Model-based identification of PEEP titrations during different volemic levels

A cardiovascular system (CVS) model has previously been validated in simulated cardiac and circulatory disease states. It has also been shown to accurately capture all main hemodynamic trends in a porcine model of pulmonary embolism. In this research, a slightly extended CVS model and parameter identification process are presented and validated in a porcine experiment of positive end-expiratory pressure (PEEP) titrations at different volemic levels. The model is extended to more physiologically represent the separation of venous and arterial circulation. Errors for the identified model are within 5% when re-simulated and compared to clinical data. All identified parameter trends match clinically expected changes. This work represents another clinical validation of the underlying fundamental CVS model, and the methods and approach of using them for cardiovascular diagnosis in critical care.

Analysis of expression data: an overview

After providing a brief introduction to microarray chips and experimental details, this overview discusses analysis techniques. Data analysis from microarray experiments generally involves two parts: acquiring and normalizing the data, and interpreting it. This unit focuses mostly on the latter, as it is less technology-specific.

Analysis of expression data: an overview

After providing a brief introduction to microarray chips and experimental details, this overview discusses analysis techniques. Data analysis from microarray experiments generally involves two parts: acquiring and normalizing the data, and interpreting it. This unit focuses mostly on the latter, as it is less technology-specific.

Set up of a serum-free culture system for bovine embryos: embryo development and quality before and after transient transfer

It is well known that serum in culture medium negatively affects blastocyst quality. The objective of this work was to develop and test a serum-free culture medium which could improve embryo quality, measured by the resistance to freezing, lipid and glutathione content of the resulting blastocysts, as well as the ability of the blastocysts to elongate after transient transfer to recipient cows. In a first experiment we showed that adding a mixture of insulin, transferrin and selenium to serum-free Synthetic Oviduct Fluid medium (SOF-ITS) improved embryo development and quality. In the second experiment, the addition of BSA to SOF-ITS further improved blastocyst development. Moreover, a reduction in lipid content of morulae was observed in SOF-ITS-BSA by comparison with morulae cultured with serum (SOF-FCS). The resistance to freezing measured by hatching rates 24h post-thawing was also improved for blastocysts with a diameter between 160 and 180 microm cultured in SOF-ITS-BSA by comparison to those produced with serum. In order to evaluate the redox potential of the embryos, reduced glutathione content (GSH) was evaluated both before and after cryopreservation. A significant decrease in glutathione was observed after freezing, whatever the culture medium, but no difference was observed between culture conditions. Transient transfers were performed and elongated D-13 embryos were recovered. Elongation was more pronounced and the embryonic disk more often visible in embryos cultured in SOF-ITS-BSA than in embryos cultured with FCS. In conclusion, the serum-free system we developed to produce in vitro bovine embryos meets the developmental and qualitative requirements for a large-scale use.

Dental plaque control effect of a zinc citrate dentifrice

OBJECTIVE

This research evaluated the antiplaque efficacy of a new 2% zinc citrate fluoride dentifrice versus a non-zinc matching placebo or a commercial fluoride dentifrice, also used as the washout product in two crossover studies.

METHODS

Healthy human subjects meeting inclusion criteria entered two respective randomized crossover clinical studies. Study 1 had 24 subjects, and compared the zinc dentifrice to the commercial fluoride dentifrice over a 24-hour period. Study 2 had 19 subjects, and compared the zinc dentifrice to the matching placebo over a 24-hour period. After one week of washout using the commercial fluoride dentifrice, the subjects used the test product for one week prior to the test period. Both studies employed the Modified Gingival Margin Plaque Index (MGMPI) for the assessments.

