Introduction: The aim of this study was to gain insight into the physiological changes occurring in subjects with cystic fibrosis (CF) after autogenic drainage (AD). Changes in respiratory system resistance (Rrs), reactance (Xrs), and spirometry were analyzed in adult CF subjects after a single AD physiotherapy session.
Methods: This prospective observational study was conducted during the annual check-up of adult CF subjects in stable condition. Spirometry and Rrs and Xrs measurements using the forced oscillations technique at 5, 11, and 19 hertz (Hz) were performed before and 30 min after a 20-min AD session. Control CF subjects were tested at baseline and 50 min without AD. Results are expressed as mean ± standard deviation or median [interquartile range].
Results: Thirty subjects were included in the physiotherapy group (age 29 [25-34] years, forced expiratory volume in 1 s (FEV1) 40.3 [30.1-57.9]% predicted) and 11 in the control group (age 31 [28.5-36.5] years, FEV1 43.6 [31.1-51.9] % predicted). No significant changes in any parameter were observed in the control group. AD modestly but significantly increased the forced vital capacity (FVC) and FEV1 (p<0.001). Inspiratory resistance was also significantly improved by AD: Rrs5 from 5.74±2.39 to 5.24±2.17 cmH2O/L/s, p<0.05; Rrs11 from 4.83±1.98 to 4.32±1.7 cmH2O/L/s, p = 0.003; and Rrs19 from 4.18 [3.46-5.07] to 3.86 [2.76-4.98] cmH2O/L/s, p<0.001. In contrast, AD had no significant effects on frequency dependence of resistance (Rrs5-Rrs19) or expiratory resistance. Inspiratory Xrs5, but not ΔXrs5 (expiratory-inspiratory Xrs), was improved by AD (p<0.05). Moderate correlations were detected between the improvement in FEV1 and FVC and inspiratory resistance (r = 0.53, p = 0.005 and r = 0.44, p = 0.02, respectively).
Conclusion: A single session of AD improved inspiratory airway resistance, except in the distal airways. The forced oscillations technique provides a new tool for understanding the pathophysiological effects of airway clearance physiotherapy in CF.