The two components of impedance are resistance and reactance. Bisgaard and Klug have shown that reactance (X) at 5 Hz has the lowest intra- and between-individual variability, and has a sensitivity equal to that of airway conductance. Others have suggested that airway resistance at 5 Hz (R5) is sensitive to obstruction. Goldman et al demonstrated that the area of X integrated from 5 Hz to resonant frequency (Fres), otherwise known as AX, is sensitive for detecting changes in bronchomo-tor tone in adolescent asthmatics. Schmekel and Smith found that the response in Fres has the most discriminative capacity to correctly diagnose asthma — asthma inhalers. Although the clinical efficacy of measuring respiratory impedance using IOS has been demonstrated, its use has not been widespread in assessing airflow obstruction.
In the present study, we compared airway responses with a 6 min EVH challenge using IOS and forced expiratory flow (FEF) manoeuvre values in airway hyperresponsive (AHR+) athletes and normal (AHR-) athletes and assessed the sensitivity and specificity of IOS to spirometry measures for identifying airway hyperresponsiveness. We correlated R5, Fres, X and AX to FEV1, and suggested cutoff criteria for these IOS measurements for determining airway hyperresponsiveness.
Category: Lung function
Tags: Airway hyperresponsiveness, Dry air, Eucapnic voluntary hyperpnea, Exercise-induced bronchoconstriction, Forced oscillation