Tidal Volume Single Breath Washout of Two Tracer Gases - A Practical and Promising Lung Function Test

Small airway disease frequently occurs in chronic lung diseases and may cause ventilation inhomogeneity (VI), which can be assessed by washout tests of inert tracer gas. Using two tracer gases with unequal molar mass (MM) and diffusivity increases specificity for VI in different lung zones. Currently washout tests are underutilised due to the time and effort required for measurements. The aim of this study was to develop and validate a simple technique for a new tidal single breath washout test (SBW) of sulfur hexafluoride (SF(6)) and helium (He) using an ultrasonic flowmeter (USFM)

Isotope separation by 'Taylor diffusion'

THE axial dispersion of injected diffusible matter in a fluid flowing in steady laminar regime through a tube has been described by Taylor. On this principle, a simple technical device enabling isotopic separation can be constructed. The separation factor for light stable isotopes is higher than that reached by standard methods; solar energy can be used as an energy source for its functioning. © 1978 Nature Publishing Group.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

A Meta-analysis of Asbestos and Lung Cancer: Is Better Quality Exposure Assessment Associated with Steeper Slopes of the Exposure-Response Relationships?

Background: Asbestos is a well-recognized cause of lung cancer, but there is considerable between-study heterogeneity in the slope of the exposure-response relationship.Objective: We considered the role of quality of the exposure assessment to potentially explain heterogeneity in exposure-response slope estimates.Data sources: We searched PubMed MEDLINE (1950-2009) for studies with quantitative estimates of cumulative asbestos exposure and lung cancer mortality and identified 19 original epidemiological studies. One was a population-based case-control study, and the others were industry-based cohort studies.Data extraction: Cumulative exposure categories and corresponding risks were abstracted. Exposure-response slopes [KL (lung cancer potency factor of asbestos)] were calculated using linear relative risk regression models.Data synthesis: We assessed the quality of five exposure assessment aspects of each study and conducted random effects univariate and multivariate meta-regressions. Heterogeneity in exposure-response relationships was greater than expected by chance (I2 = 64%). Stratification by exposure assessment characteristics revealed that studies with well-documented exposure assessment, larger contrast in exposure, greater coverage of the exposure history by exposure measurement data, and more complete job histories had higher meta-KL values than did studies without these characteristics. The latter two covariates were most strongly associated with the KL value. Meta-KL values increased when we incrementally restricted analyses to higher-quality studies.Conclusions: This meta-analysis indicates that studies with higher-quality asbestos exposure assessment yield higher meta-estimates of the lung cancer risk per unit of exposure. Potency differences for predominantly chrysotile versus amphibole asbestos-exposed cohorts become difficult to ascertain when meta-analyses are restricted to studies with fewer exposure assessment limitations