Biomedical subjects

K S Chan

Publications and source records attributed to K S Chan.

At least 19 recordsLinked to original sources

PubMed2006

Application of two-dimensional spectral surface plasmon resonance to imaging of pressure distribution in elastohydrodynamic lubricant films.

What we believe to be a novel two-dimensional spectral surface plasmon resonance imaging technique determining pressure distribution in elastohydrodynamic lubricant films is presented. This technique makes use of the spectral characteristics associated with the surface plasmon resonance (SPR) effect, and it provides more spectral information in refractive index mapping than conventional contrast SPR imaging. Two-dimensional imaging is demonstrated and applied to a highly pressurized liquid lubricant trapped inside an elastohydrodynamic lubrication (EHL) dimple. The hydrostatic pressure inside the EHL dimple causes a localized change of the refractive index of the lubrication oil. This also results in a shift in the spectral SPR absorption dip. By monitoring the color changes within the SPR image and calibrating with lubricants of known refractive index profiles, we can obtain a direct measurement of the refractive index distribution within the EHL dimple. PB 2400 lubricant dimples were studied in our experiments. The proposed SPR imaging approach is irrespective of the absolute lubricant film thickness h, therefore overcoming the major limitations of a conventional optical interference technique. With further development of the two-dimensional refractive index mapping technique, widespread applications in various fields are possible, including high-throughput sensors and the detection of bioaffinity interactions.

Journal Article↗

PubMed2006

Computed tomography features of spontaneously perforated pyometra: a case report.

Spontaneous perforation of pyometra is an extremely rare emergent gynecologic disease. We report a 73-year-old woman with a spontaneously perforated pyometra presenting with acute abdomen in the emergency department. A dedicated computed tomography examination of the abdominal and pelvic regions revealed the diagnosis. The patient recovered well after surgical intervention and antibiotic treatment.

Abdomen, Acute↗

PubMed2006

Reliability, validity, and responsiveness of a 2-min walk test to assess exercise capacity of COPD patients.

PURPOSES: To investigate the reliability, validity, and responsiveness of a 2-min walk test (2MWT) in Chinese COPD patients with moderate-to-severe disease. METHODS: This study consisted of two parts. Forty-seven stable COPD patients with moderate-to-severe disease participated in the first part of study for the investigation of reliability and validity. The demographic and anthropomorphic data collected included age, gender, body weight, height, and body mass index. Each subject performed a pulmonary function test, a cardiopulmonary exercise test, three trials of a 2MWT, and two trials of 6-min-walk test (6MWT) in random order within a 5-day period. Fifteen of these subjects participated in the second part of study for the evaluation of the responsiveness of the 2MWT following pulmonary rehabilitation. The 2MWT and 6MWT were conducted before and after the program for comparison. RESULTS: Forty-five subjects (mean [+/- SD] age, 71.8 +/- 8.3 years; mean FEV1, 0.88 +/- 0.27 L) completed the first part of study, and 9 subjects (mean age, 74 +/- 8.7 years; mean FEV1, 0.94 +/- 0.28 L) completed the second part of study. The intraclass correlation coefficient of the repeated 2MWTs was high (R = 0.9994; p < 0.05), mean differences across trials ranged from 0.3 to 0.8 m (95% confidence interval, -3.1 to 4.6 m) demonstrated its high test-retest reliability. Significant correlations were found between the 2MWT and the 6MWT, the maximum oxygen uptake (V(O2)max) in milliliters per minute, and the V(O2)max in milliliters per kilogram per minute (r = 0.937, 0.454, and 0.555 respectively; p < 0.0125). Following rehabilitation, there were significant improvements in the mean 2MWT and 6MWT walking distance of 17.2 +/- 13.8 m and 60.6 +/- 35.5 m, respectively, with moderate effect sizes (0.61 and 0.53, respectively) and large standardized mean responses (1.25 and 1.70, respectively). High correlation was found between changes in the 2MWT and the 6MWT (r = 0.70; p < 0.05). CONCLUSION: The 2MWT was shown to be a reliable and valid test for the assessment of exercise capacity and responsive following rehabilitation in patients with moderate-to-severe COPD. It is practical, simple, and well-tolerated by patients with severe COPD symptoms.