RESULTS

In Study 1, the mean differences in the MGMPI score, representing post-treatment plaque regrowth along the gingival margin for the zinc prototype as compared to the commercial fluoride dentifrice, were 13.87 (+/- 8.27) and 21.23 (+/- 11.08), respectively. Study 2 demonstrated the mean differences in MGMPI scores for the zinc dentifrice and a matching placebo of 14.99 (+/- 13.32) and 24.38 (+/- 7.69), respectively. In both studies, the zinc dentifrice demonstrated a significant 35% and 39% inhibition of dental plaque formation compared to those of their respective control dentifrices.

CONCLUSION

Two clinical studies demonstrated plaque control efficacy for a new zinc citrate-containing dentifrice, suggesting a new antiplaque and possible multi-benefit dentifrice for oral hygiene.

Energy and migratory behavior in glass eels (Anguilla anguilla)

The influence of energy content of glass eels (Anguilla anguilla) on their migratory behavior was investigated in November 2004 and February 2005 under laboratory conditions. Fish were sorted according to their response to a decrease in light intensity: Glass eels becoming active at dusk and using water flow to move with the current were considered as "active", whereas those remaining in the substratum throughout the catching period (24 h) were categorized as "inactive". "Active" glass eels exhibited higher energy content than "inactive" ones, whatever the catching month, and were more pigmented. Differences in percentage dry weight between "active" and "inactive" fish were already significant in the first pigmentary stages, suggesting that energy content plays a causal role in the estuarine migration of glass eels. The possible impact of energy state on the development of different migratory tactics in glass eels is discussed.

Comparison between Principal Component Analysis and Independent Component Analysis in Electroencephalograms Modelling

Principal Component Analysis (PCA) is a classical technique in statistical data analysis, feature extraction and data reduction, aiming at explaining observed signals as a linear combination of orthogonal principal components. Independent Component Analysis (ICA) is a technique of array processing and data analysis, aiming at recovering unobserved signals or 'sources' from observed mixtures, exploiting only the assumption of mutual independence between the signals. The separation of the sources by ICA has great potential in applications such as the separation of sound signals (like voices mixed in simultaneous multiple records, for example), in telecommunication or in the treatment of medical signals. However, ICA is not yet often used by statisticians. In this paper, we shall present ICA in a statistical framework and compare this method with PCA for electroencephalograms (EEG) analysis. We shall see that ICA provides a more useful data representation than PCA, for instance, for the representation of a particular characteristic of the EEG named event-related potential (ERP).

Does a positive end-expiratory pressure-induced reduction in stroke volume indicate preload responsiveness? An experimental study

BACKGROUND

Increases in positive end-expiratory pressure (PEEP) are often associated with cardiovascular depression, responding to fluid loading. Therefore, we hypothesized that if stroke volume (SV) is reduced by an increase in PEEP this reduction is an indicator of hypovolemia or preload responsiveness, i.e. that SV would increase by fluid administration at zero end-expiratory pressure (ZEEP). The relationship between the cardiovascular response to different PEEP levels and fluid load as well as the relation between change in SV as a result of change in preload (Frank-Starling relationship) were evaluated in a porcine model. In addition, other measures of fluid status were assessed.

METHODS

Eight, 20-22 kg, anesthetized, mechanically ventilated pigs were subjected to 0, 10, and 20 cm H(2)O PEEP at 10% (of estimated blood volume) hypovolemia, normo- and 10% hypervolemia, and to ZEEP at 20% hypervolemia. SV, cardiac output, intrathoracic blood volume and airway, esophageal, vascular pressures, stroke volume variations, left ventricular end-diastolic and end-systolic areas and respiratory variations in the diameter of the inferior vena cava were obtained.

RESULTS

At hypovolemia and normovolemia, 10 cm H(2)O PEEP induced a significant decrease in SV, while no change occurred at 10% hypervolemia. SV measured at ZEEP increased from hypovolemia to normovolemia and 10% hypervolemia, while no change was found between 10% and 20% hypervolemia. The sensitivity and specificity decrease in SV by PEEP indicating an increase in SV by fluids was 60-88% and 67%, respectively, depending on the volemic (preload) levels.

