Biomedical subjects

C M Lim

Publications and source records attributed to C M Lim.

At least 19 recordsLinked to original sources

PubMed2006

Cardiac state diagnosis using adaptive neuro-fuzzy technique.

Analysis of heart rate has become a popular noninvasive tool for assessing the activities of the autonomic nervous system (ANS). These signals may either contain indicators of a current disease or even warnings about impending diseases. However, to manually study and pinpoint heart abnormalities in voluminous data is strenuous and time consuming. Here, an adaptive neuro-fuzzy network is used to classify heart abnormalities in 10 different cardiac states and shown to be effective. The results indicate a high level of efficacy of tools used with an accuracy level of more than 94%.

Algorithms↗

PubMed2005

Characterization of EEG--a comparative study.

The Electroencephalogram (EEG) is a representative signal containing information about the condition of the brain. The shape of the wave may contain useful information about the state of the brain. However, the human observer cannot directly monitor these subtle details. Besides, since bio-signals are highly subjective, the symptoms may appear at random in the time scale. Therefore, the EEG signal parameters, extracted and analyzed using computers, are highly useful in diagnostics. Chaotic measures like correlation dimension (CD), largest Lyapunov exponent (LLE), Hurst exponent (H) and entropy are used to characterize the signal. Results indicate that these nonlinear measures are good discriminators of normal and epileptic EEG signals. These measures distinguish epileptic EEG and alcoholic from normal EEG with an accuracy of more than 90%. The dynamical behavior is less random for alcoholic and epileptic compared to normal. This indicates less of information processing in the brain due to the hyper-synchronization of the EEG. Hence, the application of nonlinear time series analysis to EEG signals offers insight into the dynamical nature and variability of the brain signals. As a pre-analysis step, the EEG data is tested for nonlinearity using surrogate data analysis and the results exhibited a significant difference in the correlation dimension measure of the actual data and the surrogate data.

Alcoholism↗

PubMed2004

Classification of cardiac abnormalities using heart rate signals.

The heart rate is a non-stationary signal, and its variation can contain indicators of current disease or warnings about impending cardiac diseases. The indicators can be present at all times or can occur at random, during certain intervals of the day. However, to study and pinpoint abnormalities in large quantities of data collected over several hours is strenuous and time consuming. Hence, heart rate variation measurement (instantaneous heart rate against time) has become a popular, non-invasive tool for assessing the autonomic nervous system. Computer-based analytical tools for the in-depth study and classification of data over day-long intervals can be very useful in diagnostics. The paper deals with the classification of cardiac rhythms using an artificial neural network and fuzzy relationships. The results indicate a high level of efficacy of the tools used, with an accuracy level of 80-85%.

Arrhythmias, Cardiac↗

PubMed2004

Effect of reflexology on EEG--a nonlinear approach.

Reflexology is a 4000-year-old art of healing practiced in ancient India, China and Egypt. In the beginning of the 20th century, it spread to the Western world. Reflexologic clinics and massage centers can be found all around the world. In spite of the widespread popularity, to the best of our knowledge, no serious research work has been done in this area, although much scientific research work has been carried out in other Eastern techniques like meditation and yoga. This is why a humble attempt is done in this work to quantitatively assess the effect of reflexological stimulation from a systems point of view. In this work, nonlinear techniques have been used to assess the complexity of EEG with and without reflexological stimulation. We prefer the nonlinear approach, as we believe that the effects are taking place in a subtle way, since there is no direct correlation between reflexological points and modern neuroanatomy.

Algorithms↗

PubMed2002

Pseudocyst of the auricle.

OBJECTIVE: To study the epidemiological profile of patients with pseudocyst of the auricle and to review the effectiveness of surgical excision of the anterior cartilage with compression buttoning in this condition. STUDY DESIGN: Medical records of patients with pseudocyst of the auricle treated in the Department of Otolaryngology of the Singapore General Hospital were reviewed retrospectively during the period from March 1, 2000, to November 30, 2001. METHODS: A retrospective descriptive analysis of the epidemiological profile of patients with pseudocyst of the auricle was done. Surgical excision with compression buttoning was evaluated as the definitive treatment in this condition. RESULTS: Eighty-seven percent of our patients were male and the mean age was 38.9 years old. There was no racial predisposition. All 9 patients who had simple aspiration of the cyst had prompt re-accumulation of the pseudocyst. None of the patients had recurrence following excision and compression buttoning of the pseudocyst. The complication rate in our study was 2.4%. Only one patient developed initial perichondritis with a resultant cauliflower deformity following surgical excision. CONCLUSION: Pseudocyst of the auricle typically presents as a painless unilateral swelling of the auricle in young adult males. Treatment options are varied. Excision of the anterior cartilage with compression buttoning yielded excellent results with no recurrence.

