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Chih-Cheng Wu

Publications and source records attributed to Chih-Cheng Wu.

15 recordsLinked to original sources
PubMed2007

Aerosol penetration properties of an electret filter with submicron aerosols with various operating factors.

This study was undertaken to determine the effects of using an electret filter on aerosol penetration. Various factors, including particle size (0.05 to 0.5 micro m), aerosol charge state (neutral and single charge), face velocity (0.1, 0.3, 0.5 and 1.0 m/s), and relative humidity (RH 30% and RH 70%), were examined to assess their effects on aerosol collection characteristics. The results presented here demonstrate that the electric fields of the electret and discharged filter were -1.53 x 104 and -1.3 x 102 (V/m). The penetration through the electret filter with singly charged aerosol and neutral aerosol ranged from 0.4% to 13% and 14% to 29%, respectively. According to these results, the coulombic capture force was dominant for the smaller aerosol and the dielectrophoretic capture mechanism was considered important for the larger aerosol. The level of penetration through the electret filter increased with increasing face velocity and relative humidity. The temperature did not affect the penetration through the electret. Furthermore, from the regression analysis conducted during the operating conditions of this work, the aerosol charge was shown to exert the greatest influence on aerosol penetration.

Aerosols↗
PubMed2006

Effectiveness of photocatalytic filter for removing volatile organic compounds in the heating, ventilation, and air conditioning system.

Nowadays, the heating, ventilation, and air conditioning (HVAC) system has been an important facility for maintaining indoor air quality. However, the primary function of typical HVAC systems is to control the temperature and humidity of the supply air. Most indoor air pollutants, such as volatile organic compounds (VOCs), cannot be removed by typical HVAC systems. Thus, some air handling units for removing VOCs should be added in typical HVAC systems. Among all of the air cleaning techniques used to remove indoor VOCs, photocatalytic oxidation is an attractive alternative technique for indoor air purification and deodorization. The objective of this research is to investigate the VOC removal efficiency of the photocatalytic filter in a HVAC system. Toluene and formaldehyde were chosen as the target pollutants. The experiments were conducted in a stainless steel chamber equipped with a simplified HVAC system. A mechanical filter coated with Degussa P25 titania photocatalyst and two commercial photocatalytic filters were used as the photocatalytic filters in this simplified HVAC system. The total air change rates were controlled at 0.5, 0.75, 1, 1.25, and 1.5 hr(-1), and the relative humidity (RH) was controlled at 30%, 50%, and 70%. The ultraviolet lamp used was a 4-W, ultraviolet-C (central wavelength at 254 nm) strip light bulb. The first-order decay constant of toluene and formaldehyde found in this study ranged from 0.381 to 1.01 hr(-1) under different total air change rates, from 0.34 to 0.433 hr(-1) under different RH, and from 0.381 to 0.433 hr(-1) for different photocatalytic filters.

Air Conditioning↗
PubMed2005

Evaluation of cardiac function by tissue Doppler echocardiography: hemodynamic determinants and clinical application.

A total of 32 patients without regional wall motion abnormality of the left ventricle underwent sequential tissue Doppler echocardiography and cardiac catheterization. Peak velocities of systolic (Sa), early diastolic (Ea), and late diastolic (Aa) motion of the mitral annulus were measured. Normal references for Sa, Ea and Aa were obtained from 138 volunteers. Indices of left ventricular (LV) systolic and diastolic function were evaluated using high-fidelity LV pressure and volume signals. By multivariate analysis, Sa, Ea and As were significantly and independently related to the maximum of the first derivative of pressure over time (dP/dt(max)), LV relaxation time constant (tau), and LV ejection fraction (EF), respectively. Using the fifth percentiles of the age-stratified normal references as cut-offs, low Sa, low Ea and low Aa identified declined dP/dt(max), prolonged tau and reduced EF, respectively, with good sensitivities and specificities. In conclusion, mitral annulus velocities by tissue Doppler echocardiography can be used to identify patients with declined dP/dt(max), prolonged tau and reduced EF.

Adult↗
PubMed2005

Efficacy and safety of slow-release fluvastatin 80 mg daily in Chinese patients with hypercholesterolemia.