Aged↗

PubMed2005

Ab initio and variational transition state approach to beta-C3N4 formation: kinetics for the reaction of CH3NH2 with H.

The CH3NH2 molecule has been considered as either an important intermediate in methane and ammonia mixtures or a precursor in methylamine and hydrogen mixtures in the synthesis of carbon nitride thin films. The fast Hydrogen (H) abstraction from CH3NH2 is an important process involved in the formation of HCN or CNH in the chemical vapor deposition (CVD) of carbon nitride thin films. The energetic and kinetic characteristics of the H abstraction reaction from CH3NH2 by atomic H used in CVD of beta-C3N4 were studied using ab initio direct dynamics methods for the first time. Two primary processes were identified for this reaction: H abstraction from the CH3 group and H abstraction from the NH2 group. On the basis of ab initio data, the rate constants of each channel have been deduced by canonical variational transition state theory with small-curvature tunneling correction over a wide temperature range of 200 to approximately 3000 K. The theoretical results were compared with available experimental data.

Journal Article↗

PubMed2005

[Matrix metalloproteinases and their inhibitors in lung cancer with malignant pleural effusion].

UNLABELLED: Matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) play a crucial role in physiological and pathological matrix turnover. This study aimed to determine the occurrence of MMP and TIMP in lung cancer patients with malignant pleural effusions (CA). METHODS: MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, TIMP-1, and IMP-2 oncentrations were determined by ELISA and zymography in pleural effusions and plasma of 31 CA and 14 congestive heart failure (CHF) patients and in plasma of 18 healthy controls (CON). RESULTS: MMP-2, TIMP-1, and TIMP-2 ELISA-concentrations were increased in CA pleural fluid vs. CA plasma (p < 0.005, p < 0.005, p < 0.05), in contrast to MMP-9 being higher in plasma (p < 0.005). Pleural fluid MMP-1 and MMP-8 were increased in CA vs. CHF (p < 0.05, p < 0.005). MMP and TIMP plasma concentrations were not different in CA vs. CHF, but MMP-9, TIMP-1, and TIMP-2 were increased vs. CON (p < 0.005, each). Gelatine zymography MMP-9/MMP-2 ratios were increased in CA plasma vs. effusion fluid (p < 0.005), in CA vs. CHF plasma, CA vs. CHF effusions (p < 0.005 each), and in CA vs. CON plasma (p < 0.05). CONCLUSIONS: MMP-2, TIMP-1, and TIMP-2 accumulate in the pleural compartment in CA and CHF, probably reflecting an unspecific pleural reaction. MMP-1 and MMP-8 are increased in cellular rich CA pleural effusions only. The determination of MMP-9/MMP-2 ratios in pleural fluid may contribute to differentiate CHF from CA effusions.

Enzyme-Linked Immunosorbent Assay↗

PubMed2005

Duration of RT-PCR positivity in severe acute respiratory syndrome.

Severe acute respiratory syndrome (SARS) is a highly infectious respiratory infection with a high mortality. The duration of infectivity is unknown. The RT-PCR positivity for SARS-associated coronavirus (SARS-CoV) was followed in 45 virologically confirmed SARS patients. Serial RT-PCRs for SARS-CoV were performed in the nasopharyngeal aspirate, stool and urine of 45 SARS patients who survived until discharge. All patients had at least one site that was positive for SARS-CoV on presentation. Time to RT-PCR conversion was studied in all patients. There were 15 males (33.3%) and 30 females (66.7%), with a mean+/- SD age of 40.7+/-14.7 yrs. The median (range) time of RT-PCR conversion was 30 days (2-81). On discharge from the hospital, 18 (40%) remained RT-PCR positive in at least one site. For patients with positive RT-PCR on discharge, the median (range) time to RT-PCR conversion after discharge was 13 days (2-60). A significant proportion of severe acute respiratory syndrome patients remained RT-PCR positive for severe acute respiratory syndrome-associated coronavirus for a substantial duration after discharge. The clinical significance is unknown and this finding merits further study. It is prudent to advise patients to adhere to strict personal hygiene on discharge until RT-PCR becomes negative.

