Yun Su Sim

Clinical Practice Guideline of Acute Respiratory Distress Syndrome

There is no well-stated practical guideline for mechanically ventilated patients with or without acute respiratory distress syndrome (ARDS). We generate strong (1) and weak (2) grade of recommendations based on high (A), moderate (B) and low (C) grade in the quality of evidence. In patients with ARDS, we recommend low tidal volume ventilation (1A) and prone position if it is not contraindicated (1B) to reduce their mortality. However, we did not support high-frequency oscillatory ventilation (1B) and inhaled nitric oxide (1A) as a standard treatment. We also suggest high positive end-expiratory pressure (2B), extracorporeal membrane oxygenation as a rescue therapy (2C), and neuromuscular blockage for 48 hours after starting mechanical ventilation (2B). The application of recruitment maneuver may reduce mortality (2B), however, the use of systemic steroids cannot reduce mortality (2B). In mechanically ventilated patients, we recommend light sedation (1B) and low tidal volume even without ARDS (1B) and suggest lung protective ventilation strategy during the operation to lower the incidence of lung complications including ARDS (2B). Early tracheostomy in mechanically ventilated patients can be performed only in limited patients (2A). In conclusion, of 12 recommendations, nine were in the management of ARDS, and three for mechanically ventilated patients.

Forced Expiratory Volume in One Second as a Prognostic Factor in Advanced Non-small Cell Lung Cancer

Introduction: Reduced lung function is an important risk factor for lung cancer and increases surgical risk in patients with operable stages of lung cancer. Nevertheless, there have been few studies to reveal association of lung function with mortality in patients with advanced lung cancer. The aim of this study was to investigate whether low forced expiratory volume in 1 second (FEV1) is an independent predictor of mortality in patients with advanced lung cancer. Methods: Data were retrospectively collected from patients with non-small cell lung cancer of stage IIIB or IV and available spirometry at diagnosis of lung cancer. They had the last follow-up consecutively between April 2003 and July 2009 in a tertiary referral hospital. Results: Among a total of 156 patients, 118 died as of July 2009. Their mean age was 65 years; 115 (74%) were men. Mean FEV1 was 1.91 liters (79% of predicted). Seventy-one patients (46%) had adenocarcinoma, and 48 (31%) had squamous cell carcinoma. In a multivariate analysis using Cox regression model, independent prognostic factors were FEV1 less than 50% of predicted (hazard ratio [HR] = 2.704, 95% confidence interval [CI]: 1.516–4.823, p = 0.001), chemotherapy (HR = 0.311, 95% CI: 0.192–0.503, p < 0.001), adenocarcinoma (HR = 0.459, 95% CI: 0.300–0.701, p < 0.001), body mass index (HR = 0.921, 95% CI: 0.870–0.975, p = 0.005), and the presence of malignant pleural effusion (HR = 1.673, 95% CI: 1.102–2.540, p = 0.016). Conclusions: Reduced FEV1 is strongly associated with mortality in advanced non-small cell lung cancer.

Prevalence and risk factors for reflux esophagitis in patients with chronic obstructive pulmonary disease

Background/Aims Gastroesophageal reflux disease is one of the most common causes of chronic cough and is a potential risk factor for the exacerbation of chronic obstructive pulmonary disease (COPD). The aim of this study was to investigate the prevalence and risk factors for reflux esophagitis (RE) in COPD patients. Methods From our hospital database, between September 2006 and April 2010, we searched for subjects who were 40 years old or older and had undergone both postbronchodilator spirometry and esophagogastroduodenoscopy (EGD). COPD was defined as having a ratio of forced expiratory volume in 1 second to forced vital capacity < 0.7 in postbronchodilator spirometry and no abnormality causing airway obstruction, except emphysematous changes, on a chest X-ray. The diagnosis of RE was based on a mucosal break surrounding the distal esophageal sphincter through EGD. Results In total, 253 patients with COPD were enrolled. The prevalence of RE in COPD was 30% (76/253). Multiple logistic regression analyses revealed that age (odds ratio [OR], 0.950; 95% confidence interval [CI], 0.918 to 0.983; p = 0.003), smoking pack-years (OR, 1.015; 95% CI, 1.004 to 1.025; p = 0.006), and inhaled anticholinergics (OR, 0.516; 95% CI, 0.271 to 0.982; p = 0.044) were independently associated with RE in COPD patients. Conclusions The prevalence of RE in our COPD patients was higher than that reported previously in the Korean general population. In COPD, smoking increased the risk of RE, whereas inhaled anticholinergics may be associated with a reduced risk of RE.