BACKGROUND: Before this study, the efficacy and safety of doubling the dosage of fluvastatin from 40 mg/day to 80 mg/day in Chinese patients with primary hypercholesterolemia remained to be determined. METHODS: In this open-label, active-controlled randomized 2-center study, patients with primary hypercholesterolemia were randomized to treatment with immediate-release fluvastatin 40 mg/day (n = 30) or slow-release fluvastatin 80 mg/day (n = 31) for 12 weeks. The primary efficacy variable was percent change in low-density lipoprotein (LDL) cholesterol level from baseline. Secondary efficacy variables were percent changes in total cholesterol, triglyceride, and high-density lipoprotein (HDL) cholesterol levels, and the percent of patients achieving LDL cholesterol goals of the US National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) II. RESULTS: Both fluvastatin dosages (40 mg/day vs 80 mg/day) effectively reduced LDL cholesterol (-22.5% vs -29.9%; p = 0.087), total cholesterol (-17.3% vs -22.5%; p = 0.140), and triglyceride levels (-14.0% vs -12.3%; p = 0.813) (all p < 0.0001 for comparison with baseline), and slightly increased HDL cholesterol levels (+5.2% vs +5.6%; p = 0.917), after 12 weeks of treatment. The percent of patients achieving LDL cholesterol goals of the NCEP ATP II was 37% versus 65% (p < 0.05). The adverse event profiles for the 2 fluvastatin dosages were similar. CONCLUSION: In Chinese patients with primary hypercholesterolemia, doubling the dosage of fluvastatin from 40 to 80 mg once daily was effective and safe regarding reduction of LDL cholesterol level, and allowed more patients to achieve LDL cholesterol goals of the NCEP ATP II.

Adult↗
PubMed2004

The assessment of fluid status in haemodialysis patients: usefulness of the Doppler echocardiographic parameters.

BACKGROUND: In end-stage renal disease (ESRD) patients undergoing regular haemodialysis (HD), the maintenance of fluid status within an optimal range is critical. We therefore examined the role of Doppler echocardiographic parameters in the assessment of fluid status in these patients. METHODS: Three study groups were enrolled: 40 healthy volunteers (NTNR), 40 HD patients who were normotensive without receiving antihypertensive agents (NTHD) and 38 HD patients who had remained hypertensive (HTHD) despite antihypertensive treatment. Measurements of Doppler echocardiographic parameters from pulmonary vein (PV) and mitral inflow (Mi) were performed on a non-dialysis day. Extracellular water as a percentage of body weight (ECW%) and pre-dialysis mean blood pressure (BDMBP) were references for fluid status. The best Doppler parameter for fluid status assessment identified from the study groups was then tested in another validation groups (38 NTHD and 38 HTHD). RESULTS: Among all of the PV and Mi parameters, the S/D ratio (peak systolic velocity divided by peak diastolic velocity) was correlated with fluid status parameters best (with ECW%, r = -0.49, P<0.001; with BDMBP, r = -0.51, P<0.001). The correlations were independent of age, sex and Mi parameters. The receiver operating characteristics curve analysis demonstrated that an S/D ratio >1.33 had a sensitivity of 90% and a specificity of 77% in identifying NTHD patients. When the same criterion was applied to the validation groups, the positive predictive value was 64% and the negative predictive value was 86%. CONCLUSION: The Doppler-derived S/D ratio is a potentially useful marker for the assessment of fluid status in HD patients.

Adult↗
PubMed2004

Cardiac catheterization-induced type-A aortic dissection detected by intra-operative transesophageal echocardiography--a case report.

Cardiac catheterization is not only a diagnostic tool but also a means of treatment of coronary artery disease. Coronary artery dissection is one of the complications of cardiac catheterization. Emergency coronary artery bypass graft (CABG) surgery is indicated when coronary artery dissection is associated with unstable perfusion or residual severe stenosis. We present a case of progressive type-A aortic dissection as a continuity of catheterization-induced dissection of right coronary artery (RCA) with occlusion, disclosed by transesophageal echocardiography (TEE) during the emergent CABG surgery for the iatrogenic injury. Once the aortic dissection has been diagnosed by TEE, the surgical procedure and cannulation site for cardiopulmonary bypass were altered from those used in regular CABG surgery. Therefore, TEE is able and valuable in such situation to detect this rare but severe complication due to catheterization, especially when retrograde coronary artery dissection has been noted preoperatively.

Aged↗
PubMed2003

Utility of patient-activated cardiac event recorders in the detection of cardiac arrhythmias.

