interest mode (AROI) and manual-drawing region of interest mode (MROI), respectively. To evaluation the relationships between values produced by both ROI modes. Materials and Methods: Gated cardiac blood pool scan using in vivo method Tc-99m Red Blood Cell were performed for 33 patients (mean age: $53.2{\pm}13.2\;y$) with objective of chemotherapy using single head gamma camera (ADAC Laboratories, Milpitas, CA). Left ventricular ejection fraction was automatically and manually measured, respectively. Results: There was significant difference statistically between AROI and MROI ($LVEF^{AROI}$: $71.4{\pm}12.4%$ vs. $LVEF^{MROI}$: $65.8{\pm}5.9%$, p=0.003). Intra-observer agreements in AROI was higher than MROI ($\gamma^{AROI}=0.964$, Cronbach's $\alpha^{AROI}=0.986$ vs. $\gamma^{MROI}=0.793$, Cronbach's $\alpha^{MROI}=0.911$), either. Additionally, there was no significant difference statistically at best septal view (${\Delta}LVEF^{BSV}=0.7{\pm}2.3%$, p=0.233), however statistically significant difference was found at badly separated septal view (${\Delta}LVEF=10.9{\pm}11.4%$, p=0.001). Moreover, Intra-observer agreements in best septal view was higher than badly separated septal view ($\gamma^{BSV}=0.939$, Cronbach's $\alpha^{BSV}=0.978$; $\gamma=0.948$, Cronbach's $\alpha=0.981$ at AROI, $\gamma^{BSV}=0.836$, Cronbach's $\alpha^{BSV}=0.936$; $\gamma=0.748$, Cronbach's $\alpha=0.888$ at MROI). Conclusion: When best septal view was acquired, LVEF by AROI and MROI indicated not different. Comparing Intra-observer agreements with AROI and MROI, the AROI tended to show higher. Therefore, it is considered that the AROI than MROI is valuable in reproducibility and objective when ROI analysis by acquire left ventricular of best septal view.

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A Comparison of Dietary Behaviors According to Gender and Obesity Status of Middle School Students in Jeonju (전주지역 중학생의 성별 및 비만판정에 따른 식행동 비교 연구)

  • Sung, Sun-Hwa;Yu, Ok-Kyeong;Son, Hee-Sook;Cha, Youn-Soo
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.36 no.8
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    • pp.995-1009
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    • 2007
  • The purpose of this study was to investigate the dietary habits, behaviors, and food consumption frequency according to gender and obesity level among middle school students in the Jeonju area. Subjects for the questionnaire were 450 middle school students (male 255, female 195) and were classified as either obese students (n=150 or non-obese students (n=299) by the obesity assessment method. The results were analyzed with SAS program (Version 9.1), and were as follows. 1. Dietary behaviors were significantly different in the rate of 'Skipping breakfast (p<0.05)', 'Duration of meal time (min) (p<0.05)' and 'Unbalanced diet (p<0.01)' between males and females. Dietary habits and behaviors also differed significantly for the rate of ‘Taste preferences (p<0.05)’, and 'Unbalanced diet (p<0.01)' between obese students and non-obese students. 2. Food consumption frequency per week was as follows. First, males were significantly higher than females in 'Instant noodle (p<0.05)', 'Milk (p<0.01)', and 'Soda pop (p<0.01)'; on the other hand females were significantly higher than males in 'Chocolate, Candy (p<0.01)'. Second, non-obese students were significantly higher than obese students in 'Instant noodle (p<0.05)', 'Hamburger, Pizza (p<0.05)', and 'Chocolate, Candy (p<001)'. Especially, non-obese male students were higher in 'Instant noodle (p<0.05)' and 'Hamburger, Pizza (p<0.05)'; non-obese female students were higher in 'Chocolate, Candy (p<0.01)'. In conclusion, an action program is needed to encourage healthful dietary behaviors, increased physical activity, and forming good lifelong habits.

