Tumor Spheroids of an Aggressive Form of Central Neurocytoma Have Transit-Amplifying Progenitor Characteristics with Enhanced EGFR and Tumor Stem Cell Signaling

Central neurocytoma (CN) has been known as a benign neuronal tumor. In rare cases, CN undergoes malignant transformation to glioblastomas (GBM). Here we examined its cellular origin by characterizing differentiation potential and gene expression of CN-spheroids. First, we demonstrate that both CN tissue and cultured primary cells recapitulate the hierarchal cellular composition of subventricular zone (SVZ), which is comprised of neural stem cells (NSCs), transit amplifying progenitors (TAPs), and neuroblasts. We then derived spheroids from CN which displayed EGFR+/ MASH+ TAP and BLBP+ radial glial cell (RGC) characteristic, and mitotic neurogenesis and gliogenesis by single spheroids were observed with cycling multipotential cells. CN-spheroids expressed increased levels of pluripotency and tumor stem cell genes such as KLF4 and TPD5L1, when compared to their differentiated cells and human NSCs. Importantly, Gene Set Enrichment Analysis showed that gene sets of GBM-Spheroids, EGFR Signaling, and Packaging of Telomere Ends are enriched in CN-spheroids in comparison with their differentiated cells. We speculate that CN tumor stem cells have TAP and RGC characteristics, and upregulation of EGFR signaling as well as downregulation of eph-ephrin signaling have critical roles in tumorigenesis of CN. And their ephemeral nature of TAPs destined to neuroblasts, might reflect benign nature of CN.

Magnetic Resonance-Based Assessments Better Capture Pathophysiologic Profiles and Progression in Nonalcoholic Fatty Liver Disease

Background@#Several noninvasive tools are available for the assessment of nonalcoholic fatty liver disease (NAFLD) including clinical and blood biomarkers, transient elastography (TE), and magnetic resonance imaging (MRI) techniques, such as proton density fat fraction (MRI-PDFF) and magnetic resonance elastography (MRE). In the present study, we aimed to evaluate whether magnetic resonance (MR)-based examinations better discriminate the pathophysiologic features and fibrosis progression in NAFLD than other noninvasive methods. @*Methods@#A total of 133 subjects (31 healthy volunteers and 102 patients with NAFLD) were subjected to clinical and noninvasive NAFLD evaluation, with additional liver biopsy in some patients (n=54). @*Results@#MRI-PDFF correlated far better with hepatic fat measured by MR spectroscopy (r=0.978, P<0.001) than with the TE controlled attenuation parameter (CAP) (r=0.727, P<0.001). In addition, MRI-PDFF showed stronger correlations with various pathophysiologic parameters for cellular injury, glucose and lipid metabolism, and inflammation, than the TE-CAP. The MRI-PDFF and TE-CAP cutoff levels associated with abnormal elevation of serum alanine aminotransferase were 9.9% and 270 dB/m, respectively. The MRE liver stiffness measurement (LSM) showed stronger correlations with liver enzymes, platelets, complement component 3, several clinical fibrosis scores, and the enhanced liver fibrosis (ELF) score than the TE-LSM. In an analysis of only biopsied patients, MRE performed better in discriminating advanced fibrosis with a cutoff value of 3.9 kPa than the TE (cutoff 8.1 kPa) and ELF test (cutoff 9.2 kPa). @*Conclusion@#Our results suggest that MRI-based assessment of NAFLD is the best non-invasive tool that captures the histologic, pathophysiologic and metabolic features of the disease.

Tumor Spheroids of an Aggressive Form of Central Neurocytoma Have Transit-Amplifying Progenitor Characteristics with Enhanced EGFR and Tumor Stem Cell Signaling