BACKGROUND: Patient-activated event recorders are useful for the diagnosis of arrhythmia in patients with palpitation and presyncope. However, the utility of event recorders in patients suspected of arrhythmia but presenting with other symptoms is not clear. Furthermore, the factors influencing their utility have not been evaluated. METHODS: Event recorder reports of six hundred and sixty consecutive patients referred due to clinical suspicion of cardiac arrhythmia were reviewed. We divided symptoms into four groups: palpitation, presyncope, chest tightness, and dyspnea. We calculated the diagnostic yield according to patients' symptoms reported on the record, and analyzed the factors affecting the utility of event recorders. RESULTS: The overall diagnostic yield was 64%, and those of palpitation, presyncope, chest tightness, and dyspnea were 66%, 57%, 51% and 60%, respectively. The most common five findings in our patients were sinus rhythm (36%), sinus tachycardia (30%), atrial premature complex (14%), ventricular premature complex (12%), and atrial fibrillation/atrial flutter (7%). The recording duration (8 +/- 4 days) was short in the present study, but the overall diagnostic yield was similar to those of previous ones. Women had lower diagnostic yields than men, especially in atrial flutter-fibrillation. The diagnostic yield was not influenced by age, ordered doctors, or history of cardiovascular disease. CONCLUSIONS; Patient-activated event recorders provided a good diagnostic yield in patients with different presentations of cardiac arrhythmia, and women had lower diagnostic yield in atrial flutter-fibrillation.

Arrhythmias, Cardiac↗
PubMed2003

Impact of left ventricular function on the pulmonary vein Doppler spectrum: nonsimultaneous assessment with load-insensitive indices.

Pulmonary vein Doppler spectrum is highly load-dependent and thus has been used to estimate left ventricular (LV) filling pressure. However, the impact of LV function on pulmonary vein Doppler spectrum remains obscure because only load-sensitive indices were studied previously. In the present study, measurements of the pulmonary vein Doppler spectrum were correlated with load-insensitive LV systolic (end-systolic elastance [Ees]) and diastolic (relaxation time constant [tau] and beta coefficient of the end-diastolic pressure volume relationship) function indices obtained from an invasive catheterization study nonsimultaneously. The peak velocity, velocity time integral, and duration of systolic forward spectrum were significantly correlated with Ees (r = 0.35, r = 0.36, and r = 0.41, respectively;P < 0.05). The pulmonary vein diastolic velocity time integral (PVDVTI) and duration of the diastolic forward spectrum were significantly correlated with Ees (r = 0.51 and r = 0.57, respectively;P < 0.01). PVDVTI was correlated with tau and the end-diastolic pressure-volume relationship (EDPVR) (r = 0.42 and r = 0.40 respectively,P < 0.05). On the other hand, the systolic fraction of the forward spectrum was significantly correlated with ejection fraction (for peak velocity,r = 0.63, P < 0.01; for velocity time integral,r = 0.37, P < 0.05) but not with Ees, and the diastolic fraction of the forward spectrum was significantly correlated with minimum pressure derivative over time (for peak velocity,r = 0.48, P < 0.05; for velocity time integral,r = 0.44, P < 0.05, respectively) but not with tau or EDPVR. In summary, the systolic and diastolic components of the pulmonary vein Doppler spectrum are affected variably by LV systolic and diastolic function, independent of the loading condition. The systolic and diastolic fraction of pulmonary vein Doppler spectrum appears to depend more on the loading condition than the LV systolic or diastolic function.

Aged↗
PubMed2002

Assessment of left ventricular end-systolic elastance from aortic pressure-left ventricular volume relations.

The left ventricular (LV) end-systolic pressure-volume relation (ESPVR) is a load-insensitive method for evaluating LV contractility, which needs invasive measurement. Some noninvasive methods substitute peak aortic pressure (Ps) for end-systolic LV pressure by assuming there is no difference between these pressures. However, this assumption has not been directly validated. With conductance catheter and dual micromanometers, ESPVRs and the slope (EesLv) were constructed from simultaneous LV pressures (LVP) and volumes, aortic pressures (AOP) and LV volumes (Ees(AO)), and Ps and LV end-ejection volumes (VEE) (Ees(PP-EEV)) during preload reduction in 50 subjects. The ratio of steady-state P(s) over V(EE) (P(S)/V(EE)) was also checked. AOP and LVP displayed differences of 11 +/- 6 and -30 +/- 12 mm Hg at the onset and end-ejection, respectively, and -2 +/- 4 mm Hg at end-systole. Ees(AO) and Ees(LV) were nearly identical: Ees(AO) = 0.97 x Ees(LV) + 0.05, r2 = 0.99. Ees(PP-EEV) correlated with EesLV (EesPP-EEV = 0.57 x EesLV + 0.61, r2 = 0.46) but with much more scatter. Ps/V(EE) correlated worst with Ees(LV). Central AOP can be substituted for LVP to derive EesLV. Other estimation methods yield weaker and poor correlations to directly measured Ees.