CONCLUSION

Although the overall results suggest that a change in SV by PEEP might predict preload responsiveness, the individual response of SV by 10 cm H(2)O PEEP and of the successive fluid administration seemed to be dependent on where on the Frank-Starling curve the heart function was located.

Epidemiology, clinical and laboratory characteristics of Staphylococcus aureus bacteraemia in a university hospital in UK

There has been a persistent increase in the number of meticillin-resistant Staphylococcus aureus (MRSA) and meticillin-susceptible Staphylococcus aureus (MSSA) bacteraemia in the UK. This prospective study included 147 episodes of S. aureus bacteraemia in 139 patients over a 14 month period, from 1 November 2001 to 31 December 2002. Eighty-seven (59%) episodes in 84 patients and 60 (41%) in 56 patients were due to MRSA and MSSA, respectively. An intra-vascular device (29, 33%) and a soft-tissue (15, 25%) source were the commonest identifiable foci for bacteraemia in the MRSA and MSSA groups, respectively. Attributable mortality in the MRSA group was higher than the MSSA group (33% vs 16%; P=0.03) but there was no statistical difference for either attributable (P=0.35) or crude (P=0.39) mortality between the two groups, when adjusted for age, respiratory focus and inappropriate antibiotic therapy. A respiratory source (P=0.02) and inappropriate antibiotic therapy (P=0.02) were associated with attributable mortality in the MRSA group whereas advanced age was the only risk factor (P=0.02) in the MSSA group. The present study shows that S. aureus bacteraemia continues to be a serious infection mostly affecting the elderly and emphasizes the need for improved strategy in the control and management of this condition.

Identification, characterization and quantitation of pyrogenic polycylic aromatic hydrocarbons and other organic compounds in tire fire products

On 15 August 2001, a tire fire took place at the Pneu Lavoie Facility in Gatineau, Quebec, in which 4000 to 6000 new and recycled tires were stored along with other potentially hazardous materials. Comprehensive gas chromatography-mass spectrometry (GC-MS) analyses were performed on the tire fire samples to facilitate detailed chemical composition characterization of toxic polycyclic aromatic hydrocarbons (PAHs) and other organic compounds in samples. It is found that significant amounts of PAHs, particularly the high-ring-number PAHs, were generated during the fire. In total, 165 PAH compounds including 13 isomers of molecular weight (MW) 302, 10 isomers of MW 278, 10 isomers of MW 276, 7 isomers of MW 252, 7 isomers of MW 228, and 8 isomers of MW 216 PAHs were positively identified in the tire fire wipe samples for the first time. Numerous S-, O-, and N-containing PAH compounds were also detected. The identification and characterization of the PAH isomers was mainly based on: (1) a positive match of mass spectral data of the PAH isomers with the NIST authentic mass spectra database; (2) a positive match of the GC retention indices (I) of PAHs with authentic standards and with those reported in the literature; (3) agreement of the PAH elution order with the NIST (US National Institute of Standards and Technology) Standard Reference Material 1597 for complex mixture of PAHs from coal tar; (4) a positive match of the distribution patterns of PAH isomers in the SIM mode between the tire fire samples and the NIST Standard Reference Materials and well-characterized reference oils. Quantitation of target PAHs was done on the GC-MS in the selected ion monitoring (SIM) mode using the internal standard method. The relative response factors (RRF) for target PAHs were obtained from analyses of authentic PAH standard compounds. Alkylated PAH homologues were quantitated using straight baseline integration of each level of alkylation.