Central neurocytoma (CN) has been known as a benign neuronal tumor. In rare cases, CN undergoes malignant transformation to glioblastomas (GBM). Here we examined its cellular origin by characterizing differentiation potential and gene expression of CN-spheroids. First, we demonstrate that both CN tissue and cultured primary cells recapitulate the hierarchal cellular composition of subventricular zone (SVZ), which is comprised of neural stem cells (NSCs), transit amplifying progenitors (TAPs), and neuroblasts. We then derived spheroids from CN which displayed EGFR+/ MASH+ TAP and BLBP+ radial glial cell (RGC) characteristic, and mitotic neurogenesis and gliogenesis by single spheroids were observed with cycling multipotential cells. CN-spheroids expressed increased levels of pluripotency and tumor stem cell genes such as KLF4 and TPD5L1, when compared to their differentiated cells and human NSCs. Importantly, Gene Set Enrichment Analysis showed that gene sets of GBM-Spheroids, EGFR Signaling, and Packaging of Telomere Ends are enriched in CN-spheroids in comparison with their differentiated cells. We speculate that CN tumor stem cells have TAP and RGC characteristics, and upregulation of EGFR signaling as well as downregulation of eph-ephrin signaling have critical roles in tumorigenesis of CN. And their ephemeral nature of TAPs destined to neuroblasts, might reflect benign nature of CN.

Magnetic Resonance-Based Assessments Better Capture Pathophysiologic Profiles and Progression in Nonalcoholic Fatty Liver Disease

Background@#Several noninvasive tools are available for the assessment of nonalcoholic fatty liver disease (NAFLD) including clinical and blood biomarkers, transient elastography (TE), and magnetic resonance imaging (MRI) techniques, such as proton density fat fraction (MRI-PDFF) and magnetic resonance elastography (MRE). In the present study, we aimed to evaluate whether magnetic resonance (MR)-based examinations better discriminate the pathophysiologic features and fibrosis progression in NAFLD than other noninvasive methods. @*Methods@#A total of 133 subjects (31 healthy volunteers and 102 patients with NAFLD) were subjected to clinical and noninvasive NAFLD evaluation, with additional liver biopsy in some patients (n=54). @*Results@#MRI-PDFF correlated far better with hepatic fat measured by MR spectroscopy (r=0.978, P<0.001) than with the TE controlled attenuation parameter (CAP) (r=0.727, P<0.001). In addition, MRI-PDFF showed stronger correlations with various pathophysiologic parameters for cellular injury, glucose and lipid metabolism, and inflammation, than the TE-CAP. The MRI-PDFF and TE-CAP cutoff levels associated with abnormal elevation of serum alanine aminotransferase were 9.9% and 270 dB/m, respectively. The MRE liver stiffness measurement (LSM) showed stronger correlations with liver enzymes, platelets, complement component 3, several clinical fibrosis scores, and the enhanced liver fibrosis (ELF) score than the TE-LSM. In an analysis of only biopsied patients, MRE performed better in discriminating advanced fibrosis with a cutoff value of 3.9 kPa than the TE (cutoff 8.1 kPa) and ELF test (cutoff 9.2 kPa). @*Conclusion@#Our results suggest that MRI-based assessment of NAFLD is the best non-invasive tool that captures the histologic, pathophysiologic and metabolic features of the disease.

Evaluation of Short-Term Exposure Levels on Ammonia and Hydrogen Sulfide During Manure-Handling Processes at Livestock Farms

Background@#Ammonia and hydrogen sulfide are harmful gases generated during aerobic/anaerobic bacterial decomposition of livestock manure. We evaluated ammonia and hydrogen sulfide concentrations generated from workplaces at livestock farms and determined environmental factors influencing the gas concentrations. @*Methods@#Five commercial swine farms and five poultry farms were selected for monitoring. Real-time monitors were used to measure the ammonia and hydrogen sulfide concentrations and environmental conditions during the manure-handling processes. Monitoring was conducted in the manure storage facility and composting facility. Information on the farm conditions was also collected through interview and walk-through survey. @*Results@#The ammonia concentrations were significantly higher at the swine composting facilities (9.5–43.2 ppm) than at other manure-handling facilities at the swine and poultry farms, and high concentrations of hydrogen sulfide were identified during the manure agitation and mixing process at the swine manure storage facilities (6.9–19.5 ppm). At the poultry manure-handling facilities, the ammonia concentration was higher during the manure-handling processes (2.6–57.9 ppm), and very low hydrogen sulfide concentrations (0–3.4 ppm) were detected. The air temperature and relative humidity, volume of the facility, duration of manure storage, and the number of animals influenced the gas concentrations. @*Conclusion@#A high level of hazardous gases was generated during manure handling, and some levels increased up to risk levels that can threaten workers' health and safety. Some of the farm operational factors were also found to influence the gas levels. By controlling and improving these factors, it would be possible to protect workers' safety and health from occupational risks.

