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PubMed1993

Enteral nutrition with simultaneous gastric decompression in critically ill patients.

OBJECTIVE: Early enteral nutrition is an important adjunct in the care of critically ill patients. A double-lumen gastrostomy tube with a duodenal extension has been reported to enable early enteral feeding with simultaneous gastroduodenal decompression. We tested the ability of this device to achieve these goals in critically ill patients. DESIGN: Noncomparative, descriptive case series. SETTING: Surgical intensive care unit in a university hospital. PATIENTS: Fifteen consecutive critically ill patients, who, at the time of laparotomy, were assessed likely to need long-term nutritional support and gastric decompression, underwent tube placement. Mean age was 47 +/- 21 yrs. Mean Acute Physiology and Chronic Health Evaluation (APACHE II) and Therapeutic Intervention Scores were 15 +/- 7.3 (SD) and 29 +/- 10.2, respectively, and the mean Injury Severity Score of 11 trauma patients in the group was 27 +/- 7.4. INTERVENTIONS: Correct tube positioning was verified by radiograph or endoscopy. METHODS: Caloric and protein requirements, nutritional parameters, and problems encountered with the device were recorded. The correlation between the volume of feeding port input and suction port output was noted, and this correlation was considered significant if r2 was > or = .5. RESULTS: Only three (20%) of 15 patients reached full enteral nutritional support via the enteral route. None of these patients achieved this level of nutritional support within the first postoperative week. In 67% of the patients, large quantities of enteral feeding solution appeared in the gastroduodenal suction port effluent. When feeding port input was plotted against effluent volume, a correlation coefficient of > .71 (r2 = > or = .5) was found in 40% of the patients. Other complications included: a) excessive gastroduodenal drainage requiring fluid/electrolyte replacement in eight (53.3%) patients; and b) skin ulceration at the tube entrance site in seven (46.7%) patients. CONCLUSIONS: These data do not support the use of this device for early enteral feeding and simultaneous gastric decompression in critically ill patients.

Adolescent↗
PubMed1998

Diffusive vs. convective therapy: effects on mediators of inflammation in patient with severe systemic inflammatory response syndrome.

OBJECTIVE: To compare two forms of continuous renal replacement therapy, continuous venovenous hemofiltration (CVVH) vs. continuous venovenous hemodialysis (CVVHD), in terms of the removal of inflammatory mediators from the blood of patients with systemic inflammatory response syndrome and acute renal failure. DESIGN: Randomized crossover, clinical study. SETTING: University teaching hospital. PATIENTS: Thirteen patients with systemic inflammatory response syndrome and acute renal failure receiving continuous renal replacement therapy. INTERVENTION: Patients were randomized to receive either convective clearance using CVVH or diffusive clearance using CVVHD for the first 24 hrs, followed by the other modality for 24 hrs. All treatments utilized AN69 hemofilters. CVVH was performed with an ultrafiltration rate of 2 L/hr and CVVHD with a dialysis outflow rate of 2 L/hr. MEASUREMENTS AND MAIN RESULTS: Plasma and ultrafiltrate concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-10, and sL-selectin were measured at 0, 1, 3, 6, 12, and 24 hrs by radioimmunoassay. Plasma endotoxin concentrations were also measured at 0, 12, and 24 hrs by chromogenic assay. CVVH was associated with a 13% decrease in plasma TNF-alpha concentrations compared with a 23% increase while on CVVHD (p < .05). Mean plasma concentrations of IL-6, IL-10, and sL-selectin were unchanged over time and between therapies. Only minimal amounts of mediators were recovered in the effluents with either therapy except for IL-6. The clearances for IL-6 were different between therapies, 1.9+/-0.8 (SD) mL/min for CVVHD and 3.3+/-1.5 mL/min for CVVH, (p< .01). Plasma endotoxin concentrations were not different between therapies. CONCLUSION: CVVH resulted in a decrease in plasma TNF-alpha concentrations as compared with CVVHD, while the type of transport mechanism used did not influence plasma concentrations of IL-6, IL-10, soluble L-selectin, or endotoxin. Differences in clearance for IL-6 between CVVH and CVVHD did not translate into significant changes in circulating IL-6 concentrations.

Acute Kidney Injury↗
PubMedDate not supplied

High-performance liquid chromatography (HPLC) determination of inosine, a potential biomarker for initial cardiac ischaemia, using isolated mouse hearts.