An outbreak of Serratia marcescens on the neonatal unit: a tale of two clones

Serratia spp. are an important cause of hospital-acquired infections and outbreaks in high-risk settings. Twenty-one patients were infected or colonized over a nine-month period during 2001-2002 on a neonatal unit. Twenty-two isolates collected were examined for antibiotic susceptibility, beta-lactamase production and genotype. Random-amplified polymorphic DNA polymerase chain reaction and pulsed-field gel electrophoresis revealed that two clones were present. The first clone caused invasive clinical infection in four babies, and was subsequently replaced by a non-invasive clone that affected 14 babies. Phenotypically, the two strains also differed in their prodigiosin production; the first strain was non-pigmented whereas the second strain displayed pink-red pigmentation. Clinical features suggested a difference in their pathogenicity. No environmental source was found. The outbreak terminated following enhanced compliance with infection control measures and a change of antibiotic policy. Although S. marcescens continued to be isolated occasionally for another five months of follow-up, these were sporadic isolates with distinct molecular typing patterns.

Infection risk associated with a closed luer access device

The potential for microbial contamination associated with a recently developed needleless closed luer access device (CLAD) (Q-Syte; Becton Dickinson, Sandy, UT, USA) was evaluated in vitro. Compression seals of 50 multiply activated Q-Syte devices were inoculated with Staphylococcus epidermidis NCTC 9865 in 25% (v/v) human blood and then disinfected with 70% (v/v) isopropyl alcohol followed by flushing with 0.9% (w/v) sterile saline. Forty-eight of 50 (96%) saline flushes passed through devices that had been activated up to a maximum of 70 times remained sterile. A further 25 Q-Syte CLADs that had undergone multiple activations were challenged with prefilled 0.9% (w/v) sterile saline syringes, the external luer tips of which had been inoculated with S. epidermidis NCTC 9865 prior to accessing the devices. None of the devices that had been accessed up to 70 times allowed passage of micro-organisms, despite challenge micro-organisms being detected on both the syringe tip after activation and the compression seals before decontamination. These findings suggest that the Q-Syte CLAD may be activated up to 70 times with no increased risk of microbial contamination within the fluid pathway. The device may also offer protection from the external surface of syringe tips contaminated with micro-organisms.

Inter-patient variability upon induction with sevoflurane estimated by the time to reach predefined end-points of depth of anaesthesia

BACKGROUND AND OBJECTIVES

A difficult issue in anaesthesia is its titration for an individual patient to avoid over- and underdosage. Common practice is to use an initial dose and increase it subsequently if the defined end-point is not reached. This assumes that the end-point is reached after a similar interval of time in all patients given a similar dose. In order to test this hypothesis we measured the time to reach end-points such as loss of consciousness (LOC), a bispectral index (BIS) value of 60, the minimal BIS and the minimal mean arterial pressure (MAP) values.

METHODS

Thirty patients aged 18-60 yr scheduled for general surgery were included in this observational study. After preoxygenation, induction was performed with 6% inspired concentration of sevoflurane in 6 Lmin-1 oxygen using the SiBI connector and the tidal volume technique. Remifentanil was administered when the BIS value was 60 and tracheal intubation was performed 4 min later.

RESULTS

Time (median, minimum-maximum) to LOC, a BIS value of 60, the minimal BIS and MAP values were, respectively, 75 (45-135), 120 (75-270), 300 (120-720) and 450 (120-1200) seconds. The time to the minimal BIS value was significantly (P < 0.05) shorter than the time to reach the minimal MAP value.

CONCLUSIONS

These results demonstrate large inter-patient variability for the time necessary to reach defined end-points of depth of anaesthesia when a similar dose of anaesthetic is given. Measuring the time to reach a predefined BIS value would allow application of nociceptive stimuli only at adequate levels of hypnosis and would facilitate titration.