Efficacy evaluation of syringe pump developed for continuous drug infusion

BACKGROUND: In dental intravenous sedation, continuous intravenous infusion of a low-dose drug requires an infusion pump such as a syringe pump. To develop a new syringe pump for clinical use, the functions of the pump must meet certain international standards. Various safety and efficacy tests must be performed on the syringe pump, as stipulated by these standards, and an approval must be received from the approving agency based on such test results. METHODS: The authors of the present study developed a novel syringe pump and performed efficacy evaluation by testing its infusion speed at 1 and 25 ml/h, and infusion performance testing at 2 and 24 h. Moreover, performance evaluation was conducted by comparing the novel pump to an existing pump with the infusion speed varied from 1 to 5 ml/h. RESULTS: In the efficacy testing on the newly developed syringe pump, infusion with the infusion speed initially set to 1 ml/h resulted in infusion speeds of 1.00 and 0.99 ml/h in the 2- and 24-h assessment, respectively. Changing the infusion speed setting to 25 ml/h resulted in an infusion speed of 25.09 and 23.92 ml/h in the 2- and 24-h assessment, respectively. These results show no significant differences when compared with other commercially available pumps. CONCLUSIONS: The efficacy testing of the newly developed syringe pump showed the accuracy to be within tolerance. Based on these findings, we believe that the newly developed syringe pump is suitable for clinical use.

Comparison of Real Time Nanoparticle Monitoring Instruments in the Workplaces

BACKGROUND: Relationships among portable scanning mobility particle sizer (P-SMPS), condensation particle counter (CPC), and surface area monitor (SAM), which are different metric measurement devices, were investigated, and two widely used research grade (RG)-SMPSs were compared to harmonize the measurement protocols. METHODS: Pearson correlation analysis was performed to compare the relation between P-SMPS, CPC, and SAM and two common RG-SMPS. RESULTS: For laboratory and engineered nanoparticle (ENP) workplaces, correlation among devices showed good relationships. Correlation among devices was fair in unintended nanoparticle (UNP)-emitting workplaces. This is partly explained by the fact that shape of particles was not spherical, although calibration of sampling instruments was performed using spherical particles and the concentration was very high at the UNP workplaces to allow them to aggregate more easily. Chain-like particles were found by scanning electron microscope in UNP workplaces. The CPC or SAM could be used as an alternative instrument instead of SMPS at the ENP-handling workplaces. At the UNP workplaces, where concentration is high, real-time instruments should be used with caution. There are significant differences between the two SMPSs tested. TSI SMPS showed about 20% higher concentration than the Grimm SMPS in all workplaces. CONCLUSIONS: For nanoparticle measurement, CPC and SAM might be useful to find source of emission at laboratory and ENP workplaces instead of P-SMPS in the first stage. An SMPS is required to measure with high accuracy. Caution is necessary when comparing data from different nanoparticle measurement devices and RG-SMPSs.

Smart syringe pumps for drug infusion during dental intravenous sedation

Dentists often sedate patients in order to reduce their dental phobia and stress during dental treatment. Sedatives are administered through various routes such as oral, inhalation, and intravenous routes. Intravenous administration has the advantage of rapid onset of action, predictable duration of action, and easy titration. Typically, midazolam, propofol or dexmedetomidine are used as intravenous sedatives. Administration of these sedatives via infusion by using a syringe pump is more effective and successful than infusing them as a bolus. However, during intravenous infusion of sedatives or opioids using a syringe pump, fatal accidents may occur due to the clinician's carelessness. To prevent such risks, smart syringe pumps have been introduced clinically. They allow clinicians to perform effective sedation by using a computer to control the dose of the drug being infused. To ensure patient safety, various alarm features along with a drug library, which provides drug information and prevents excessive infusion by limiting the dose, have been added to smart pumps. In addition, programmed infusion systems and target-controlled infusion systems have also been developed to enable effective administration of sedatives. Patient-controlled infusion, which allows a patient to control his/her level of sedation through self-infusion, has also been developed. Safer and more successful sedation may be achieved by fully utilizing these new features of the smart pump.