Each year in the USA approximately 7-8 million patients with non-traumatic chest pain come to hospital emergency rooms. It is estimated that approximately 2-5% of these patients are experiencing cardiac ischaemia, but due to the shortcomings of the available testing methods they are incorrectly diagnosed and discharged without appropriate therapy having been provided. Preliminary data with a globally ischaemic mouse heart model has demonstrated that endogenous inosine might be a potential biomarker of initial cardiac ischaemia before cardiac tissue necrosis. A high-performance liquid chromatographic diode array detection (HPLC-DAD) method was utilized for the detection and quantification of inosine in Krebs-Henseleit (Krebs) buffer solution perfusing from surgically removed and isolated mouse hearts undergoing global cardiac ischaemia. A C18 column at a flow rate of 0.6 ml min-1 with an aqueous mobile phase of trifluoroacetic acid (0.05% trifluoroacetic acid in deionized water, pH 2.2, v/v) and methanol gradient was used for component separation. The assay detection limit for inosine in Krebs buffer solution was 500 ng ml-1 using a 100-microl neat injection. The HPLC results were used to determine total cardiac effluxed inosine into the Krebs effluent for each mouse during oxidative stress and compared with the per cent cardiac ventricular functional recovery rate to determine if a relationship exists amongst this cardiovascular parameter during periods of cardiac oxidative stress.

Animals↗
PubMed1993

The optimal glucose concentration for intermittent cardioplegia in isolated rat heart when added to St. Thomas' Hospital cardioplegic solution.

The purpose of this study was to determine the mechanisms by which high physiologic concentrations of glucose (11 mmol/L) were protective while even higher concentrations (20 or 50 mmol/L) were harmful when added to St. Thomas' Hospital No. 2 cardioplegic solution. We evaluated the recovery of isolated working rat hearts subjected to 3 hours of hypothermic multidose cardioplegic arrest. The addition of glucose 11 mmol/L was associated with better aortic flow (79.2% +/- 1.3%) than the addition of glucose 1 mmol/L (61.7% +/- 2.7%), 20 mmol/L (73.6% +/- 1.1%), or 50 mmol/L (66.0% +/- 3.2%) (p < 0.01 versus glucose 1 and 50 mmol/L). An increase in glucose concentration from 1 to 50 mmol/L progressively augmented glucose flux from 2.2 +/- 0.33 to 10.4 +/- 0.79 mumol/gm per 3 hours (p < 0.01), but higher glucose concentrations of 20 and 50 mmol/L inhibited glycogenolysis (p < 0.05 versus glucose 1 and 11 mmol/L), so that total glycolysis was decreased and consequently glycolytic adenosine triphosphate production was reduced from 35.9 +/- 0.47 (glucose 11 mmol/L) to 27.5 +/- 1.25 mumol/gm per 3 hours (glucose 50 mmol/L) (p < 0.01). The end products of glycolysis (lactate and protons) did not appear to affect the recovery of the hearts, because both lactate efflux and tissue lactate were highest in the presence of glucose 11 mmol/L and the pH of the cardioplegic effluent was more alkalotic in glucose 11 and 20 mmol/L. Thus a high physiologic concentration of glucose (11 mmol/L) in the cardioplegic solution improved recovery because of an increased glycolytic adenosine triphosphate production during cardioplegic arrest, whereas even higher concentrations of glucose inhibited these effects.

Adenosine Triphosphate↗
PubMed1979

Penetration of gown material by organisms from the surgical team.

The routes by which viable organisms shed by the surgical team reach the wound are not yet fully understood. Bacteriologic studies show that shedding is greater in surgeons than their assistants or scrub nurses, and is increased by activity and temperature, but is primarily related to the individual's shedding characteristics. Comparison of the ability of 3 types of cotton gowns to contain the surgical team's bacterial effluent shows that the body exhaust system gowns developed by Charnley are superior to more conventional gowns. It is clear that viable organisms can penetrate very closely woven Ventile (pore size 10 microns) as well as balloon cloth (pore size 50 microns). Ventile used without a body exhaust system does not appear to increase gown efficiency. Penetration of gown material by organisms from the surgical team is responsible for 20% of wound contamination. The gown glove cuff junction is an important leakage point for organisms shed by the surgical team. A newly designed "mitt" cuff more effectively seals this area than the conventional stockinette cuff.

Clothing↗
PubMed1997

[The temperature dependency of the protective properties of the St. Thomas' Hospital cardioplegic solution, the University of Wisconsin solution, and Bretschneider buffered solution].

