8 research outputs found
Recommended from our members
Recovery of semi-volatile organic compounds during sample preparation: Compilation for characterization of airborne particulate matter
Semi-volatile compounds present special analytical challenges not met by conventional methods for analysis of ambient particulate matter (PM). Accurate quantification of PM-associated organic compounds requires validation of the laboratory procedures for recovery over a wide volatility and polarity range. To meet these challenges, solutions of n-alkanes (nC{sub 12} to nC{sub 40}) and polycyclic aromatic hydrocarbons PAHs (naphthalene to benzo[ghi]perylene) were reduced in volume from a solvent mixture (equal volumes of hexane, dichloromethane and methanol), to examine recovery after reduction in volume. When the extract solution volume reached 0.5 mL the solvent was entirely methanol, and the recovery averaged 60% for n-alkanes nC{sub 12} to nC{sub 25} and PAHs from naphthalene to chrysene. Recovery of higher MW compounds decreased with MW, because of their insolubility in methanol. When the walls of the flasks were washed with 1 mL of equal parts hexane and dichloromethane (to reconstruct the original solvent composition), the recovery of nC{sub 18} and higher MW compounds increased dramatically, up to 100% for nC{sub 22}-nC{sub 32} and then slowly decreasing with MW due to insolubility. To examine recovery during extraction of the components of the High Capacity Integrated Gas and Particle Sampler, the same standards were used to spike its denuders and filters. For XAD-4 coated denuders and filters, normalized recovery was > 95% after two extractions. Recovery from spiked quartz filters matched the recovery from the coated surfaces for alkanes nC{sub 18} and larger, and for fluoranthene and larger PAHs. Lower MW compounds evaporated from the quartz filter with the spiking solvent. This careful approach allowed quantification of organics by correcting for volatility- and solubility-related sample preparation losses. This method is illustrated for an ambient sample collected with this sampler during the Texas Air Quality Study 2000
Predictors of mortality and ICD shock therapy in primary prophylactic ICD patients-A systematic review and meta-analysis.
BACKGROUND: There is evidence that the benefit of a primary prophylactic ICD therapy is not equal in all patients.
PURPOSE: To evaluate risk factors of appropriate shocks and all- cause mortality in patients with a primary prophylactic ICD regarding contemporary studies.
DATA SOURCE: PubMed, LIVIVO, Cochrane CENTRAL between 2010 and 2016.
STUDY SELECTION: Studies were eligible if at least one of the endpoints of interest were reported.
DATA EXTRACTION: All abstracts were independently reviewed by at least two authors. The full text of all selected studies was then analysed in detail.
DATA SYNTHESIS: Our search strategy retrieved 608 abstracts. After exclusion of unsuitable studies, 36 papers with a total patient number of 47282 were included in our analysis. All-cause mortality was significantly associated with increasing age (HR 1.41, CI 1.29-1.53), left ventricular function (LVEF; HR 1.21, CI 1.14-1.29), ischemic cardiomyopathy (ICM; HR 1.37, CI 1.14-1.66) and co-morbidities such as impaired renal function (HR 2.30, CI 1.97-2.69). Although, younger age (HR 0.96, CI 0.85-1.09), impaired LVEF (HR 1.26, CI 0.89-1.78) and ischemic cardiomyopathy (HR 2.22, CI 0.83-5.93) were associated with a higher risk of appropriate shocks, none of these factors reached statistical significance.
LIMITATIONS: Individual patient data were not available for most studies.
CONCLUSION: In this meta-analysis of contemporary clinical studies, all-cause mortality is predicted by a variety of clinical characteristics including LVEF. On the other hand, the risk of appropriate shocks might be associated with impaired LVEF and ischemic cardiomyopathy. Further prospective studies are required to verify risk factors for appropriate shocks other than LVEF to help select appropriate patients for primary prophylactic ICD-therapy.peerReviewe