The Diagnostic Yield and Complications of Percutaneous Needle Aspiration Biopsy for the Intrathoracic Lesions (경피적 폐생검의 진단성적 및 합병증)

  • Jang, Seung Hun;Kim, Cheal Hyeon;Koh, Won Jung;Yoo, Chul-Gyu;Kim, Young Whan;Han, Sung Koo;Shim, Young-Soo
    • Tuberculosis and Respiratory Diseases
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    • v.43 no.6
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    • pp.916-924
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    • 1996
  • Bacground : Percutaneous needle aspiration biopsy (PCNA) is one of the most frequently used diagnostic methcxJs for intrathoracic lesions. Previous studies have reponed wide range of diagnostic yield from 28 to 98%. However, diagnostic yield has been increased by accumulation of experience, improvement of needle and the image guiding systems. We analysed the results of PCNA performed for one year to evaluate the diagnostic yield, the rate and severity of complications and factors affecting the diagnostic yield. Method : 287 PCNAs undergone in 236 patients from January, 1994 to December, 1994 were analysed retrospectively. The intrathoracic lesions was targeted and aspirated with 21 - 23 G Chiba needle under fluoroscopic guiding system. Occasionally, 19 - 20 G Biopsy gun was used for core tissue specimen. The specimen was requested for microbiologic, cytologic and histopathologic examination in the case of obtained core tissue. Diagnostic yields and complication rate of benign and malignant lesions were ca1culaled based on patients' chans. The comparison for the diagnostic yields according to size and shape of the lesions was analysed with chi square test (p<0.05). Results : There are 19.9% of consolidative lesion and 80.1% of nodular or mass lesion, and the lesion is located at the right upper lobe in 26.3% of cases, the right middle lobe in 6.4%, the right lower lobe 21.2%, the left upper lobe in 16.8%, the left lower lobe in 10.6%, and mediastinum in 1.3%. The lesion distributed over 2 lobes is as many as 17.4% of cases. There are 74 patients with benign lesions, 142 patients with malignant lesions in final diagnosis and confirmative diagnosis was not made in 22 patients despite of all available diagnostic methods. 2 patients have lung cancer and pulmonary tuberculosis concomittantly. Experience with 236 patients showed that PCNA can diagnose benign lesions in 62.2% (42 patients) of patients with such lesions and malignant lesions in 82.4% (117 patients) of patients. For the patients in whom the first PCNA failed to make diagnosis, the procedure was repeated and the cumulative diagnostic yield was increased as 44.6%, 60.8%, 62.2% in benign lesions and as 73.4%, 81.7%, 82.4% in malignant lesions through serial PCNA. Thoracotomy was performed in 9 patients with benign lesions and in 43 patients with malignant lesions. PCNA and thoracotomy showed the same pathologic result in 44.4% (4 patients) of benign lesions and 58.1% (25 patients) of malignant lesions. Thoracotomy confirmed 4 patients with malignat lesions against benign result of PCNA and 2 patients with benign lesions against malignant result of PCNA. There are 1.0% (3 cases) of hemoptysis, 19.2% (55 cases) of blood tinged sputum, 12.5% (36 cases) of pneumothorax and 1.0% (3 cases) of fever through 287 times of PCNA. Hemoptysis and blood tinged sputum didn't need therapy. 8 cases of pneumothorax needed insertion of classical chest tube or pig-tail catheter. Fever subsided within 48 hours in all cases. There was no difference between size and shape of lesion with diagnostic yield. Conclusion: PCNA shows relatively high diagnostic yield and mild degree complications but the accuracy of histologic diagnosis has to be improved.