Adolescent↗

PubMed2005

Vascular endothelial growth factor in pleural effusions of different origin.

This study aimed to determine the diagnostic relevance of vascular endothelial growth factor (VEGF) in the pleural fluid and serum of patients with pleural effusions of different aetiology. VEGF was quantified in the pleural effusion fluid and serum of 96 patients with malignancies (58 lung cancers (CA) and 38 tumours with secondaries to the lung (TM)), 45 with congestive heart failure (CHF), 28 with tuberculosis (TB), 45 with acute infections (INF), and in the serum of 20 healthy controls. VEGF pleural effusion concentrations were significantly different in the main diagnostic groups. VEGF was higher in effusions of patients with malignancies (CA as well as TM) in comparison with INF, TB or CHF. In serum, however, high VEGF concentrations indicated CA, TM or INF, but not TB or CHF. Despite significant differences of VEGF levels in different patient groups, receiver-operating characteristic analysis revealed insufficient diagnostic value of VEGF for differential diagnosis of pleural effusions. In conclusion, vascular endothelial growth factor serum concentration is highly suggestive of the presence of lung disease in general, except for tuberculosis. In effusion fluid, the presence of vascular endothelial growth factor clearly indicates inflammatory or malignant origin. However, for diagnostic use, additional parameters besides vascular endothelial growth factor are mandatory.

Adult↗

PubMed2004

Viral replication in the nasopharynx is associated with diarrhea in patients with severe acute respiratory syndrome.

The role of severe acute respiratory syndrome (SARS) coronavirus as an enteric pathogen was investigated in a cohort of 142 patients with SARS who were treated with a standard treatment protocol. Data from daily hematological, biochemical, radiological, and microbiological investigations were prospectively collected, and the correlation of these findings with diarrhea was retrospectively analyzed. Sixty-nine patients (48.6%) developed diarrhea at a mean (+/- standard deviation [SD]) of 7.6+/-2.6 days after the onset of symptoms. The diarrhea was most severe at a mean (+/-SD) of 8.8+/-2.4 days after onset, with a maximum frequency of 24 episodes per day (median, 5 episodes; range, 3-24 episodes). A higher mean virus load in nasopharyngeal specimens obtained on day 10 after the onset of symptoms was significantly associated with the occurrence of diarrhea (3.1 log10 vs. 1.8 log10 copies/mL; P=.01) and mortality (6.2 vs. 1.7 log10 copies/mL; P<.01). However, diarrhea was not associated with mortality. The lung and the gastrointestinal tract may react differently to SARS coronavirus infection. Additional investigation of the role of SARS coronavirus in the pathogenesis of diarrhea in patients with SARS should be conducted.

Adult↗

PubMed2004

[Pleuritis tuberculosa - therapeutic value of repeated chest tapping].

Tuberculous pleuritis tends to develop fibrosis to a high degree. The use of corticosteroids enhances the absorption of pleural effusions, the residual pleural thickening, however, remains unaffected. Whether repeated chest tapping in patients with persistent effusions in addition to antituberculous therapy favourably influences the outcome is not known. Therefore, patients with tuberculous pleuritis were examined in a prospective, randomized study. After confirmation of the diagnosis patients were randomized in group A with antituberculous treatment (Isoniazid, Rifampicin, Pyrazinamid, and Streptomycin) alone or in group B with additional pleural tapping for four weeks (phase I). In phase II patients in both groups with persistent effusions received oral prednisolone (0,75 mg/kg body weight) tapered over four weeks. The extent of pleural effusions was determined by chest X-ray. Roentgenological changes were evaluated at the end of the observation period. Lung function tests by spirometry were performed after two, four, eight weeks, and at the last follow up visit. At the end of phase I no pleural effusion could be observed roentgenologically in group A in 7 of 16 patients (44 %) and in group B in 10 of 16 patients (63 %) (p = n. s.). At the end of phase II extensive residual thickening was observed in one patient (group B) necessitating pleurectomy six months later. The lung function parameters demonstrated a restrictive pattern, which did not differ significantly at the end of the observation period. After a mean follow-up period of four months none or minimal residual changes could be observed radiologically in the remaining patients. In summary, despite the low number of patients examined, this study shows that in patients with tuberculous pleuritis repeated chest tapping in addition to antituberculous medication does not seem to benefit the patient, as neither the degree of residual pleural thickening nor the restrictive lung function impairment seem to be influenced significantly.