161 LIPID CONTENT, RESISTANCE TO CRYOPRESERVATION, AND SEX RATIO OF IN VITRO BOVINE BLASTOCYSTS PRODUCED IN A SERUM-FREE SYSTEM

In vitro-produced (IVP) bovine blastocysts are known to be more sensitive to cryopreservation than their in vivo counterparts. Removing serum from the culture medium decreases sanitary risk and could improve embryo resistance to cryopreservation by preventing the accumulation of intracellular lipids. Our objectives were to evaluate the lipid content, resistance to cryopreservation, and sex ratio of IVP embryos cultured in a serum-free system. Oocytes from slaughterhouse ovaries were matured in a serum-free enriched medium (Donnay et al. 2004 Reprod. Fertil. Dev. 16, 274) and cultured in 5% O2 in modified SOF supplemented with 5% FCS (FCS) or with insulin-transferrin-selenium (ITS) and 0.1 mg/mL polyvinylpyrrolidone (PVP) (ITS-PVP) or 4 mg/mL BSA (ITS-BSA) (Daniaux et al. 2005 Reprod. Fertil. Dev. 17, 217). Day 5 morulae were stained with the fluorescent dye Nile Red in order to evaluate their lipid content (Genicot et al. 2005 Theriogenology 63, 1181). Day 7 blastocysts (diameter ≥160 µm) were selected, classified according to their size, and frozen in HEPES-SOF containing 1.5 M ethylene glycol, 0.1 M sucrose, and 1.8 mg/mL wheat peptones (George et al. 2002 Reproduction 29, 51). The lipid content was significantly lower in morulae cultured in ITS-BSA compared with the two other media (320 ± 10 arbitrary fluorescence units vs. 383 ± 12 in FCS and 406 ± 10 in ITS-PVP; n = 271; ANOVA2: P < 0.01). After cryopreservation, a higher total hatching rate was found 24 h post-thawing in blastocysts cultured in ITS-BSA and for both serum-free conditions at 48 h (Table 1). In particular, embryos ≤180 µm cultured in FCS were less resistant to cryopreservation than embryos of the same size produced without serum. Expanded blastocysts cultured in ITS-BSA were sexed by PCR (Grisart et al. 1995 Theriogenology 43, 1097) and a higher proportion of male embryos was found (62.7%; n = 51). In conclusion, a complete serum-free system was set up from oocyte maturation to embryo cryopreservation that gave high quality embryos resistant to cryo-preservation. Embryos produced in ITS-BSA presented a lower lipid content, but a shift of the expanded blastocyst sex ratio toward males was observed. Table 1. Hatching rates post-thawing as a function of the blastocyst size and the culture medium

Evaluation of a 2% chlorhexidine gluconate in 70% isopropyl alcohol skin disinfectant

The efficacy of a new skin disinfectant, 2% (w/v) chlorhexidine gluconate (CHG) in 70% (v/v) isopropyl alcohol (IPA) (ChloraPrep), was compared with five commonly used skin disinfectants against Staphylococcus epidermidis RP62A in the presence or absence of protein, utilizing quantitative time-kill suspension and carrier tests. All six disinfectants [70% (v/v) IPA, 0.5% (w/v) aqueous CHG, 2% (w/v) aqueous CHG, 0.5% (w/v) CHG in 70% (v/v) IPA and 10% (w/v) aqueous povidone iodine (PI)] achieved a log(10) reduction factor of 5, in colony-forming units/mL, in a suspension test (exposure time 30s) in the presence and absence of 10% human serum. Subsequent challenges of S. epidermidis RP62A in a biofilm (with and without human serum) demonstrated reduced bactericidal activity. Overall, the most effective skin disinfectants tested against S. epidermidis RP62A were 2% (w/v) CHG in 70% IPA and 10% (w/v) PI. These results suggest that enhanced skin antisepsis may be achieved with 2% (w/v) CHG in 70% (v/v) IPA compared with the three commonly used CHG preparations [0.5% (w/v) aqueous CHG, 2% (w/v) aqueous CHG and 0.5% (w/v) CHG in 70% (v/v) IPA].

Effects of oligofructose on glucose and lipid metabolism in patients with nonalcoholic steatohepatitis: results of a pilot study

OBJECTIVE

In experimental animals, recent results suggest that the addition of inulin-type fructans such as oligofructose (OFS) in the diet decreases triacylglycerol accumulation in the liver tissue. Therefore, we have investigated the effect of daily ingestion of OFS in seven patients with nonalcoholic steatohepatitis (NASH), confirmed by liver biopsies.