Association of Bone Mineral Density with Airway Obstruction and Emphysema

Background Airway obstruction and the extent of emphysema are reported to be responsible for reduced bone mineral density (BMD). Corresponding to different phenotypes of a pulmonary disease, different severity in extra pulmonary features may exist. We compared BMDs of subjects with or without airway obstruction and/or emphysema and investigated the relationships among BMD, the severity of airway obstruction, and the extent of emphysema. Methods Using a university hospital database, we reviewed patients over 40 years old who performed spirometry, computed tomography of chest, and measurement of BMD of the lumbar (L) spine. According to the presence or absence of airway obstruction and/or emphysema, four groups were classified. Results Among a total of 59 subjects, 33 (56%) had osteoporosis. The prevalence of osteoporosis in subjects with no airway obstruction and no emphysema, those with only emphysema, those with only airway obstruction, and those with both airway obstruction and emphysema were 42%, 57%, 64%, and 73%, respectively (p=0.047 by linear-by-linear association). The mean T-scores of BMD of L1 (p=0.032) and L1-4 spines were different among the four groups (p=0.034). Although the T-score of L1 BMD negatively correlated with the extent of emphysema (r=-0.275, p=0.035) and positively with each of body mass index (BMI) (r=0.520, p<0.001), forced expiratory volume in one second (FEV1) (r=0.330, p=0.011), FEV1/forced vital capacity (r=0.409, p=0.001), and forced expiratory flow at 25~75% of FVC (FEF25-75%) (r=0.438, p=0.0001), respectively, multiple linear regression analysis indicated that BMI (p<0.001) and FEF25-75% were predictive of BMD (p=0.012). Conclusion Low BMI and airway obstruction were strongly associated with reduced bone density rather than the extent of emphysema.

High blood neutrophil-lymphocyte ratio associated with poor outcomes in miliary tuberculosis

Background It is difficult to predict the prognosis of miliary tuberculosis (TB). We hypothesized that blood neutrophil-lymphocyte ratio (NLR) is an indicator of inflammatory status to reflect independent prognostic significance in patients with miliary TB. The aim of this study is to investigate the relationship between NLR and outcome in miliary TB. Methods We retrospectively collected data from patients diagnosed with miliary TB in a tertiary referral hospital between January 1995 and January 2016. Results A total of 96 patients were enrolled. Seventeen patients (18%) died during hospitalization due to miliary TB, and 9 (9%) died additionally during the 1-year follow-up period. Eighteen patients (19%) were diagnosed with acute respiratory distress syndrome (ARDS). In multiple logistic regression analyses, increased NLR was associated with ARDS [adjusted odds ratio, 1.15; 95% confidence interval (CI), 1.03-1.28]. By multivariate Cox regression analysis with adjustment of known prognostic factors including age, sex, body mass index, serum aspartate aminotransferase (AST), and hemoglobin, NLR was an independent predictor of in-hospital mortality [adjusted hazard ratio (aHR), 1.08; 95% CI, 1.03-1.13] and 1-year mortality (aHR, 1.08; 95% CI, 1.05-1.12). Conclusions Pre-treatment NLR at admission may be a useful biomarker for mortality and development of ARDS in patients with miliary TB.

