Others have suggested that X at 5 Hz is most sensitive to changes in airway calibre. Buhr et al found that X determined by oscillometry significantly correlated with airway resistance determined using body plethysmography (r=0.86), and Ortiz and Menendez suggested that a 30% change in X following a bronchodilator challenge is approximately equal to a 12% increase in FEV1. Goldman et al proposed that the integrated X over a range of low frequencies (5 Hz to Fres) provides meaningful evidence of airflow obstruction beyond the sensitivity of spirometry. Still others have shown that Fres correlates best with baseline FEV1 (r=-0.55). Schmekel and Smith found that the change in Fres following EVH correctly diagnosed asthma with 89% sensitivity and 100% specificity. Our study showed that the changes from baseline in R5, Fres, X and AX following EVH were significantly greater for AHR+ subjects than for AHR- subjects. Moreover, all were significantly correlated with post-EVH change in FEV^ with highest sensitivities (90% at predetermined specificities of 80%) for per cent change in R5 and absolute postchallenge AX (cm H2O/L). Buy Asthma Inhalers Online
AHR in asthmatics is often associated with abnormalities in baseline lung function. In the present group of athletic subjects, baseline FEV1 was within a normal range; only two subjects demonstrated values that were 80% or less than that predicted, and FEF25-75 values were at or below 70% of the predicted values for five AHR+ subjects and two AHR- subjects. Baseline values in FEF25-75 were strongly correlated to baseline values in FEV1 and, similar to the results of others, we observed significant correlations between baseline spirometric parameters and baseline IOS measurements. No baseline lung functions determined using spirometry correlated with postexercise falls in FEV^ however, significant correlations with peak post-EVH falls in FEV1 were observed for baseline R5 and AX values.
Category: Lung function
Tags: Airway hyperresponsiveness, Dry air, Eucapnic voluntary hyperpnea, Exercise-induced bronchoconstriction, Forced oscillation