Effect of Next-Generation Exome Sequencing Depth for Discovery of Diagnostic Variants

Sequencing depth, which is directly related to the cost and time required for the generation, processing, and maintenance of next-generation sequencing data, is an important factor in the practical utilization of such data in clinical fields. Unfortunately, identifying an exome sequencing depth adequate for clinical use is a challenge that has not been addressed extensively. Here, we investigate the effect of exome sequencing depth on the discovery of sequence variants for clinical use. Toward this, we sequenced ten germ-line blood samples from breast cancer patients on the Illumina platform GAII(x) at a high depth of ~200x. We observed that most function-related diverse variants in the human exonic regions could be detected at a sequencing depth of 120x. Furthermore, investigation using a diagnostic gene set showed that the number of clinical variants identified using exome sequencing reached a plateau at an average sequencing depth of about 120x. Moreover, the phenomena were consistent across the breast cancer samples.

Genetic Analysis of Multiple Endocrine Neoplasia Type 1 (MEN1) Leads to Misdiagnosis of an Extremely Rare Presentation of Intrasellar Cavernous Hemangioma as MEN1

BACKGROUND: Multiple endocrine neoplasia type 1 (MEN1) is a rare inherited disorder characterized by the simultaneous occurrence of endocrine tumors in target tissues (mainly the pituitary, endocrine pancreas, and parathyroid glands). MEN1 is caused by mutations in the MEN1 gene, which functions as a tumor suppressor and consists of one untranslated exon and nine exons encoding the menin protein. This condition is usually suspected when we encounter patients diagnosed with tumors in multiple endocrine organs, as mentioned above. METHODS: A 65-year-old woman who underwent surgery for a pancreatic tumor (serous cystadenoma) 5 years previously was referred to our hospital due to neurologic symptoms of diplopia and left ptosis. Brain magnetic resonance imaging revealed a 3.4-cm lesion originating from the cavernous sinus wall and extending into the sellar region. It was thought to be a nonfunctioning tumor from the results of the combined pituitary function test. Incidentally, we found that she also had a pancreatic tumor, indicating the necessity of genetic analysis for MEN1. RESULTS: Genomic analysis using peripheral leukocytes revealed a heterozygous c.1621G>A mutation in the MEN1 gene that was previously reported to be either a pathogenic mutation or a simple polymorphism. We pursued a stereotactic approach to the pituitary lesion, and microscopic findings of the tumor revealed it to be an intrasellar cavernous hemangioma, a rare finding in the sellar region and even rarer in relation to oculomotor palsy. The patient recovered well from surgery, but refused further evaluation for the pancreatic lesion. CONCLUSION: There is great emphasis placed on genetic testing in the diagnosis of MEN1, but herein we report a case where it did not assist in diagnosis, hence, further discussion on the role of genetic testing in this disease is needed. Also, in cases of pituitary tumor with cranial nerve palsy, despite its low prevalence, intrasellar cavernous hemangioma could be suspected.

Application of Damage Control Resuscitation Strategies to Patients with Severe Traumatic Hemorrhage: Review of Plasma to Packed Red Blood Cell Ratios at a Single Institution

When treating trauma patients with severe hemorrhage, massive transfusions are often needed. Damage control resuscitation strategies can be used for such patients, but an adequate fresh frozen plasma: packed red blood cell (FFP:PRBC) administration ratio must be established. We retrospectively reviewed the medical records of 100 trauma patients treated with massive transfusions from March 2010 to October 2012. We divided the patients into 2 groups according to the FFP:PRBC ratio: a high-ratio (> or =0.5) and a low-ratio group (<0.5). The patient demographics, fluid and transfusion quantities, laboratory values, complications, and outcomes were analyzed and compared. There were 68 patients in the high-ratio and 32 in the low-ratio group. There were statistically significant differences between groups in the quantities of FFP, FFP:PRBC, platelets, and crystalloids administered, as well as the initial diastolic blood pressure. Bloodstream infections were noted only in the high-ratio group, and the difference was statistically significant (P=0.028). Kaplan-Meier plots revealed that the 24-hr survival rate was significantly higher in the high-ratio group (71.9% vs. 97.1%, P<0.001). In severe hemorrhagic trauma, raising the FFP:PRBC ratio to 0.5 or higher may increase the chances of survival. Efforts to minimize bloodstream infections during the resuscitation must be increased.