Adult↗

PubMed2004

[Immunohistochemical localization of matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) in tuberculous pleuritis].

Matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) have been found by ELISA and gelatine zymography in different concentrations in pleural fluid in tuberculous (TB) pleuritis. For further differentiation MMP and TIMP were localized in pleural biopsies by immunhistochemical staining with antibodies directed against MMP-1, MMP-2, MMP-3, MMP-9, TIMP-1, and TIMP-2 using the Labelled-Avidin-Biotin (LAB). Immunohistological reactivity of MMP-1 was found in epitheloidcellular histiocytes, Langhans' giant cells, lymphocytes, macrophages, as well as in fibroblasts of granulomatous reactions. MMP-2 was found in a few epitheloid cellular histiocytes, fibroblasts, and inflammatory cells. MMP-3 was weakly positive in a few lymphocytes only. MMP-9 was found in a few fibroblasts, epitheloid cells, and inflammatory cells, foremost, however, in pleural mesothial cells. A few fibroblasts only showed immunoreactivity of TIMP-1 and TIMP-2. The observed inhomogenous staining pattern could be explained by the different state of activation of individual cellular units. In conclusion, the immunohistochemical demonstration of MMP and TIMP in pleural cells and tissue structures indicates their local involvement in fibrosing reactions in TB-pleuritis.

Female↗

PubMed2004

Testing for common structures in a panel of threshold models.

We consider the problem of examining the extent of (partial) similarity in the dynamics of a panel of independent threshold autoregressive processes. We develop some tests for common structure via Wald's approach and by checking whether the parameter estimates of the unconstrained threshold models satisfy the constraints defining the common structure. One test concerns the equality of independent ratios of normal means, which is shown to have nonstandard asymptotic null distribution. These tests are illustrated with a modern panel of Canadian lynx data; our analysis suggests that the lynx data over Canada share similar dynamics in the decrease phase, but they appear to be different in the increase phase.

Animals↗

PubMed2004

Role of lopinavir/ritonavir in the treatment of SARS: initial virological and clinical findings.

BACKGROUND: The clinical response of patients with severe acute respiratory syndrome (SARS) to a combination of lopinavir/ritonavir and ribavirin was examined after establishing the in vitro antiviral susceptibility of the SARS associated coronavirus to a panel of antiviral agents. METHODS: The in vitro susceptibility of the prototype of SARS associated coronavirus to a panel of nucleoside analogues and protease inhibitors currently licensed for clinical use was studied. Forty one patients with SARS followed for 3 weeks were treated with a combination of lopinavir/ritonavir and ribavirin. The clinical progress and virological outcomes were monitored and compared with 111 patients treated with ribavirin only who served as historical controls. RESULTS: In vitro antiviral activity against SARS associated coronavirus was demonstrated for lopinavir and ribavirin at concentrations of 4 micro g/ml and 50 micro g/ml, respectively, only at 48 hours. The adverse clinical outcome (ARDS or death) was significantly lower in the treatment group than in the historical controls (2.4% v 28.8%, p<0.001) at day 21 after the onset of symptoms. The adverse outcome remained significantly lower in the treatment group than in the controls-both those diagnosed early (p<0.001) and those diagnosed later in the course of the epidemic (p = 0.002)-but there was no significant difference in adverse outcome rates between the two time periods (p = 0.548). No time related difference in outcome was observed in the control groups. A reduction in steroid usage and nosocomial infections was seen in patients initially treated with lopinavir/ritonavir, and these patients had a decreasing viral load and rising peripheral lymphocyte count. Multivariate analysis showed that age, hepatitis B carrier status, and lack of treatment with this antiviral combination were independent predictors of an adverse outcome. Lopinavir/ritonavir treatment was associated with a better outcome even when adjusted for baseline lactate dehydrogenase level. CONCLUSIONS: The apparent favourable clinical response with lopinavir/ritonavir and ribavirin supports further randomised placebo controlled trials in patients with SARS.