Spirometry and Bronchodilator Test

Spirometry is a physiological test for assessing the functional aspect of the lungs using an objective indicator to measure the maximum amount of air that a patient can inhale and exhale. Acceptable spirometry testing needs to be conducted three times by an acceptable and reproducible method for determining forced vital capacity (FVC). Until the results of three tests meet the criteria of reproducibility, the test should be repeated up to eight times. Interpretation of spirometry should be clear, concise, and informative. Additionally, spirometry should guarantee optimal quality prior to the interpreting spirometry results. Our guideline adopts a fixed normal predictive value instead of the lower limit of normal as the reference value because fixed value is more convenient and also accepts FVC instead of vital capacity (VC) because measurement of VC using a spirometer is impossible. The bronchodilator test is a method for measuring the changes in lung capacity after inhaling a short-acting β-agonist that dilates the airway. When an obstructive ventilatory defect is observed, this test helps to diagnose and evaluate asthma and chronic obstructive pulmonary disease by measuring reversibility with the use of an inhaled bronchodilator. A positive response to a bronchodilator is generally defined as an increase of ≥12% and ≥200 mL as an absolute value compared with a baseline in either forced expiratory volume at 1 second or FVC.

Does repeated pleural culture increase the diagnostic yield of Mycobacterium tuberculosis from tuberculous pleural effusion in HIV-negative individuals?

Background Despite recent advances in methods for culturing Mycobacterium tuberculosis (MTB), the diagnostic yield of tuberculous pleural effusion (TBPE) remains unsatisfactory. However, unlike repeated sputum cultures of pulmonary tuberculosis, little is known about the role of repeated pleural cultures. We examined whether repeated pleural cultures are associated with increased MTB yield from TBPE. Methods A multicenter, retrospective cohort study was performed from January 2012 to December 2015 in South Korea. Patients were categorized into two groups: single- or repeated-culture groups. The diagnostic yield of MTB and clinical, radiological, and pleural fluid characteristics were evaluated. Results Among the 329 patients with TBPE, 77 (23.4%) had repeated cultures and 252 (76.5%) had a single culture. Pleural culture was performed twice in all 77 patients in the repeated-culture group at a 1-day interval (inter-quartile range, 1.0–2.0). In the repeated-culture group, the yield of MTB from the first culture was 31.2%, which was similar to that in the single-culture group (31.2% vs. 29.8%, P = 0.887). However, the yield of MTB from the second culture (10/77, 13.0%) was more than that from the first. These results may be attributable to the insufficient immune clearance for MTB invasion into the pleural space between the first and second cultures. Over time, the yield of the second cultures decreased from 17.4% to 6.7% and then 6.3%. Finally, the overall yield of MTB in the repeated- and single-culture groups was 44.2% and 29.8% respectively (P < 0.001). Conclusions The results showed that repeated pleural cultures increased MTB yield from TBPE in human immunodeficiency virus-negative individuals. Furthermore, repeated cultures may increase yield when carried out for two consecutive days.

Diet and Airway Obstruction: A Cross Sectional Study from the Second Korean National Health and Nutrition Examination Survey

Background/Aims Several dietary factors, such as antioxidant vitamins, have potential roles in the development of obstructive lung diseases. However, the results of studies on the relationships between dietary factors and obstructive lung diseases are inconsistent. The aim of this study was to determine which nutrients are related to airway obstruction (AO) in the Korean population. Methods We used data obtained as part of the Korean National Health and Nutrition Examination Survey (NHANES II) in 2001. Analysis was restricted to 1,005 adults who were 18 years of age and older, who had two or more acceptable spirometry curves, and who had participated in the nutrition examination survey. AO was defined as the ratio of forced expiratory volume in one second (FEV1) to forced vital capacity (FVC) of less than 0.7. Results Of the 1,005 study subjects, 78 (7.8%) had AO. Statistically significant factors associated with AO were 55 years of age or older (p = 0.032), central obesity (p = 0.047), hypertension (p < 0.001), smoking of 20 pack-years or more (p < 0.001), low income (p < 0.001), and low dietary protein intake expressed as a ratio of protein to recommended dietary allowance for Koreans (p = 0.037). Multiple logistic regression analyses revealed four factors that were independently associated with AO: smoking of 20 pack-years or more (odds ratio [OR], 5.801; p < 0.001), hypertension (OR, 3.905; p < 0.001), low protein intake (OR, 0.992; p = 0.004), and low income (OR, 1.962; p = 0.018). Conclusions In the Korean NHANES, smoking, hypertension, and low income were related to AO. Among dietary factors, only low protein intake was associated with AO.