Adult↗

PubMed2001

Pathogenic role of endothelin 1 in hemodynamic dysfunction in experimental acute pulmonary thromboembolism.

The plasma endothelin-1 (ET-1) level is elevated in patients with acute pulmonary thromboembolism (APE). Whether ET-1 is a pathogenic mediator or a simple marker of APE is not known. We investigated the role of ET-1 in hemodynamic dysfunction in APE through evaluating the effects of ET(A) receptor antagonist in an experimental APE model. We also examined ET-1 expression in embolized lungs. In a canine autologous blood clot pulmonary embolism model, ET(A) receptor antagonist ZD2574 (10 mg/kg, intravenous; ZD2574 group; n = 6) or vehicle (control group; n = 5) was administered. Hemodynamic and gas exchange parameters and plasma levels of ET-1 were serially measured. Prepro-ET-1 mRNA expression and the distribution of ET-1 peptide in lung tissues were also examined. With ZD2574 pulmonary arterial pressure and pulmonary vascular resistance significantly decreased, and were lower compared with the control group. The decrease in cardiac output was also less in the ZD2574 group. Plasma ET-1 levels increased after embolization. Prepro-ET-1 mRNA expression increased in embolized lungs and ET-1 peptide expression also increased in embolized lungs, particularly in the muscular pulmonary arteries, compared with normal lungs. These findings suggest that ET-1 partially contributes to hemodynamic derangements of APE, and that ET(A) receptor antagonists might constitute a useful therapeutic tool for APE.

Acute Disease↗

PubMed2001

Comparison of the response to the prone position between pulmonary and extrapulmonary acute respiratory distress syndrome.

OBJECTIVES: To determine whether the response to the prone position differs between acute respiratory distress syndrome (ARDS) resulting from a pulmonary cause (ARDSp) and that from an extrapulmonary cause (ARD-Sexp). DESIGN AND SETTING: Prospective observational study in a medical ICU of a university-affiliated hospital. SUBJECTS: A consecutive series of 31 patients with ARDSp and 16 with ARDSexp within 3 days of onset of ARDS. INTERVENTION: Prone position for at least 2 h. MEASUREMENTS AND RESULTS: In ARDSp, compared with the supine position (121 +/- 49 mmHg), PaO2/FIO2 was not increased after 0.5 h but was increased after 2 h in the prone position (158 +/- 60 mmHg). In ARDSexp, compared with the supine position (106 +/- 53 mmHg), PaO2/FIO2 was increased after 0.5 h (155 +/- 91 mmHg), but was not further changed after 2 h. Marked oxygenation response (increase in PaO2/FIO2 > 40% from baseline) after 0.5 h was 23% in ARDSp and 63% in ARDSexp, and that after 2 h was 29% and 63%, respectively. Static respiratory compliance decreased in the prone position in ARDSexp (30 +/- 11 ml/cmH2O at baseline, 27 +/- 11 after 0.5 h and 25 +/- 9 after 2 h) but not in ARDSp. Consolidation score as determined on the first chest radiography taken in the prone position decreased to a greater degree in ARDSexp (-2.4 +/- 4.1) than in ARDSp (0.3 +/- 4.1). CONCLUSION: Pulmonary ARDS and extrapulmonary ARDS in their early stages respond differently to the prone position with regard to the time course of oxygenation, respiratory mechanical behaviour, and radiographic change. These findings suggest that the early pathophysiology of ARDS differs according to the type of primary insult to the lung.

Aged↗

PubMed2001

Effect of ventilation mode on gas exchange during partial liquid ventilation at different perfluorocarbon doses in surfactant-depleted lung.