Adult↗

PubMed2004

Spontaneous pneumomediastinum in patients with severe acute respiratory syndrome.

Spontaneous pneumomediastinum (SP) unrelated to assisted ventilation is a newly recognised complication of severe acute respiratory syndrome (SARS). The objective of the present study was to examine the incidence, risk factors and the outcomes of SP in a cohort of SARS victims from a community outbreak. Data were retrieved from a prospectively collected database of virologically confirmed SARS patients. One hundred and twelve cases were analysable, with 13 patients developing SP (11.6%) at a mean +/- SD of 19.6 +/- 4.6 days from symptom onset. Peak lactate dehydrogenase level was associated with the development of SP. SP was associated with increased intubation and a trend towards death. Drainage was required in five cases. For patients who survived, the SP and/or the associated pneumothoraces took a median of 28 days (interquartile range: 15-45 days) to resolve completely. In conclusion, spontaneous pneumomediastinum appeared to be a frequent complication of severe acute respiratory syndrome. Further research is needed to investigate its pathogenesis.

Adult↗

PubMed2004

Viral loads in clinical specimens and SARS manifestations.

A retrospective viral load study was performed on clinical specimens from 154 patients with laboratory-confirmed severe acute respiratory syndrome (SARS); the specimens were prospectively collected during patients' illness. Viral load in nasopharyngeal aspirates (n = 142) from day 10 to day 15 after onset of symptoms was associated with oxygen desaturation, mechanical ventilation, diarrhea, hepatic dysfunction, and death. Serum viral load (n = 53) was associated with oxygen desaturation, mechanical ventilation, and death. Stool viral load (n = 94) was associated with diarrhea, and urine viral load (n = 111) was associated with abnormal urinalysis results. Viral replications at different sites are important in the pathogenesis of clinical and laboratory abnormalities of SARS.

Adult↗

PubMed2003

Clinical progression and viral load in a community outbreak of coronavirus-associated SARS pneumonia: a prospective study.

BACKGROUND: We investigated the temporal progression of the clinical, radiological, and virological changes in a community outbreak of severe acute respiratory syndrome (SARS). METHODS: We followed up 75 patients for 3 weeks managed with a standard treatment protocol of ribavirin and corticosteroids, and assessed the pattern of clinical disease, viral load, risk factors for poor clinical outcome, and the usefulness of virological diagnostic methods. FINDINGS: Fever and pneumonia initially improved but 64 (85%) patients developed recurrent fever after a mean of 8.9 (SD 3.1) days, 55 (73%) had watery diarrhoea after 7.5 (2.3) days, 60 (80%) had radiological worsening after 7.4 (2.2) days, and respiratory symptoms worsened in 34 (45%) after 8.6 (3.0) days. In 34 (45%) patients, improvement of initial pulmonary lesions was associated with appearance of new radiological lesions at other sites. Nine (12%) patients developed spontaneous pneumomediastinum and 15 (20%) developed acute respiratory distress syndrome (ARDS) in week 3. Quantitative reverse-transcriptase (RT) PCR of nasopharyngeal aspirates in 14 patients (four with ARDS) showed peak viral load at day 10, and at day 15 a load lower than at admission. Age and chronic hepatitis B virus infection treated with lamivudine were independent significant risk factors for progression to ARDS (p=0.001). SARS-associated coronavirus in faeces was seen on RT-PCR in 65 (97%) of 67 patients at day 14. The mean time to seroconversion was 20 days. INTERPRETATION: The consistent clinical progression, shifting radiological infiltrates, and an inverted V viral-load profile suggest that worsening in week 2 is unrelated to uncontrolled viral replication but may be related to immunopathological damage.

Administration, Oral↗

PubMed2003

The development of the Chinese version of Impact of Event Scale--Revised (CIES-R).

