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Biomedical subjects

D P Chang

Publications and source records attributed to D P Chang.

10 recordsLinked to original sources
PubMed1995

[The effect of needleless electroacupuncture in general anesthesia during laparoscopic surgery].

BACKGROUND: Three kinds of pain-relieving substances, namely, endorphins, enkephalins and dynorphins, can be released by stimulating the relevant acupoints with the dense-disperse mode of nerve stimulator. The neurochemical mechanisms of pain relief by acupoint stimulation have been widely studied and proved. In the present study, we investigated the modulatory effect of needleless electroacupuncture on the inhaled general anesthesia during laparoscopic surgery. METHODS: Forty gynecologic patients of ASA class I-II status, scheduled for elective laparoscopic surgery, were randomly allocated to study and control groups. Induction and intubation were performed in the same fashion and anesthesia was maintained with inhaled general anesthetics: 50% N2O in oxygen and isoflurane, which was adjusted to keep the hemodynamic changes within +/- 10% of their preoperated level. HANS (LY 257), a special nerve stimulator with 2 Hz and 100 Hz dense-disperse wave, was used to stimulate the bilateral Yang Ling Chuan (G34), Zusanli (S36) acupoints in patients of the study group during the surgery. RESULTS: We found that needleless electroacupuncture significantly lowered the volume concentration of isoflurane from 1.0 +/- 0.33% to 0.74 +/- 0.19% (p < 0.05) at 30 min after the start of operation. Furthermore, it also significantly shortened the recovery time from 11.4 +/- 3.3 min to 8.8 +/- 3.2 min (p < 0.05). CONCLUSIONS: Under general anesthesia, the application of needleless electroacupuncture can reduce the volume concentration of isoflurane and shorten the post-anesthetic recovery time during laparoscopic surgery.

Adult↗
PubMed1994

An inversion algorithm for determining area-source emissions from downwind concentration measurements.

Measuring emissions from nonuniform area sources, such as waste repository sites, has been a difficult problem. A simple but reliable method is not available. An objective method of inverting downwind concentration measurements, utilizing an assumed form of atmospheric dispersion to reconstruct total emission rate and distribution, is described in this study. The Gaussian dispersion model is compared to a more realistic model based on K-theory and similarity expressions. A sensitivity analysis is presented indicating the atmospheric conditions under which a successful application of the method could be anticipated. Field releases of sulfur hexafluoride (SF6) from a simulated area source in flat terrain were conducted to check the method, ability to reconstruct source distribution, and total emission rate. The sensitivity analysis and the field study confirm that a few ground-level concentration measurements and a simple determination of the atmospheric dispersion characteristics are sufficient, under neutral to stable conditions, to obtain the total emission rate accurately. Reconstruction of the spatial pattern of the source is possible by utilizing concentration information from samplers located on two separate ground-level receptor lines, if a shift in the wind direction occurs and if it can be assumed that the total emission rate is time invariant. A method of cross-checking the accuracy of the reconstruction, using a simultaneous tracer release, is presented.

Air Pollutants, Occupational↗
PubMed1994

The effect of heated humidifier in the prevention of intra-operative hypothermia.

Unintentional hypothermia is common in patients undergoing "routine anesthesia in surgery". The aims of the study were to estimate the difference of changes of body temperature during abdominal and limb operations and to evaluate the effectiveness of the heated humidifier for reducing intraoperative heat loss. Forty-three patients were randomly being allocated into 3 groups. Group I consisted of 14 patients undergoing abdominal operation without the use of heated humidifier. Another 22 patients were being assigned as group II to have a heated humidifier on the inspiratory limb of the breathing circuit. The inspired gas was warmed to 39 degrees C and the relative humidity was 90%. 7 patients undergoing limb operation were attributed to group III without using heated humidifier to humidify and warm up the inspired gas. For body temperature monitoring, the probe was placed on the patient's nasopharynx and the temperature was measured immediately before induction of anesthesia, post-intubation, and then once again every 15 minutes up to 3 hours after induction. All patients in the 3 groups showed a rapid decrease of body temperature in the first hour and then the hypothermic change was slow down. The lowest level of body temperature was reached at about 2 hours after induction. Patients undergoing abdominal operation decreased body temperature greater than those undergoing limb operation for about 2 degrees C after 3 hours of anesthesia and surgery. Warming and humidifying the inspired gas effectively reduced the heat loss. We concluded that abdominal operation induce hypothermia more than limb operation. The use of heated humidifier was effective in maintaining body temperature.

Adult↗
PubMed1991

An equilibrium analysis of some chlorinated hydrocarbons in stoichiometric to fuel-rich post-flame combustion environments.