Although gas ventilation is an integral part of partial liquid ventilation (PLV), the role of ventilation mode during PLV is not established, especially at a varying perfluorocarbon dose. In 10 surfactant-depleted rabbits, PLV was performed at a low dose (10 ml/kg) and at a functional residual capacity (FRC) dose (30 ml/kg) of perfluorodecalin in pressure-control (PC) and volume-control (VC) modes in balanced sequence. In these four PLV trials, PC mode was adjusted to be identical to VC mode with regard to tidal volume and inspiratory-to-expiratory ratio. PaO2 during PLV in PC mode was higher than in VC mode at the Low dose (159 plus minus 93 mm Hg, 115 plus minus 75 mm Hg, respectively: p = 0.005) and at the FRC dose (228 +/- 114 mm Hg, 164 +/- 104 mm Hg, respectively: p = 0.002). PaCO2 during PLV in PC mode was lower than in VC mode at the Low dose (59 +/- 18 mm Hg, 72 +/- 20 mm Hg, respectively: p = 0.005), whereas PaCO2 at the FRC dose was not different between modes. Curves of inspiratory flow appeared least deformed with PLV in PC mode at the Low dose, whereas they were saw-tooth deformed with PLV in VC mode at both doses. Actual time for inspiratory gas flow during PLV was shorter in PC mode compared with VC mode at both doses. In conclusion, in surfactant-depleted rabbit, gas exchange during PLV was better with PC mode compared with VC mode, especially at a low perfluorocarbon dose. Given the same tidal volume, PC appeared to insufflate the perfluorocarbon-filled lung better than VC at both low and FRC doses of perfluorocarbon.

Animals↗

PubMed2001

Effects of heat pretreatment on histopathology, cytokine production, and surfactant in endotoxin-induced acute lung injury.

To determine the effect of heat stress on histopathology of acute lung injury (ALI) caused by administration of lipopolysaccharide (LPS), and to determine the roles of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, interferon (IFN)-gamma, IL-10 and surfactants in heat-induced tolerance to ALI, we administered either saline or LPS (3 mg/kg of body weight) intravenously to male Sprague-Dawley rats without and with heat pretreatment. Five hours after LPS or saline treatment (23 h after heat-pretreatment), samples were obtained. We found that the histopathologic features of LPS-induced ALI were attenuated by heat-pretreatment. Heat-pretreatment did not decrease the elevated plasma or BAL fluid levels of TNF-alpha, IL-1beta, and IFN-gamma by LPS. The plasma level of IL-10 in LPS-treated rats with heat-pretreatment, however, was increased compared to that of LPS-treated rats without heat-pretreatment (P = 0.001). There were no differences in the BAL fluid concentrations of light or heavy density pulmonary surfactant phospholipids depending on heat-pretreatment in LPS-treated rats. These observations suggest that IL-10 might play a role in decreasing LPS-induced acute lung injury after heat-pretreatment.

Acute Disease↗

PubMed2001

Effect of increasing perfluorocarbon dose on VA/Q distribution during partial liquid ventilation in acute lung injury.

BACKGROUND: Although gas exchange during partial liquid ventilation (PLV) depends on perfluorocarbon liquid, the effect of perfluorocarbon dose on the ventilation-perfusion (VA/Q) distribution is not known. This study investigated how VA/Q distribution of an acutely injured lung is affected during PLV at increasing perfluorocarbon dose. METHODS: In eight rabbits (3.2 +/- 0.1 kg), acute lung injury (ALI) was created by repeated saline lavage (arterial oxygen partial pressure/fraction of inspired oxygen, 37 +/- 11 mm Hg). Three different doses of perfluorodecalin (9 ml/kg = low dose; 13.5 ml/kg = medium dose; 18 ml/kg = functional residual capacity [FRC] dose) were applied in random order during PLV. VA/Q distribution at different doses was evaluated by multiple inert gas elimination technique. RESULTS: Inert gas shunt (63 +/- 21% at ALI) decreased with increasing perfluorocarbon dose (43 +/- 21% at low dose, 29 +/- 10% at medium dose, 11 +/- 9% at FRC dose; P = 0.022). Compared with ALI (0%), the proportion of low VA/Q units was higher at all tested doses (19 +/- 10, 25 +/- 12, and 34 +/- 18%, respectively; all P < 0.05). Compared with ALI (27 +/- 14%), the proportion of normal VA/Q units was not increased at low or medium doses but was increased only at the FRC dose (45 +/- 13%; P = 0.027). CONCLUSIONS: With increasing perfluorocarbon dose during PLV, shunt was reduced from a small dose. The majority shunt units were converted to units showing low VA/Q ratios rather than normal VA/Q ratios. The presence of considerable amount of low VA/Q units across the varying doses of perfluorocarbon suggested that additional measures are necessary during PLV to augment its effect on gas exchange.