BACKGROUND: This is an exploratory study on the psychometric properties and normative data of the Chinese translation of the Impact of Event Scale - Revised (CIES-R). METHODS: The original Impact of Event Scale - Revised was translated into Chinese and the comparability of content was verified through back-translation procedures. The study consisted of a sample of 116 patients from the Accident and Emergency Department. RESULTS: The reliability of the Chinese version was verified. The validity of the Chinese version as a measure of psychological distress was supported by the positive correlations between the various subscale scores of CIES-R (i. e., Intrusion, Avoidance, and Hyperarousal) and General Health Questionnaire-20. However, the independence of the three subscales was not supported. CONCLUSIONS: The present result suggests that normative information for different age groups and clinical samples might be different. Further study with clinical sample and investigation of the relationship between CIES-R and other diagnostic measures of PTSD are discussed.

Adolescent↗

PubMed2003

SARS: prognosis, outcome and sequelae.

Severe acute respiratory syndrome (SARS) is associated with considerable morbidity and mortality in the acute phase. Worldwide case fatality rate is 11% (range 7 to 27%) for the most severely affected regions. Several adverse prognostic factors have been identified, including advanced age, presence of comorbidity, higher lactose dehydrogenase levels and initial neutrophil count, but the impact of viral and other host factors on outcome is unknown. Published data on sequelae of SARS are limited. Clinical follow-up of patients who recovered from SARS has demonstrated radiological, functional and psychological abnormalities of varying degrees. In the early rehabilitation phase, many complained of limitations in physical function from general weakness and/or shortness of breath. In a small series of subjects who underwent CT scan of the chest, over half showed some patchy changes consistent with pulmonary fibrosis. Lung function testing at 6-8 weeks after hospital discharge showed mild or moderate restrictive pattern consistent with muscle weakness in 6-20% of subjects. Mild decrease in carbon monoxide diffusing capacity was detected in a minority of subjects. Preliminary evidence suggests that these lung function abnormalities will improve over time. Psychobehavioural problems of anxiety and/or depression were not uncommon in the early recovery phase, and improved over time in the majority of patients. Avascular necrosis of the hip has been reported as another complication. The long-term sequelae of SARS are still largely unknown. It is important to follow up these patients to detect and appropriately manage any persistent or emerging long-term sequelae in the physical, psychological and social domains.

Humans↗

PubMed2003

Treatment of severe acute respiratory syndrome with lopinavir/ritonavir: a multicentre retrospective matched cohort study.

OBJECTIVES: To investigate the possible benefits and adverse effects of the addition of lopinavir/ritonavir to a standard treatment protocol for the treatment of severe acute respiratory syndrome. DESIGN: Retrospective matched cohort study. SETTING: Four acute regional hospitals in Hong Kong. PATIENTS AND METHODS: Seventy-five patients with severe acute respiratory syndrome treated with lopinavir/ritonavir in addition to a standard treatment protocol adopted by the Hospital Authority were matched with controls retrieved from the Hospital Authority severe acute respiratory syndrome central database. Matching was done with respect to age, sex, the presence of co-morbidities, lactate dehydrogenase level and the use of pulse steroid therapy. The 75 patients treated with lopinavir/ritonavir were divided into two subgroups for analysis: lopinavir/ritonavir as initial treatment, and lopinavir/ritonavir as rescue therapy. These groups were compared with matched cohorts of 634 and 343 patients, respectively. Outcomes including overall death rate, oxygen desaturation, intubation rate, and use of pulse methylprednisolone were reviewed. RESULTS: The addition of lopinavir/ritonavir as initial treatment was associated with a reduction in the overall death rate (2.3%) and intubation rate (0%), when compared with a matched cohort who received standard treatment (15.6% and 11.0% respectively, P<0.05) and a lower rate of use of methylprednisolone at a lower mean dose. The subgroup who had received lopinavir/ritonavir as rescue therapy, showed no difference in overall death rate and rates of oxygen desaturation and intubation compared with the matched cohort, and received a higher mean dose of methylprednisolone. CONCLUSION: The addition of lopinavir/ritonavir to a standard treatment protocol as an initial treatment for severe acute respiratory syndrome appeared to be associated with improved clinical outcome. A randomised double-blind placebo-controlled trial is recommended during future epidemics to further evaluate this treatment.

Adolescent↗