Development of Time-location Weighted Spatial Measures Using Global Positioning System Data

OBJECTIVES: Despite increasing availability of global positioning system (GPS), no research has been conducted to analyze GPS data for exposure opportunities associated with time at indoor and outdoor microenvironments. We developed location-based and time-weighted spatial measures that incorporate indoor and outdoor time-location data collected by GPS. METHODS: Time-location data were drawn from 38 female subjects in California who wore a GPS device for seven days. Ambient standard deviational ellipse was determined based on outdoor locations and time duration, while indoor time weighted standard deviational ellipse (SDE) was developed to incorporate indoor and outdoor times and locations data into the ellipse measure. RESULTS: Our findings indicated that there was considerable difference in the sizes of exposure potential measures when indoor time was taken into consideration, and that they were associated with day type (weekday/weekend) and employment status. CONCLUSIONS: This study provides evidence that time-location weighted measure may provide better accuracy in assessing exposure opportunities at different microenvironments. The use of GPS likely improves the geographical details and accuracy of time-location data, and further development of such location-time weighted spatial measure is encouraged.

Genetic and Clinical Characteristics of Korean Patients with Isolated Hypoparathyroidism: From the Korean Hypopara Registry Study

Isolated hypoparathyroidism (IH) shows heterogeneous phenotypes and can be caused by defects in a variety of genes. The goal of our study was to determine the clinical features and to analyze gene mutations in a large cohort of Korean patients with sporadic or familial IH. We recruited 23 patients. They showed a broad range of onset age and various values of biochemical data. Whole exome sequencing was performed on two affected cases and one unaffected individual in a family. All coding exons and exon-intron borders of GCMB, CASR, and prepro-PTH were sequenced using PCR-amplified DNA. In one family who underwent the whole exome sequencing analysis, approximately 300 single nucleotide changes emerged as candidates for genetic alteration. Among them, we identified a functional mutation in exon 2 of GCMB (C106R) in two affected cases. Besides, heterozygous gain-of-function mutations in the CASR gene were found in other subjects; D410E and P221L. We also found one single nucleotide polymorphism (SNP) in the prepro-PTH gene, five SNPs in the CASR gene, and four SNPs in the GCMB gene. The current study represents a variety of biochemical phenotypes in IH patients with the molecular genetic diagnosis of IH.

High-Resolution Actigraphic Analysis of ADHD: A Wide Range of Movement Variability Observation in Three School Courses - A Pilot Study / 대한의료정보학회지

OBJECTIVES: This study was conducted to determine whether or not newly proposed high-resolution activity features could provide a superior analytic foundation compared to those commonly used to assess transitions in children's activities, under circumstances in which the types of courses attended exert different situational effects on activity levels. METHODS: From 153 children at a local elementary school, 10 subjects with attention deficit hyperactivity disorder (ADHD) and 7 controls were recruited. Their activity data was collected using an actigraph while they attended school. Ratios of partitioned activity ranges (0.5-2.8 G) during the entire activity were extracted during three classes: art, mathematics, and native language (Korean). Extracted activity features for each participant were compared between the two groups of children (ADHD and control) using graphs and statistical analysis. RESULTS: Activity distributions between ADHD and control groups for each class showed statistically significant differences spread through the entire range in art class compared to native language and mathematics classes. The ADHD group, but not the control group, experienced many significantly different intervals (> 50%) having low to very high activity acceleration regions during the art and languages courses. CONCLUSIONS: Class content appears to influence the activity patterns of ADHD children. Monitoring the actual magnitude and activity counts in a wide range of subjects could facilitate the examination of distributions or patterns of activities. Objective activity measurements made with an actigraph may be useful for monitoring changes in activities in children with ADHD in a timely manner.

Effects of Case Type and Standardized Patient Gender on Student Performance in a Clinical Performance Examination / 한국의학교육

PURPOSE: The purpose of this study is to assess the effects of case type and gender of standardized patient on student performance in a clinical performance examination(CPX). METHODS: During 2005, an eight-station CPX was administered to fourth-year students from 4 medical schools. A total of 306 students, of which 206(67%) were male, participated in the exam. Station checklists, scored by the SPs, consisted of history taking(Hx), physical examination(PE), information sharing(IS), clinical courtesy(CC) and patient-physician interaction(PPI). A measurement of students' perceived difficulty was obtained through student questionnaires. The difference of CPX scores between male and female students were studied using Mann-Whitney's U. RESULTS: Across the gender-neutral cases, female students scored better in Hx in 2 cases. In PE, IS and CC, the only difference seen was with CC in 1 case(female students scored higher). In PPI, female students performed better than male students in all female SP cases and one male SP case, but, there was a significant student gender-SP gender interaction when averaging all cases. For the gender sensitive case, there was no significant difference in all checklist categories in the male case when student gender was considered. In the female case, female students performed better than male students only in PPI. Student questionnaires revealed that there was no significant difference in perceived difficulty between male and female students. RESULTS: The standardized patients' ratings in gender sensitive cases are not affected by the gender of standardized patients and students, except in PPI with a female case where female students performed better than male students.

