Introduction: Within-breath reactance from forced oscillometry estimates resistance via its inspiratory component (Xrs,insp) and flow limitation via its expiratory component (Xrs,exp). This study assessed whether reactance could detect recovery from an exacerbation of chronic obstructive pulmonary disease (COPD).
Method: Thirty-nine COPD subjects with an exacerbation were assessed on three occasions over six weeks using post-bronchodilator forced oscillometry, arterial blood gases, spirometry including inspiratory capacity, symptoms and health related quality of life (HRQOL).
Results: Significant improvements were seen in all spirometric variables except the ratio of forced expiratory volume in 1 second (FEV1) and vital capacity (VC), ranging in mean (SEM) size from 11.0 (2.2) % predicted for peak expiratory flow to 12.1 (2.3) % predicted for VC at 6 weeks. There was an associated increase in arterial partial pressure of oxygen (PaO2). There were significant mean (SEM) increases in both Xrs,insp and Xrs,exp (27.4 (6.7) % and 37.1 (10.0) % respectively) but no change in oscillometry resistance (Rrs) values. Symptom scales and HRQOL scores improved. With most variables the largest improvement occurred within the first week with spirometry having the best signal to noise ratio. Changes in symptoms and HRQOL correlated best with changes in FEV1, PaO2 and Xrs,insp.
Conclusions: The physiological changes seen following an exacerbation of COPD comprised both an improvement in operating lung volumes and a reduction in airway resistance. Given the ease with which forced oscillometry can be performed in these subjects, measurements of Xrs,insp and Xrs,exp could be useful for tracking recovery.
- Acute Exacerbation
- Chronic Obstructive Pulmonary Disease
- Forced Oscillometry