We studied three preservation solutions such as St. Thomas' hospital cardioplegic solution No. 2 (ST), the University of Wisconsin solution (UW) and Bretschneider's solution (BR) for protective properties, especially in terms of temperature dependence during the preservation. Rat hearts were studied and divided into three groups; ST. UW and BR. In each group, six hearts were carried out perfusion, cardioplegic infusion, ischemia and reperfusion for four different conditions. Using an isolated working rat heart model, the hearts were subjected to 5 minutes Langendorff perfusion followed by 20 minutes working perfusion. During this working period, cardiac functions such as aortic and coronary flow, aortic pressure, and heart rates were measured every 5 minutes. After working perfusion, 3 minutes of cardioplegic infusion was carried out either with UW, ST, and BR at 37, 20, 4, 1 degree C. The hearts were subjected to either 35 min at 37 degrees C, 120 min at 20 degrees C, 300 min at 4 degrees C, or 450 min at 1 degree C. The hearts were immersed in the same solution during ischemia. The hearts were reperfused at 37 degrees C, initially in the Langendorff mode for 15 min. Coronary effluent was collected for the measurement of CK leakage during reperfusion. The heart were then converted to the working mode for 20 minutes. During working reperfusion period, the variables of cardiac function were again measured and expressed as a percentage of their individual preischemic control values. Under conditions of 37 degrees C ischemia, % recovery of cardiac output (%CO) in ST group is 62.8 +/- 2.8%, although the hearts preserved with UW and BR were not recovered. Under conditions of 20 degrees C ischemia, %CO in UW, ST and BR were 46.8 +/- 2.7, 82.0 +/- 3.1 and 41.4 +/- 2.6%, respectively. Under conditions of 4 degrees C ischemia, %CO in UW, ST and BR were 66.2 +/- 8.0, 68.6 +/- 2.3 and 47.2 +/- 2.9%, respectively. Under conditions of 1 degrees C ischemia, %CO in UW, ST and BR were 70.6 +/- 3.3, 56.5 +/- 1.6 and 43.0 +/- 2.5%, respectively. In conclusions, ST revealed the best protective properties for the heart preservation between 37 degrees C and 20 degrees C ischemia. The properties of ST was similar to that of UW under conditions of 4 degrees C, although UW showed most excellent protective properties under conditions of 1 degrees C ischemia. These results suggested that, protective ability of preservation solution might be changed by the temperature during preservation period.

Adenosine↗
PubMed2003

Comparison of discharge silver concentrations from electrolytic plating and metallic replacement silver recovery units.

Silver-based photographic X-ray film is made of solid crystals of silver chloride or silver bromide suspended in a gelatin and then coated on a film. During the X-ray developing process, the image is processed and the nonimage areas containing solid silver chloride or silver bromide crystals are removed in a solution called the fixer. There may be local environmental regulations that regulate the amount of silver discharged from a facility. To meet these regulations, many facilities have added silver recovery units to their processes. Two different types of recovery processes are in use in a large hospital and three clinics under study. All of the units were claimed by their respective manufacturers to be able to recover silver down to concentrations of 5 mg/L. This concentration would ensure that the building that houses each unit would meet the local county limit of 0.5 mg/L silver for total building silver discharge. The hypothesis for this research is that one system, newer and more expensive, consisting of so-called electrolytic plating units (EPUs) (which are followed by so-called metallic replacement units [MRUs] as a backup), will have better silver recovery than MRUs alone. A total of six units were sampled, three EPUs (in combination with MRUs) and three MRUs. The units were sampled once or twice a day for 10 days for a total of 17 samples from each. The samples then were analyzed by inductively coupled plasma spectroscopy, and an analysis of variance was performed on the results. The range for the electrolytic plating unit/metallic replacement unit combinations was 0.20-99.9 mg/L (mean of 35.15 mg/L; median of 33.8 mg/L). The range for the MRUs alone was 7.2-1112 mg/L (mean of 565.5 mg/L; median of 720 mg/L). Many individual results exceeded 5 mg/L, such that extensive dilution would be required to ensure the building effluent did not exceed 0.5 mg/L. It is suggested that the metallic replacement units be changed to EPUs (with metallic replacement backup units) because they had better silver recovery. Also, the EPU combinations need to be sampled regularly to ensure that their silver concentrations are at acceptable levels.

Conservation of Natural Resources↗
PubMed2003

A formula for prediction of posttraumatic pneumonia based on early anatomic and physiologic parameters.