Prone positioning before extracorporeal membrane oxygenation for severe acute respiratory distress syndrome: A retrospective multicenter study

OBJECTIVE To evaluate the clinical outcomes of patients with severe acute respiratory distress syndrome (ARDS) subjected to prone positioning before extracorporeal membrane oxygenation (ECMO). DESIGN A retrospective analysis of a multicenter cohort was carried out. SETTING Patients admitted to the Intensive Care Units of 11 hospitals in Korea. PATIENTS Patients were divided into those who underwent prone positioning before ECMO (n=28) and those who did not (n=34). INTERVENTIONS None. VARIABLES OF INTEREST Thirty-day mortality, ECMO weaning failure rate, mechanical ventilation weaning success rate, mechanical ventilation-free days at day 60. RESULTS The prone group had lower median peak inspiratory pressure and lower median dynamic driving pressure before ECMO. Thirty-day mortality was 21% in the prone group and 41% in the non-prone group (p=0.098). The prone group also showed a lower ECMO weaning failure rate, and a higher mechanical ventilation weaning success rate and more mechanical ventilation-free days at day 60. In the non-prone group, median dynamic compliance marginally decreased shortly after ECMO, but no significant change was observed in the prone group. CONCLUSIONS Prone positioning before ECMO was not associated to increased mortality and tended to exert a protective effect.

Age is major factor for predicting survival in patients with acute respiratory failure on extracorporeal membrane oxygenation: a Korean multicenter study

Background The proportion of elderly patients in the intensive care unit population is increasing. Although the Respiratory Extracorporeal Membrane Oxygenation Survival Prediction (RESP) score is widely used for survival prediction of extracorporeal membrane oxygenation (ECMO) patients, it is questionable whether the RESP score is applicable to older patients. The aim of this study was to investigate the applicability of the RESP score in Korean cohort. Methods Data were retrospectively analyzed from 209 acute respiratory failure (ARF) patients treated with ECMO from 2014 to 2015 at 11 hospitals. A comparison of outcome prediction models was conducted and multivariate logistic regression analysis was performed to identify independent risk factors for hospital mortality. Results In all patients, the median age was 58 (IQR, 45-65) years. Overall survival at hospital discharge was 45.9%, and veno-venous ECMO was used in 82.3% of patients. Patients older than 65 years treated with ECMO support were 51 with 31.4% of hospital survival. The PRedicting dEath for SEvere ARDS on VV-ECMO (PRESERVE) and RESP scores significantly predicted mortality in patients, with areas under the curve (AUCs) of 0.63 [95% confidence interval (CI), 0.54-0.72] and 0.66 (95% CI, 0.58-0.73), respectively. In multivariate logistic regression analysis, age is independent risk factor for hospital mortality [odds ratio 1.044 (95% CI, 1.020-1.068), P<0.001] with AUC of 0.67 (95% CI, 0.59-0.74). The RESP score was modified using reclassified age and the modified RESP score obtained AUC of 0.71 (95% CI, 0.63-0.78). Conclusions The RESP score is significant model for predicting outcomes in a Korean ECMO population. Elderly patients had higher mortality, and age alone showed similar discrimination ability for prediction of mortality compared to the RESP score.