Animals↗

PubMed2001

Inhaled nitric oxide down-regulates intrapulmonary nitric oxide production in lipopolysaccharide-induced acute lung injury.

OBJECTIVE: To examine whether inhaled nitric oxide (NO) affected the intrapulmonary production of NO, reactive oxygen species, and nuclear factor-kappaB in a lipopolysaccharide (LPS)-induced model of acute lung injury. DESIGN: Prospective, randomized, laboratory study. SETTING: Experimental laboratory at a biomedical institute. SUBJECTS: Twenty male rabbits weighing 2.5-3.5 kg. INTERVENTIONS: Saline or LPS (5 mg/kg of body weight) was administered intravenously with or without NO inhalation (10 ppm) in each group of five rabbits. MEASUREMENTS AND MAIN RESULTS: LPS increased the lung leak index, the neutrophils and NO levels in bronchoalveolar lavage fluid, and NO levels produced by resting and stimulated alveolar macrophages. Inhaled NO decreased the lung leak index, the neutrophils and NO levels as measured by nitrite levels in the lavage fluid, and NO produced by the resting and stimulated alveolar macrophages. Inhaled NO also blocked the activities of reactive oxygen species and nuclear factor-kappaB binding to DNA in lavage cells and in alveolar macrophages. CONCLUSION: Inhaled NO attenuates LPS-induced acute lung injury, possibly by decreasing NO production in the lungs. The mechanism of reducing NO production resulting from inhaled NO may involve, in part, the activities of reactive oxygen species and/or nuclear factor-kappaB.

Acute Disease↗

PubMed2001

Mechanistic scheme and effect of "extended sigh" as a recruitment maneuver in patients with acute respiratory distress syndrome: a preliminary study.

OBJECTIVE: To devise a new form of sigh ("extended sigh") capable of providing a sufficient recruiting pressure x time, and to test it as a recruitment maneuver in patients with acute respiratory distress syndrome. DESIGN: Prospective uncontrolled clinical trial. SETTING: Medical intensive care unit of a university-affiliated hospital. PATIENTS: Twenty consecutive patients diagnosed with acute respiratory distress syndrome (18 men, 2 women, age 59 +/- 10 yrs). INTERVENTIONS: From baseline settings of tidal volume (Vt) 8 mL/kg and positive end-expiratory pressure (PEEP) 10 cm H2O on volume control mode with the high pressure limit at 40 cm H2O, the Vt-PEEP values were changed to 6-15, 4-20, and 2-25, each step being 30 secs (inflation phase). After Vt-PEEP 2-25, the mode was switched to continuous positive airway pressure of 30 cm H2O for a duration of 30 secs (pause), after which the baseline setting was resumed following the reverse sequence of inflation (deflation phase). This extended sigh was performed twice with 1 min of baseline ventilation between. MEASUREMENTS AND RESULTS: Airway pressures and hemodynamic parameters were traced at each step during the extended sigh. Arterial blood gases and physiologic parameters were determined before the extended sigh (pre-extended sigh), at 5 mins after two extended sighs (post-extended sigh), and then every 15 mins for 1 hr. In our average patient, the recruiting pressure x time of the inflation phase was estimated to be 32.8-35.4 cm H2O x 90 secs. Compared with the inflation phase, inspiratory pause pressure of the deflation phase was lower at Vt-PEEP 6-15 (28.9 +/- 2.7 cm H2O vs. 27.3 +/- 2.8 cm H2O) and 4-20 (31.8 +/- 2.9 cm H2O vs. 31.1 +/- 2.9 cm H2O; both p <.05). Compared with pre-extended sigh, Pao2 (81.5 +/- 15.3 mm Hg vs. 104.8 +/- 25.0 mm Hg; p <.001) and static respiratory compliance both increased post-extended sigh (27.9 +/- 7.9 mL/cm H2O vs. 30.2 +/- 9.7 mL/cm H2O; p =.009). Improvement in these parameters was sustained above pre-extended sigh for the duration of the study. Major hemodynamic or respiratory complications were not noted during the study. CONCLUSION: We present a new form of sigh (i.e., extended sigh) capable of achieving an augmented recruiting pressure x time through a prolonged inflation on a gradually increased end-expiratory pressure. In view of the sustained effect and absence of major complications in our patients, extended sigh could be a useful recruitment maneuver in acute respiratory distress syndrome.

