A significant response to EVH was obtained; mean postchallenge per cent peak falls for respective AHR+ and AHR- subjects were 30.6± 14.0% and 7.5±2.6% for FEV1, and 50.7±17.8% and 22.4±7.7% for FEF25-75. The falls for1 the AHR- group were substantially greater than expected. Rundell et al obtained a fall of 4.7±3.2% after EVH in 21 AHR- subjects, suggesting that underlying hyperreactivity could have been present in our control population; only two subjects in the AHR- group had peak falls in FEV1 of less than 7.5%. Interestingly, those two subjects were the only subjects that demonstrated post-EVH increases in R5 of less than 20% (9.5% and 13.0%; Figure 4). The cutoff value to define reversible airway obstruction is usually based on the mean plus two standard deviations of the response in healthy subjects. Although we used the widely accepted cutoff of a 10% fall in FEVp values of 7.5% and 6.5% have been suggested to define AHR in elite cold weather athletes and elite Finnish runners, respectively. buy asthma inhalers
Respiratory impedance was evaluated using IOS and compared with FEV1 and FEF25-75 values obtained from spirometry. The IOS manoeuvre involves tidal breathing for 20 s to 30 s while respiratory flow is overlaid with pulses emitted from a loudspeaker. Based on the airflow response, impedance estimated as the spectral ratio between pressure and flow through 5 Hz to 35 Hz is resolved into resistance and X. Debate exists concerning which is more discriminating when detecting airway obstruction; however, it is widely accepted that IOS measurements are frequency-dependent with the pronounced changes occurring at lower frequencies. Some studies have shown that resistance at 5 Hz significantly correlates with baseline FEV1, postmethacholine challenge FEVj or1 postbronchodilator FEV1 values 1.
Category: Lung function
Tags: Airway hyperresponsiveness, Dry air, Eucapnic voluntary hyperpnea, Exercise-induced bronchoconstriction, Forced oscillation