Aorta↗
PubMed2002

Intraoperative aortic dissection--a case report.

Intraoperative aortic dissection is a rare but potentially fatal complication of cardiac surgery. Prompt recognition and repair are necessary to limit the extent of dissection to minimize morbidity and mortality. Here, we present a case of acute type A dissection of ascending aortic artery occurring after removal of aortic cannula at the end of cardiopulmonary bypass. The surgeon immediately recannulated him at the femoral artery and repaired the dissection under deep hypothermia. Ascending aorta was replaced with Hemashield graft and venous graft was reimplanted. Unfortunately, the patient expired the following day due to cardiac tamponade resulting from uncontrolled bleeding. Long-standing severe hypertension, severe atherosclerotic change of the aortic wall, thin and dilating ascending aorta and cystic medial necrosis or collagen vascular disease were thought to predispose him to this complication. Gentle manipulation and surgical discreetness to forestall aoratic injury could minimize the risk of intraoperative aortic dissection. Once aortic dissection has been suspected, prompt application of transesophageal echocardiography to confirm the diagnosis, and rapid as well as appropriate surgical management are necessary to grasp a better outcome.

Aged↗
PubMed2002

Contralateral neurologic deficits following microvascular decompression surgery--a case report.

Microvascular decompression (MVD) surgery for trigeminal neuralgia (Jannetta operation) is common in our institution, and postoperative complications are uncommon. However, a 46 year-old obese female who underwent MVD surgery for right trigeminal neuralgia suffered from postoperative neurologic deficits consisting of left facial palsy, left total deafness, weakness and numbness of the left arm, and unsteady gait. Here, we bring forth the patient's postoperative events, such as delayed emergence, postoperative convulsions, pneumocephalus, and probable causes of the neurologic deficits for discussion.

Deafness↗
PubMed2002

Metastatic hepatocellular carcinoma of the right atrium causing right ventricular outflow tract obstruction during induction of anesthesia--a case report.

Metastatic hepatocellular carcinoma (HCC) to the right atrium occurs rarely and may lead to lethal perioperative complications. A 61-year-old female who was about to undergo operation for resection of a right intraatrial tumor thought possibly to be metastatic hepatocellular carcinoma met with sudden protrusion of the tumor from the right atrial wall that sank into the right ventricle during induction of anesthesia. Right ventricular outflow tract obstruction developed and was quickly diagnosed by transesophageal echocardiography. Emergent cardiopulmonary bypass was rushed on the spot and the surgery was completed smoothly. Here we discuss the possible causes of the event and we recommend that special attention should be paid to the anesthetic techniques and proper precaution should be taken in the face of such a risky surgery.

Anesthesia↗
PubMed2002

Endotracheal tube fire induced by electrocautery during tracheostomy--a case report.

Airway fire resulting from ignition of the endotracheal tube (ETT) caused by electrocautery during tracheostomy is a severe and possibly fatal event, and should be avoided. An 88-year-old male because of respiratory failure received elective tracheostomy for ventilatory support on which prolonged dependence was anticipated. Unfortunately, flame was noted to jet out from the trachea incision just after a single burst of electrocautery to coagulate a bleeder in the trachea tissue nearby the incision. After primary management, including extinguishing the flame and evaluation of the tracheal injury by bronchoscope, a tracheostomy tube was inserted smoothly without causing hypoxemia or hemodynamic instability. The patient stood this ordeal of fire well without related sequelae and was returned from the intensive care unit (ICU) to the general ward two weeks later. From this accident, we recommend that, besides emphasis on lowering of the inspired oxygen concentration (FiO2) and careful use of electrocautery during the tracheostomy procedure, special attention should be paid to the integrality of ETT cuff. It serves as a barrier to prevent oxygen leaking out from the trachea to be exposed to the sparks of electrocautery while the surgical procedure is under way, and thus it plays a significant role in the avoidance of airway fire induced by electrocautery.

Aged↗