DESIGN

They received 16 g/day OFS or maltodextrine (placebo) for 8 weeks in a randomized double-blind crossover design. Energy intake, body composition, liver steatosis and blood parameters were analysed after 4 and 8 weeks of dietary supplementation.

RESULTS

Compared to placebo, OFS decreased significantly serum aminotransferases, aspartate aminotransferase after 8 weeks, and insulin level after 4 weeks, but this could not be related to significant effect on plasma lipids.

CONCLUSION

This pilot study supports the putative interest of OFS in the management of liver diseases associated with abnormal lipid accumulation in humans.

Expression of the HPV16E7 oncoprotein by thymic epithelium is accompanied by disrupted T cell maturation and a failure of the thymus to involute with age

Transgenic mice expressing the E7 protein of HPV16 from the keratin 14 promoter demonstrate increasing thymic hypertrophy with age. This hypertrophy is associated with increased absolute numbers of all thymocyte types, and with increased cortical and medullary cellularity. In the thymic medulla, increased compartmentalization of the major thymic stromal cell types and expansion of thymic epithelial cell population is observed. Neither an increased rate of immature thymocyte division nor a decreased rate of immature thymocyte death was able to account for the observed hypertrophy.

Thymocytes with reduced levels of expression of CD4 and/or CD8 were more abundant in transgenic (tg) mice and became increasingly more so with age. These thymic SP and DP populations with reduced levels of CD4 and/or CD8 markers had a lower rate of apoptosis in the tg than in the non-tg mice. The rate of export of mature thymocytes to peripheral lymphoid organs was less in tg animals relative to the pool of available mature cells, particularly for the increasingly abundant CD4^lo population. We therefore suggest that mature thymocytes that would normally die in the thymus gradually accumulated in E7 transgenic animals, perhaps as a consequence of exposure to a hypertrophied E7-expressing thymic epithelium or to factors secreted by this expanded thymic stromal cell population. The K14E7 transgenic mouse thus provides a unique model to study effects of the thymic epithelial cell compartment on thymus development and involution.

Analogues of virus resistance genes map to QTLs for resistance to sharka disease in Prunus davidiana

Plum pox virus (PPV), the causative agent of sharka disease in Prunoideae, is one of the most serious problems affecting stone fruit production in Europe and America. Resistance to PPV was previously described in a Prunus davidiana clone, P1908, and introduced into peach (Prunus persica) genotypes. Genetic resistance to PPV displays a complex pattern of quantitative inheritance. An analysis of quantitative trait loci (QTLs) for resistance was performed on an F1 interspecific peach population obtained from a cross between the susceptible nectarine cultivar Summergrand and P. davidiana. The hybrids were graft-inoculated with PPV in duplicate following a classical procedure. The incidence of infection was evaluated four times, over two vegetative cycles, by symptom observation and enzyme-linked immunoadsorbent assays (ELISA). Restriction of systemic downward movement of the PPV virus was also evaluated by testing the susceptible rootstocks. Using both analysis of variance and non-parametric tests, six genomic regions involved in PPV resistance were detected. Depending on the scoring data considered, between 22 and 51% of the phenotypic variance could be explained by the quantitative model. One QTL, located in the distal region of linkage group 1, maps in a genomic region that is syntenic to the location of a resistance gene previously identified in the apricot cv. Goldrich. Some QTLs appeared to be temporally specific, reflecting the environmental dependence of PPV-resistance scoring. Candidate gene fragments were amplified by PCR, isolated and mapped on the peach interspecific linkage map. We report here the co-localization of three analogues of virus resistance genes with two distinct genomic regions linked to PPV resistance in P. davidiana.

Surprising sun: a new step towards a complete picture?

