Airways Obstruction From Asbestos Exposure: Analysis of Residuals
To provide a second check on the differences between groups, we calculated the residuals. In effect, this comparison age matches each individual and minimizes the effects of differences in age distributions within groups being compared. Thus, we subtracted each man’s measurements from his predicted value to obtain the residuals for FVCi, FEVi, flows, and TLC. The means of the residuals, the average differences from predicted for each group, were compared by t test in the three smoking categories and are shown in Table 2 for asbestos-exposed and unexposed men, in Table 3 for men with asbestosis and unexposed men, and in Table 4 for men with asbestosis compared with asbestos-exposed men. flovent inhalers
Regression models were developed for each measurement of flow and volume as dependent variables and ILO profusion and duration of asbestos exposure as independent variables. Significance of coefficients was calculated and proportion of variance explained by each, adjusted for degrees of freedom expressed as adjusted r2. Box plots (Fig 1 and 2) show the regression relationships between mid-flow (FEF25-75) and of air trapping (RV/ TLC) vs ILO profusion category. In the plots the middle line shows median (50th percentile) value, the 75 percent and 25 percent limits are the top and bottom of the box, and whiskers, extending three halves of the interquartile range, are rolled back to where there are data, and outliers are plotted as circles.
There were 1Д46 white men in both asbestos-exposed and asbestosis groups. Each group included 119 who had never smoked cigarettes, 722 current cigarette smokers, and 305 ex-smokers. Groups were compared as means and their pulmonary functions as mean percent predicted horizontally for the effect of asbestos and vertically for effect of smoking (Table 2).
When 119 asbestos-exposed men without asbestosis who had never smoked (column B, Table 2) were compared by t test to controls without exposure (column A), they showed significant lower FEF75-85 and FEVi/FVC and higher TLC and RV/TLC (A to A, Table 2, top section).