BACKGROUND: Identification of risks for development of ventilator-associated pneumonia (VAP), which might be identified early after injury, would allow for prognostic estimates and targeting of high-risk cohorts for clinical trials of preventive strategies. This study was performed to develop an equation that can be applied to estimate the probability of pneumonia based on parameters collected in the early postinjury interval. METHODS: Over a 28-month period, patient admissions were reviewed for mechanism and severity of injury, patterns of injury, shock, and need for emergent intubation. Early deaths (<48 hours) were excluded. VAP diagnosis required > or = 10(5) colony-forming units/mL organisms in the bronchoalveolar lavage effluent. Multiple logistic regression analysis was used to develop the prediction equation and estimate odds ratios. The equation was then tested on consecutive patients admitted over a 2-month period. RESULTS: We reviewed 9,721 admissions (77% blunt, 23% penetrating). VAP incidence was 5.6%. Overall mortality was 2% (21% for patients with VAP vs. 1% for no VAP; p < 0.0001). Multiple logistic regression analysis for all patients produced the following equation: f(x) = -3.08 - 1.56 (MOI) - 0.12 (GCS) + 1.37 (SCI) + 0.30 (chest AIS) + 1.87 (lap) + 0.67 (tx) + 0.05 (ISS) + 0.66 (int), where MOI is mechanism of injury (penetrating = 1, blunt = 0), GCS is Glasgow Coma Scale score, SCI is spinal cord injury (yes = 1, no = 0), lap is emergent laparotomy (yes = 1, no = 0), ISS is Injury Severity Score, tx is units of blood transfused in the resuscitation room, and int is intubation in either the field or the resuscitation room (yes = 1, no = 0). The probability of VAP was calculated as follows: P(VAP) = e(f)(x)/1 + e(f)(x). This formula was concordant in 95% and discordant in 5%. CONCLUSION: It is possible to accurately predict risk for VAP in trauma patients based on data available early after injury. This calculation could be useful for counseling families relative to prognosis and research protocols, and addressing hospitalization issues with third-party payors.

Adult↗
PubMedDate not supplied

Peritoneal dialysis in children with spina bifida and ventriculoperitoneal shunt: one center's experience and review of the literature.

OBJECTIVE: The goal of this paper was to review the viability of peritoneal dialysis (PD) in patients with spina bifida and/or ventriculoperitoneal shunt (VPS). SETTING: Pediatric dialysis unit in a tertiary-care hospital. DATA SOURCE: The course and outcome in 9 children, 5 from the authors' experience and 4 from reported experience, are analyzed. RESULTS: One patient died of a cause unrelated to PD or VPS, 2 were transferred to hemodialysis because of recurrent peritonitis, 1 discontinued PD transiently, 2 were transplanted, and 3 continue on PD. Six of these 9 children had a functioning VPS, and none presented evidence of ventriculitis or VPS dysfunction, even though 4 had PD-related peritonitis. One child presented with a massive PD-related hydrothorax. CONCLUSIONS: (1) Having a VPS is not an absolute contraindication to PD; the available data support the viability of PD in patients with spina bifida and/or a VPS. (2) If cerebrospinal fluid diversion is needed simultaneously or after starting PD, an extraperitoneal site should be a better choice than VPS. This should avoid the risk of intra- and postoperative infection in the PD catheter secondary to surgical intervention for VPS insertion. (3) Loss of peritoneal function is a potential late risk related to cerebrospinal fluid and PD. (4) Spina bifida patients on PD present specific diagnostic challenges due to overlapping symptoms (e.g., vomiting, abdominal tenderness, fever) secondary to PD- or VPS-related complications (e.g., peritonitis, visceral injury by devices) or primary disease (e.g., neurogenic bladder, pyelonephritis), with inherent risks of delaying adequate treatment. Cloudy peritoneal effluent is an early indication of peritonitis, although it is not specific. (5) Early evaluation by a pediatric surgeon and a neurosurgeon is required for effective management of complications and selection of more efficient individualized therapeutic alternatives. Prompt treatment of complications is crucial. A registry of children with spina bifida on PD and the accumulation of a large population followed up for longer periods will provide an objective assessment of their problems and management.

Adolescent↗
PubMedDate not supplied

Risk factors responsible for ultrafiltration failure in early stages of peritoneal dialysis.

