PT  - JOURNAL ARTICLE
AU  - Katharine Hurt
AU  - Paolo Paredi
AU  - Harpal Kalsi
AU  - Margaret Hodson
AU  - Diana Bilton
AU  - Omar Usmani
TI  - Inspiratory and expiratory reactance at 5Hz in adult cystic fibrosis
DP  - 2011 Sep 01
TA  - European Respiratory Journal
PG  - p4557
VI  - 38
IP  - Suppl 55
4099  - http://erj.ersjournals.com/content/38/Suppl_55/p4557.short
4100  - http://erj.ersjournals.com/content/38/Suppl_55/p4557.full
SO  - Eur Respir J2011 Sep 01; 38
AB  - Introduction: Progressive airways obstruction is a key feature of cystic fibrosis (CF) which has it origins in the small airways. Reactance at 5Hz (X5), measured by impulse oscillometry (IOS), determines the capacitive properties of the peripheral lung. In COPD patients the respiratory phase difference in X5 (inspiratory-minus-expiratory, ΔX5) identifies individuals with expiratory flow limitation. Studies in CF, so far, have analysed whole breath impulse oscillometry.Aim: To determine the relationship between inspiratory and expiratory phase X5 with spirometry and body plethysmography.Methods: Within-breath analysis of IOS (Jaeger) was performed on 25 patients with CF (FEV1 range 26-119% of predicted). Results were correlated with spirometric and plethysmographic indices (Jaeger MasterLab).Results: Both inspiratory and expiratory X5 correlated with FEV1 (r= 0.842, p<0.0001; r=0.892, p<0.0001), respectively. The parameters showed greater sensitivity at lower FEV1 values. They also demonstrated an inverse linear relationship with RV/TLC% ratio (r=-0.747, p<0.0001: r=-0.817, p<0.0001). Respiratory phase difference (ΔX5) correlated with FEV1 and RV/TLC% (r=0.662, p<0.0001: r=0.659, p< 0.004). There was a greater unit change in ΔX5 in CF patients with lower FEV1 values (greater disease severity).Conclusion: Measurement of inspiratory and expiratory X5 are useful indices of airway obstruction and gas trapping in CF. IOS is quick, easy and portable to use at the patient bedside or outpatient clinic in contrast to body plethysmography. Calculating respiratory phase difference in X5 (ΔX5) may be a useful marker for identifying CF patients who have expiratory flow limitation.