The equilibrium composition of product gases from the combustion of chlorinated hydrocarbons (CHC) has been studied for varying ratios of C, H, Cl, and O under stoichiometric to fuel-rich conditions. An interactive, PC-compatible FORTRAN program, STANJAN, was utilized in conjunction with thermochemical data sources to calculate equilibrium compositions of gas mixtures as a function of temperature. The predicted results, when judiciously interpreted, assist in the understanding of the potential for formation of residual organic substance emissions (ROSEs) in post-flame environments of an incinerator. Arguments are presented for the potential formation of chlorinated species, which are stable at ambient temperature, if locally fuel-rich mixtures penetrate into the lower temperature zones of an incinerator. ROSEs that have been observed in field tests of incinerators burning chlorinated compounds are predicted to form under the fuel-rich condition. Furthermore, when the equivalence ratio is greater than unity by even a slight amount, the degree of chlorination of product gases increases markedly when the Cl/H ratio also exceeds unity. In that case, time, temperature, turbulence and an overall fuel-lean stoichiometry may not be sufficient to guarantee elimination of measurable levels of chlorinated products. Possible implications of the equilibrium calculations are discussed. Further systematic studies with additional CHCs, nitrogen-, sulfur-, and heavy metal-bearing compounds are recommended as well as continued efforts to carry out kinetic studies.

Air Pollutants, Occupational↗
PubMed1991

An analysis of biomedical waste incineration.

The California Air Resources Board (ARB) completed a series of source tests of eight operating biomedical waste incinerators (BMWI) under conditions of typical operation. The emissions of certain metals, and chlorinated dioxins and furans in the flue gases of BMWI are relatively high in comparison to emissions from other combustion sources, such as hazardous waste or municipal waste incinerators of modern design. This study reports on an analysis of the status of the existing regulatory framework and the California data base. Clarification of definitional issues at the federal level is needed to effectively treat BMWI management issues. Although few relationships among combustion parameters and emissions were uncovered, patterns of emissions were evident, suggesting commonality and relationships among the waste stream constituents and emissions. Potential implications for future research, operation of BMWI, controls and source reduction and waste segregation strategies are also discussed.

Medical Waste↗
PubMed1987

A computer-assisted image-analysis system for analyzing polymorphonuclear leukocyte chemotaxis in patients with diabetes mellitus.

A computer-assisted image-analysis system that precisely tracks the cell movements of up to 50 polymorphonuclear leukocytes (PMNLs) was developed and used to quantitatively measure cellular chemokinesis and chemotaxis in normal individuals and in diabetic patients with hyperglycemia. The PMNLs were tested in Zigmond chambers with or without a gradient of 10(-7) M n-formylmethionylleucylphenylalanine (f-Met-Leu-Phe). Cellular movement was recorded on videotape by using a videocamera mounted on the microscope. The videotapes were analyzed by computer programs to calculate the speed and direction of each PMNL at 10-sec intervals. Average rates of chemokinesis were 19.6 microns/min without and 25.3 microns/min with f-Met-Leu-Phe. McCutcheon indices, which measure chemotaxis, were 0.01 without and 0.48 with f-Met-Leu-Phe. Similar values were observed in diabetic patients after fasting (average glucose, 217 mg/100 ml) and 2 hr after glucose challenge (average glucose, 309 mg/100 ml). These values demonstrate that PMNLs from diabetic patients with hyperglycemia move at normal rates and respond appropriately to f-Met-Leu-Phe.

Adolescent↗
PubMed1984

A mechanism of synergistic lung damage by ozone and a respirable aerosol.

A hitherto unexpected synergism between the oxidant air pollutants ozone or nitrogen dioxide and a respirable-sized aerosol of ammonium sulfate was previously observed during controlled exposures of rats to these substances. In this paper we examine biochemical and morphometric changes in lungs of rats exposed for 3, 7, or 14 days to ozone (0.64-0.96 ppm), with or without an accompanying aerosol (approximately 1 micrometer mass median aerodynamic diameter) of ammonium sulfate (5 mg/m3). After 3 days of exposure to the mixture of pollutants, rat lung macrophage and macrophage precursors (monocytes) were increased 2- to 3-fold, fibroblasts were increased 2-fold, and apparent collagen synthesis rates were increased 2.5-fold, fibroblasts were increased 2-fold, and apparent collagen synthesis rates were increased 2.5-fold, as compared with values from animals exposed to ozone alone. Continued exposure to ozone alone for 7 or 14 days seemed to mimic changes seen at 3 days with the mixture of pollutants. Total number of lesions per lung was the same for ozone exposure with and without accompanying aerosol; lesions were larger in lungs of rats exposed to ozone plus ammonium sulfate. Based on these findings and a review of the literature, a mechanism for ozone-aerosol synergism is proposed. We suggest that the lifetime of free radicals arising from interaction of oxidants such as ozone or nitrogen dioxide with molecules within the lung is increased by either local pH changes or changes in the local sulfate concentration (or both) caused by inhalation of the respirable aerosol.

Aerosols↗
PubMed1977

Experience with a high output sulfuric acid aerosol generator.

Experience with a high output sulfuric acid aerosol generator suitable for large chamber exposure studies is described. Sulfuric acid aerosol is produced by combining sulfur trioxide (SO3)(g) vapor with water vapor in the exposure chamber air supply. The mass output of the generator is stable over long periods, and the mass median aerodynamic diameter of the aerosol produced is in the submicron size range (0.3-0.6 micrometer).

Aerosols↗