OBJECTIVE: To define risk factors for ultrafiltration failure (UFF) during early stages of peritoneal dialysis (PD). DESIGN: Retrospective analysis of a group of patients whose peritoneal function was prospectively followed. SETTING: A tertiary-care public university hospital. PATIENTS: Nineteen of 90 long-term PD patients required a peritoneal resting period to recover UF capacity: 8 had this requirement before the third year on PD (early, EUFF group) and 11 had a late requirement (LUFF group). The remaining 71 patients, those with stable peritoneal function over time, constituted the control group. MAIN OUTCOME MEASURES: Peritoneal UF capacity under standard conditions (monthly) and small solute peritoneal transport (yearly). RESULTS: None of the conditions appearing at the start of PD or during the observation period could be definitely identified as the cause of UFF. There were no differences in characteristics between the EUFF group and the other two groups, except for the higher prevalence of diabetes in the EUFF group. Residual renal function (RRF) declined in all three groups during the first 2 years, with rapid loss during the third year in the EUFF group. This rapid loss in RRF was coincident with UFF. Peritoneal solute and water transport at baseline was similar in the three groups. After 2 years on PD, individuals in the EUFF group showed a significantly lower UF and higher creatinine mass transfer coefficient values than those in the LUFF group. Diabetic patients in the control group showed remarkable stability in UF capacity over time. During the second year on PD, requirement for increases in dialysate glucose concentration was 3.4 +/- 0.5% in the LUFF group, but as high as 25.5 +/- 24.2% in the EUFF group. The accumulated days of active peritonitis (APID, days with cloudy effluent) were similar for the three groups after 1, 2, and 3 years on PD. Interestingly, diabetic patients in the control group showed an APID index significantly lower than the overall EUFF group. Diabetics in the control group also had significantly lower APID versus nondiabetics in the control group (p = 0.016). CONCLUSIONS: Our findings suggest that certain patients develop early UFF type I. Diabetic state and a higher glucose requirement to obtain adequate UF suggest that glucose on both sides of the peritoneal membrane could be responsible. The mechanisms for this higher requirement remain to be elucidated. The identification of a larger cohort of these early UFF patients should lead to a better exploration of the primary pathogenic mechanisms.

Hemodiafiltration↗
PubMed2004

The appropriate diagnostic threshold for ventilator-associated pneumonia using quantitative cultures.

BACKGROUND: The use of quantitative cultures of the bronchoalveolar lavage (BAL) effluent to distinguish between posttraumatic inflammatory response and ventilator-associated pneumonia (VAP) is becoming more common. However, the diagnostic threshold of either 10 or 10 colonies/mL remains debatable. Because mortality from VAP is related to treatment delay, some have chosen a lower diagnostic threshold (>10 colonies/mL). This may result in unnecessary antibiotic use with its sequelae: increased resistant organisms, antibiotic-related complications, and increased costs. The purpose of this study is to determine the optimal diagnostic threshold for VAP diagnosis using quantitative cultures of the BAL effluent. METHODS: Data on patients with fiberoptic bronchoscopy with BAL are maintained in a prospectively collected database at our Level I trauma center. This database was reviewed for timing and frequency of BAL and the colony counts of each organism identified. Indication for bronchoscopy was clinical evidence of VAP. VAP was defined as >10 colonies/mL in the BAL effluent. A false-negative BAL was defined as any patient who had <10 colonies/mL and developed VAP with the same organism up to 7 days after the previous culture. RESULTS: Over a 46-month period, 526 patients underwent 1,372 fiberoptic bronchoscopy procedures with BAL. Of these, 72% were male patients, 91% followed blunt injury, and mean age and Injury Severity Score were 43 years and 30, respectively. Overall mortality was 14%. There were 1,898 organisms identified (42% were gram-positive and 58% were gram-negative). VAP was diagnosed in 38% of BAL. Overall, there were 43 episodes in 38 patients defined as false-negative (3%). The false-negative rate was 9% in patients with 10 organisms. The most common false-negative organisms were Pseudomonas and Acinetobacter species. CONCLUSION: The VAP diagnostic threshold for quantitative BAL in trauma patients should be >10 colonies/mL. One may consider a threshold of >10 colonies/mL in severely injured patients with Pseudomonas or Acinetobacter species.

Adult↗
PubMed1986

Bacterial colonization of ultrasonic nebulizers: implications for frequency of circuit changing.