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The Effect of External PEEP on Work of Breathing in Patients with Auto-PEEP (Auto-PEEP이 존재하는 환자에서 호흡 일에 대한 External PEEP의 효과)

  • Chin, Jae-Yong;Lim, Chae-Man;Koh, Youn-Suck;Park, Pyung-Whan;Choi, Jong-Moo;Lee, Sang-Do;Kim, Woo-Sung;Kim, Dong-Soon;Kim, Won-Dong
    • Tuberculosis and Respiratory Diseases
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    • v.43 no.2
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    • pp.201-209
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    • 1996
  • Background : Auto-PEEP which develops when expiratory lung emptying is not finished until the beginning of next inspiration is frequently found in patients on mechanical ventilation. Its presence imposes increased risk of barotrauma and hypotension, as well as increased work of breathing (WOB) by adding inspiratory threshold load and/or adversely affecting to inspiratory trigger sensitivity. The aim of this study is to evaluate the relationship of auto-PEEP with WOB and to evaluate the effect of PEEP applied by ventilator (external PEEP) on WOB in patients with auto-PEEP. Method : 15 patients, who required mechanical ventilation for management of acute respiratory failure, were studied. First, the differences in WOB and other indices of respiratory mechanics were examined between 7 patients with auto-PEEP and 8 patients without auto-PEEP. Then, we applied the 3 cm $H_2O$ of external PEEP to patients with auto-PEEP and evaluated its effects on lung mechanics as well as WOB. Indices of respiratory mechanics including tidal volume ($V_T$), repiratory rate, minute ventilation ($V_E$), peak inspiratory flow rate (PIFR), peak expiratory flow rate (PEFR), peak inspiratory pressure (PIP), $T_I/T_{TOT}$, auto-PEEP, dynamic compliance of lung (Cdyn), expiratory airway resistance (RAWe), mean airway resistance (RAWm), $p_{0.1}$, work of breathing performed by patient (WOB), and pressure-time product (PTP) were obtained by CP-100 Pulmonary Monitor (Bicore, USA). The values were expressed as mean $\pm$ SEM (standard error of mean). Results : 1) Comparison of WOB and other indices of respiratory mechanics in patients with and without auto-PEEP : There was significant increase in WOB ($l.71{\pm}0.24$ vs $0.50{\pm}0.19\;J/L$, p=0.007), PTP ($317{\pm}70$ vs $98{\pm}36\;cm$ $H_2O{\cdot}sec/min$, p=0.023), RAWe ($35.6{\pm}5.7$ vs $18.2{\pm}2.3\;cm$ H2O/L/sec, p=0.023), RAWm ($28.8{\pm}2.5$ vs $11.9{\pm}2.0cm$ H2O/L/sec, p=0.001) and $P_{0.1}$ ($6.2{\pm}1.0$ vs 2.9+0.6 cm H2O, p=0.021) in patients with auto-PEEP compared to patients without auto-PEEP. The differences of other indices including $V_T$, PEFR, $V_E$ and $T_I/T_{TOT}$ showed no significance. 2) Effect of 3 cm $H_2O$ external PEEP on respiratory mechanics in patients with auto-PEEP : When 3 cm $H_2O$ of external PEEP was applied, there were significant decrease in WOB ($1.71{\pm}0.24$ vs $1.20{\pm}0.21\;J/L$, p=0.021) and PTP ($317{\pm}70$ vs $231{\pm}55\;cm$ $H_2O{\cdot}sec/min$, p=0.038). RAWm showed a tendency to decrease ($28.8{\pm}2.5$ vs $23.9{\pm}2.1\;cm$ $H_2O$, p=0.051). But PIP was increased with application of 3 cm $H_2O$ of external PEEP ($16{\pm}2$ vs $22{\pm}3\;cm$ $H_2O$, p=0.008). $V_T$, $V_E$, PEFR, $T_I/T_{TOT}$ and Cdyn did not change significantly. Conclusion : The presence of auto-PEEP in mechanically ventilated patients was accompanied with increased WOB performed by patient, and this WOB was decreased by 3 cm $H_2O$ of externally applied PEEP. But, with 3 cm $H_2O$ of external PEEP, increased PIP was noted, implying the importance of close monitoring of the airway pressure during application of external PEEP.

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