Lung function measured by impulse oscillometry and spirometry following eucapnic voluntary hyperventilation: RESULTS (2)

Airway response to EVH
Peak post-EVH measurements from IOS were significantly greater than baseline values for AHR+ and AHR- subjects (P<0.05). Baseline IOS measurements were not different between AHR+ and AHR- subjects; however, postchallenge peak IOS values were different between subject groups (Figure 1; P<0.05). Per cent changes for AHR+ and AHR- subjects in R5, Fres, X and AX were 70.3 versus 37.9, 82.6 versus 48.6, 175.9 versus 70.8, and 567.8 versus 267.0, respectively. When computed as a per cent change from baseline, only the per cent change in peak R5 was significantly greater for AHR+ subjects (P<0.05); Fres, X and AX per cent changes were not significantly different between AHR groups. The pattern of change in R5 values at 10 min after EVH was similar to that observed for FEV1 (Figure 2); however, resistance at 15 min after EVH was not different between groups. ventolin inhalers

Relationship between spirometry and IOS
Peak increase in R5 was significantly correlated with peak increases in Fres, X and AX (r=0.79, -0.94 and 0.98, respectively; P<0.05). Peak increase in Fres was significantly correlated with peak increases in X and AX (r=-0.83 and 0.84, respectively; P<0.05). Peak increase in X was significantly correlated to peak AX (r=-0.96; P<0.05). Per cent peak fall in FEV1 was significantly correlated with peak increases in ^ Fe, X and AX expressed as raw values (r=-0.74, -0.70, 0.659 arneds -0.73, respectively; P<0.05) (Figure 3) and to per cent change (from baseline) in R5, Fres, X and AX (r=-0.66, -0.47, -0.57 and -0.46, respectively; P<0.05) (Figure 4). Per cent peak fall in FEF25 75 was significantly correlated with peak increases in R5, Fres, X and AX as raw values (r=-0.57, -0.63, 0.58 and -0.57, respectively; P<0.05) and to per cent increases in ^ Fres, X and AX (r=-0.58, -0.49, -0.56 and -0.4, respectively; P<0.05).

Figure_1

Figure 1) Posteucapnic voluntary hyperventilation (EVH) values for airway resistance at 5 Hz (R5), resonant frequency (F ), reactance (X) and area of reactance integrated from 5 Hz to Fres (AX) were significantly greater for baseline values for both airway hyper-responsive (AHR+) and normal (AHR-) subjects (*P<0.05), and were greater for AHR+ subjects than for AHR- subjects (fP<0.05)

Figure_2

Figure 2) The persistence of airway obstruction in airway hyperre-sponsive (AHR+) versus normal (AHR-) subjects over 15 min after the completion of eucapnic voluntary hyperventilation measured by per cent change in forced expiratory volume in 1 s (FEV1; panel A), airway resistance at 5 Hz (R5; panel B), and per cent change in R5 (panel C)

Figure_3

Figure 3) Peak changes in airway resistance at 5 Hz (R5) (A), resonant frequency (Fres) (B), reactance (X) at 5 Hz (C), and area of reactance integrated from 5 Hz to Fres (AX) (D) after eucapnic voluntary hyperventilation were significantly correlated to peak per cent change in forced expiratory volume in 1 s (FEV1) (P<0.05). Cutoff reference lines indicate a 10% fall in FEV1 and 80% specificity for impulse oscillometry indices. Sensitivities were 80%o for R5, Fres and X, and 90% for AX

Figure_4

Figure 4) Peak per cent change in airway resistance at 5 Hz (R5) was significantly correlated to peak per cent change in forced expiratory volume in 1 s (FEV1). At 80% specificity, a 50%o change in R5 demonstrated high sensitivity, only missing one subject positive for FEVt, indicating reasonable agreement with per cent fall in FEVj


Category: Lung function

Tags: Airway hyperresponsiveness, Dry air, Eucapnic voluntary hyperpnea, Exercise-induced bronchoconstriction, Forced oscillation