UNLABELLED: We conducted a prospective study of 50 consecutive postoperative patients over a 5-month period to characterize the bacterial contamination of ultrasonic nebulizers (USNs) after 24, 48, and 72 hours (h) of use. METHODS: Samples of the USN effluent mist and reservoir fluid were cultured and the results were correlated with clinical data from patient records, especially indications of pneumonia or related infections. RESULTS: Two thirds of the USNs were bacteria-free at the three times they were tested. After 24 h, cultures of the mist revealed bacterial growth in only 1 of the 50 patients. After 48 and 72 h, cultures of the mist showed bacterial growth in 6 instances (12%). Colonization of the reservoir fluid was also limited to 1 patient after 24 h. Reservoir-fluid cultures were positive in 10% of the USNs at 48 h and in 18% at 72 h. No clinically significant signs of pneumonia developed in any patient. CONCLUSIONS: These results suggest that colonization of USNs is minimal during the first 72 h of use by postoperative patients with uncomplicated clinical courses and that clinical consequences are unlikely in such patients even when the USN is found to have been colonized. Although the Centers for Disease Control has recommended daily changing of USN circuits, this practice may not be warranted in all clinical settings. Further studies are needed to determine the colonization of USNs used by patients with more complicated clinical courses.

Connecticut↗
PubMed2002

Polynuclear aromatic hydrocarbon and particulate emissions from two-stage combustion of polystyrene: the effects of the secondary furnace (afterburner) temperature and soot filtration.

Laboratory experiments were conducted in a two-stage horizontal muffle furnace in order to monitor emissions from batch combustion of polystyrene (PS) and identify conditions that minimize them. PS is a dominant component of municipal and hospital waste streams. Bench-scale combustion of small samples (0.5 g) of shredded styrofoam cups was conducted in air, using an electrically heated horizontal muffle furnace, kept at Tgas = 1000 degrees C. Upon devolatilization, combustion of the polymer took place in a diffusion flame over the sample. The gaseous combustion products were mixed with additional air in a venturi and were channeled to a secondary muffle furnace (afterburner) kept at Tgas = 900-1100 degrees C; residence time therein varied between 0.6 and 0.8 s. At the exits of the primary and the secondary furnace the emissions of CO, CO2, O2, NOx, particulates as well as volatile and semivolatile hydrocarbons, such as polycyclic aromatic hydrocarbons (PAH), were monitored. Online analyzers, gravimetric techniques, and gas chromatography coupled to mass spectrometry (GC-MS) were used. Experiments were also conducted with a high-temperature barrier filter, placed just before the exit of the primary furnace to prevent the particulates from entering into the secondary furnace. Results demonstrated the beneficial effect of the afterburner in reducing PAH concentrations, including those of mutagenic species such as benzo[a]pyrene. Concentrations of individual PAH exhibited a pronounced after burner temperature dependence, typically ranging from a small decrease at 900 degrees C to a larger degree of consumption at 1100 degrees C. Consumption of PAH was observed to be the dominant feature at 900 degrees C, while significant quantities of benzene and some of its derivatives, captured by means of carbosieve/Carbotrap adsorbents, were formed in the afterburner at a temperature of 1000 degrees C. In the primary furnace, about 30% of the mass of the initial polystyrene was converted into soot, while the total mass of PAH represented about 3% of the initial mass of combustible. The afterburner reduced the particulate (soot) emissions by only 20-30%, which indicates that once soot is formed its destruction is rather difficult because its oxidation kinetics are slow undertypical furnace conditions. Moreover, increasing the afterburnertemperature resulted in an increasing trend of soot emissions therefrom, which might indicate competition between soot oxidation and formation, with some additional formation occurring at the higher temperatures. Contrary to the limited effect of the afterburner, high-temperature filtration of the combustion effluent prior to the exit of the primary furnace allowed for effective soot oxidation inside of the ceramic filter. Filtration drastically reduced soot emissions, by more than 90%. Limited soot formation in the afterburner was again observed with increasing temperatures. The yields of both CO and CO2 were largely unaffected by the temperature of the afterburner but increased at the presence of the filter indicating oxidation therein. A previously developed kinetic model was used to identify major chemical reaction pathways involving PAH in the afterburner. The experimental data at the exit of the primary furnace was used as input to these model computations. A first evaluation of the predictive capability of the model was conducted for the case with ceramic filter and a temperature of 900 degrees C. The afterburner was approximated as a plug-flow reactor, and model predictions at a residence time of 0.8 s were compared to experimental data collected at its exit. In agreement with the experimental PAH concentration, only a minor impact of the afterburner treatment was observed for most species at 900 degrees C. OH was deduced to be the major reactant with a mole fraction about 4 orders of magnitudes higher than that of hydrogen radicals. Evidence for the need of further work on the quantitative assessment of oxidation of PAH and their radicals is given.

Air Pollutants↗