Determinants of Percent Predicted FEVi in Current Asthmatic Subjects: Conclusion

A concurrent diagnosis of chronic bronchitis was also related to %FEVi, a finding that correlates with results which we reported in our comparison among subjects with different types of airway obstructive disease. In that article, we found that subjects with only asthma had much higher %FEVi results than subjects with combined diagnoses, such as asthma plus chronic bronchitis. In our current analyses, which were cross-sectional in design, the diagnosis of chronic bronchitis could have either preceded or followed the diagnosis of asthma. Because cough or phlegm (the symptoms usually associated with chronic bronchitis), or both, did not significantly predict %FEVi in our subjects, we suspect that physicians labelled subjects with the most frequent exacerbations, perhaps secondary to acute respiratory infections, as having both chronic bronchitis and asthma. Thus, as with subjects with severe wheeze, the correlation of a diagnosis of chronic bronchitis with %FEVi is probably another correlation with disease severity. flovent inhaler

In other analyses, we did not find pack-years of cigarette use related to %FEVi. As calculated from the characteristics of enrollment, the average number of pack-years in our population of asthmatic subjects was approximately 9.0. As we have reported in a previous study on the effect of pack-years on pulmonary function, after 9.0 pack-years of smoking, subjects of the Tucson study still have a mean %FEVi above 95 percent, so it is not surprising that we did not detect an influence of cigarette smoking on lung function. The relatively low number of pack-years recorded in our asthmatic subjects makes us suspect that our asthmatic subjects, because of their respiratory symptoms, usually give up cigarette smoking or at least cut back substantially before it does produce permanent respiratory impairment.
While we have shown in previous studies that Tucson asthmatic subjects do have a greater rate of allergy skin test reactivity, higher eosinophil counts, and higher levels of serum IgE (adjusted for age and sex) than nonasthmatic subjects, we did not find in the present study that these markers of an allergic disposition correlated with pulmonary function among the asthmatic subjects. Also, in analyses we have not shown here, these markers did not relate to severity of wheeze. Other investigators also have reported that allergy skin test reactivity and serum IgE do not relate to FEVi, even in longitudinal analyses.

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