Reconstruction of Large Skull Defect Using Right-Angled Zigzag Osteotomy

PURPOSE: Among the materials for cranioplasty, autogenous bone is ideal because it is less susceptible to infection and has lower rates of subsequent exposure. However, the procedure is technically demanding to perform and requires a donor site. Disadvantages further exist when the defect is large and there are attendant limitations in donor site. The authors present their experience with reconstruction of large skull defect using right-angled zigzag osteotomized outer table of autogenous calvarial bone, overcoming the limitation in donor site. METHODS: From 2000 to 2006, 9 patients were retrospectively reviewed, who had undergone reconstruction with right angled zigzag osteotomized outer table of autogenous calvarial bone. RESULTS: Aesthetically satisfactory skull shape was achieved. Major complications of infection, hematoma, plate exposure, and donor site complications of dural tear with bleeding, cerebrospinal fluid leak, and meningitis were not seen. One patient had delayed wound healing and was successfully managed conservatively. CONCLUSION: Autogenous bone is the material of choice for cranioplasty, especially in complicated cases. Right angled zigzag osteotomy is a useful method in reconstruction of large skull defects with less donor site morbidity.

The Effects of Information Sharing between Students on Results of Clinical Performance Examination / 한국의학교육

PURPOSE: This study was designed to investigate the effects of information sharing between students on results of clinical performance examination (CPX). METHODS: 143 third-year students, who completed their core clinical clerkship, were randomly assigned to one day of a 3-day, 6 station CPX. Station checklists, scored by the SP(s), consisted of history taking, physical examination, information sharing, clinical courtesy and patient-physician interaction. We compared the CPX station scores, CPX domain scores, self assessment scores and GPA of the three groups tested on different days with ANOVA, and analyzed the differences in CPX scores, after controlling for GPA, with ANCOVA. The correlations among the CPX total and domain scores, self assessment and the GPA of the 3rd year students were calculated. Data regarding information sharing between students and self-assessment were obtained through student questionnaires. RESULTS: CPX total scores, self assessment scores and GPA of 3rd year students from day-2 were significantly higher than scores from day-1 or day-3. Checklist analysis showed that PE, CC and PPI scores were significantly higher on day-2, but Hx and IS scores were not significantly different. Results from questionnaires showed that 43% of students shared evaluation information. And CPX total scores had little correlation with self assessment scores. GPA of 3rd year students showed a similar pattern with the CPX totalscore. CONCLUSION: There is information sharing occurring between students during clinical performance examinations. Although there are significant differences in CPXscores for the treatment group, it seemed that CPX scores are not affected by information sharing between students. Reliability of information sharing from other students is low. The generalization of this study should be interpreted carefully.

Determinations of personal carbon monoxide exposure and blood carboxyhemoglobin levels in Korea

Determinant factors for personal carbon monoxide (CO) exposures were sought in Korea, where CO poisoning has been a major public health problem due to coal briquette (Yeontan) combustion for space heating and cooking. Personal 24-hr CO exposures of 15 housewives were measured by CO passive samplers on 2 days of the week (Wednesday and Sunday). Blood samples were taken to measure carboxyhemoglobin (COHb) just after the exposure sampling. Average CO exposure and COHb level were 5.6 ppm and 2.4%, respectively. Personal CO exposures as well as COHb levels were significantly increased by the use of Yeontan, especially on a weekday. Carboxyhemoglobin levels were closely related to the time between blood collection and replacement of Yeontan: the closer the blood collection was to replace Yeontan, the higher the COHb levels were. Assuming a background COHb of 1.34%, COHb increased on average by 1.8% with a 24-hr personal CO exposure of 10 ppm. The relationship between CO exposure and COHb level was provided by simultaneous direct measurements in real environment, although a measurement of COHb at the end of exposure could not represent previous 24-hr exposure thoroughly.