Airway Resistance↗

PubMed2001

Cigarette smoke extract induces endothelin-1 via protein kinase C in pulmonary artery endothelial cells.

We examined the mechanism of endothelin (ET)-1 regulation by cigarette smoke extract (CSE) and the effect of platelets on CSE-induced stimulation of ET-1 gene expression in human and bovine pulmonary artery endothelial cells (PAECs). Our data show that CSE (1%) induces ET-1 gene expression (after 1 h) and ET-1 peptide synthesis (after 4 h) in bovine PAECs. The induction of preproET-1 mRNA level was due to de novo transcription, and new protein synthesis was not required for this induction. The protein kinase C inhibitors staurosporine (10(-8) mol/l) and calphostin C (10(-7) mol/l) abolished the induction of ET-1 gene expression by CSE in bovine and human PAECs. Although a lower concentration of platelets (10(6) cells/ml in bovine PAECs; 10(7) cells/ml in human PAECs) did not significantly alter ET-1 gene expression in PAECs, incubation of platelets with CSE (1%) and PAECs produced a significant increase in preproET-1 mRNA and ET-1 peptide compared with the values in the presence of CSE (1%) alone. CSE (1%) induced platelet aggregation and increased the expression of platelet membrane glycoproteins ex vivo. Thus our data suggest that CSE stimulates ET-1 gene expression via PKC in PAECs. CSE and platelets showed a synergistic effect on ET-1 gene expression, possibly through the activation of platelets by CSE.

Animals↗

PubMed2001

Lung cancer in patients with idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) was reported to be associated with increased risk of lung cancer as a result of the occurrence of atypical or dysplastic epithelial changes in fibrosis which progressed to invasive malignancy. In that situation, the cancer will develop in the area of major fibrosis. To investigate the direct relationship between fibrosis and cancer development, the real concordance rate of the two lesions in the chest computed tomography (CT) was analysed and compared to the histological types of lung cancer. The subjects included 63 patients with combined lung cancer and IPF (IPF-CA), 218 patients with lone IPF, and 2,660 patients with primary lung cancer. All patients were diagnosed at Asan Medical Center during the same period. The age, percentage of smokers, and the male sex were significantly higher in IPF-CA compared with lone IPF. The odds ratio of smoking was 2.71 compared to nonsmoking IPF controls. In IPF-CA, 56% of the cancer was located in the periphery of the lung and 52% in the upper lobe. The majority of the cancers (64%) were found in the nonfibrotic area at chest CT. The most frequent cell type was squamous cell carcinoma (35%), and there was no significant difference in the cancer cell type between IPF-CA and total lung cancer population. These findings suggest that in combined lung cancer and idiopathic pulmonary fibrosis patients, the features of the lung cancer are similar to the total lung cancer population.

Aged↗

PubMed2001

Nitric oxide and molsidomine in the management of pulmonary hypertension in Takayasu's arteritis.

We present three patients with pulmonary hypertension in Takayasu's arteritis who showed long-term favorable response, clinically and hemodynamically, to nitric oxide donor molsidomine. In these patients, nitric oxide inhalation was effective in reducing pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR). Molsidomine (single dose of 4 mg p.o.) was also effective in reducing PAP and PVR, but nifedipine was not. With molsidomine, 4 mg tid, dyspnea, exercise capacity, and hemodynamic parameters were improved. These favorable responses have lasted during the 3-month follow-up period in all patients.