Important revisions of the solar model ingredients have appeared recently. We first show that the updated CNO composition suppresses the anomalous position of the Sun in the known galactic enrichment. The following law, He/H = 0.075 + 44.6 O/H in number fraction, is now compatible with all the indicators. We then suggest some directions of investigation to solve the discrepancies between the standard model and solar seismic observations. We finally update our predicted neutrino fluxes using a seismic model and all the recent progress. We get 5.31 +/- 0.6 x 10(6)/cm2/s for the total 8B neutrinos, 66.5 +/- 4.4 SNU and 2.76 +/- 0.4 SNU for the gallium and chlorine detectors, all in remarkable agreement with the detected values including neutrino oscillations for the last two. So, the acoustic modes and detected neutrinos see the same Sun, but the standard model fails to reproduce them.

Hypoxaemia after cardiac surgery: clinical application of a model of pulmonary gas exchange

BACKGROUND AND OBJECTIVE

To investigate the clinical application of a mathematical model of pulmonary gas exchange, which ascribes hypoxaemia to shunt and ventilation/perfusion mismatch. Ventilation/perfusion mismatch is quantified by deltaPO2, which is the drop in oxygen pressure from alveoli to lung capillaries. Shunt and deltaPO2 were used to describe changes in oxygenation after coronary artery bypass grafting.

METHODS

Fourteen patients were studied 2-4 h after surgery and on postoperative days 2, 3 and 7. On each occasion inspired oxygen fraction was changed in four to six steps to obtain arterial oxygen saturation (SaO2) in the range of 90-100%, enabling construction of FEO2/SaO2 curves. Measurements of ventilation, circulation and oxygenation were entered in a previously described mathematical model of pulmonary gas exchange.

RESULTS

We found that oxygenation was most impaired 3 days after surgery. By fitting the mathematical model to the FEO2/SaO2 curve, we found that shunt remained constant throughout the study period. However, deltaPO2 increased from 0.5 kPa (median, range 0-3.8) 2-4 h after surgery, to 3.2 kPa (range 1.2-6.4, P < 0.05) on day 2, and to 4.0 kPa (range 1.2-8.3) on day 3. On day 7, deltaPO2 decreased to 2.2 kPa (range 0-3.5, P < 0.05).

CONCLUSIONS

Ventilation/perfusion mismatch (deltaPO2), rather than shunt, explains the changes in postoperative oxygenation. The model of pulmonary gas exchange may serve as a useful and potentially non-invasive clinical tool for monitoring patients at risk of postoperative hypoxaemia.

Characterization and identification of the Detroit River mystery oil spill (2002)

In this paper, a case study of the Detroit River mystery oil spill (2002) is presented that demonstrates the utility of detailed and integrated oil fingerprinting in investigating unknown or suspected oil spills. The detailed diagnostic oil fingerprinting techniques include determination of hydrocarbon groups and semi-quantitative product screening, analysis of oil-characteristic biomarkers and the extended suite of parent and alkylated polycyclic aromatic hydrocarbons (PAHs), and quantitative determination of a variety of diagnostic ratios of "source-specific marker" compounds. The detailed chemical fingerprinting data and results highlight the followings: (1) The spill samples were largely composed of used lube oil mixed with smaller portion of diesel fuel. (2) The diesel in the samples had been weathered and degraded. (3) Sample 3 collected from N. Boblo Island on 14 April was more weathered (most probably caused by more evaporation and water-washing) than samples 1 and 2. (4) All fingerprinting results clearly demonstrated oils in three samples were the same, and they came from the same source. (5) Most PAH compounds were from the diesel portion in the spill samples, while the biomarker compounds were largely from the lube oil. (6) Input of pyrogenic PAHs to the spill samples was clearly demonstrated. The pyrogenic PAHs were most probably produced from combustion and motor lubrication processes, and the lube oil in these spill samples was waste lube oil.