Adult↗

PubMed2001

The prognosis of respiratory failure in patients with tuberculous destroyed lung.

SETTING: The medical intensive care unit of a tertiary referral hospital. OBJECTIVE: To determine the prognosis of patients whose lungs are damaged by previous and/or present tuberculosis infection and who have subsequently been presented with acute respiratory failure requiring mechanical ventilation. DESIGN: A consecutive series of 38 patient cases with retrospective data analysis. RESULTS: Pulmonary function test results for tests performed within the previous year were made available in 21 of the 38 cases (55%). These showed a mean (+/- SD) forced vital capacity (FVC) of 1.52 +/- 0.46 L (41.0 +/- 14.5% predicted), a forced expiratory volume/second (FEV1) of 0.77 +/- 0.18 L (29.3 +/- 13.6% predicted), and an FEV1/FVC ratio of 55.1 +/- 16.2%. The acid-fast bacilli (AFB) positive group had a significantly higher mortality and more severe lung destruction when compared with the AFB-negative group. Patients with positive AFB were significantly more hypocapnic than those with negative AFB (6.4 +/- 2.7 vs. 9.3 +/- 3.9 kPa, P = 0.020). In multivariate analysis, the level of PaCO2 on admission was identified as the only significant prognostic index (OR 0.76, 95%CI 0.60-0.96). CONCLUSION: Patients with positive AFB smears or cultures may have higher mortality rates than those with negative AFB in the tuberculosis destroyed lung patients with acute respiratory failure. A higher PaCO2 measurement could indicate a better survival rate in this group of patients.

Adult↗

PubMed2000

Multi-organ failure caused by reactivated coccidioidomycosis without dissemination in a patient with renal transplantation.

OBJECTIVE: The acute respiratory failure caused by pulmonary coccidioidomycosis without dissemination is an extremely unusual event. CASE REPORT: We report a 47-year-old renal transplanted man with a reactivated pulmonary coccidioidomycosis, whose clinical course presented as fulminant respiratory failure, disseminated intravascular coagulation and profound hypotension mimicking bacterial pneumonia and septic shock. Lung biopsy showed conglomerated necrotizing granulomas containing many spherules filled with endospores of Coccidioides immitis. CONCLUSION: Coccidioidomycosis should be included in the differential diagnosis of acute sepsis, particularly in an immunocompromised host who has travelled in an endemic area.

Coccidioidomycosis↗

PubMed2000

Effect of an additional 1-hour T-piece trial on weaning outcome at minimal pressure support.

PURPOSE: The purpose of this article was to investigate the effect of an additional 1-hour T-piece trial at the level of minimum pressure support (PSmin) on weaning outcome. MATERIALS AND METHODS: Open, randomized, prospective study of 44 patients who had received mechanical ventilation for more than 3 days.Thirty-six patients satisfied the protocol. There were 42 weaning trials. The patients were randomized into an intervention group (additional 1-hour period of T-piece trial) and a control group (extubation directly) at PSmin. Blood gas analysis and estimation of respiratory and hemodynamic variables were performed at the 15 cm H2O level of pressure support. Measurements were repeated at PSmin and during weaning process (in intervention group). RESULTS: Mean PSmin level was 7.6 (+/- 1.9) cm H2O. There were no differences in total ventilation time (TVT), acute physiology and chronic health evaluation (APACHE) II score, nutritional indices, and respiratory mechanics on PSmin between the two groups. The weaning success rate and the reintubation rate were similar for the intervention group (55% and 18%, respectively) and control group (70% and 20%, respectively). Work of breathing, pressure time product, and tidal volume significantly worsened after a 1-hour T-piece trial when compared with those values measured at PSmin in the intervention group (P < .05). For the combined patient sample, TVT and tidal volume at PSmin were significantly different between the patients with weaning success (246 +/- 195 hours, 0.43 +/- 0.11 L) and those with weaning failure (407 +/- 248 hours, 0.35 +/- 0.10 L) (P < .05 in each). CONCLUSION: There were no advantages in weaning outcome by the addition of a 1-hour T-piece trial compared with prompt extubation at PSmin.

APACHE↗