Lung Mechanics and Dyspnea during Exacerbations of Chronic Obstructive Pulmonary Disease

Abstract

Exacerbation of chronic obstructive pulmonary disease commonly causes hospitalization. The change in lung mechanics during exacerbation and its relationship to symptoms in spontaneously breathing individuals has not been described. We hypothesized that changes in both airflow and lung volumes would occur during an exacerbation, but that only volume change would relate to symptomatic improvement. Lung mechanics and resting dyspnea were recorded in 22 hospitalized patients during recovery from exacerbation. Spirometry, inspiratory capacity, respiratory system resistance and reactance, tidal breathing patterns, and expiratory flow limitation were recorded after nebulized bronchodilator therapy on the first 3 d after admission, at discharge, and 6 wk postadmission (Day 42). Prebronchodilator measurements were taken on Day 2, at discharge, and on Day 42. Postbronchodilator inspiratory capacity increased 0.23 +/- 0.07 L by discharge and 0.42 +/- 0.1 L by Day 42, FEV1 rose 0.09 +/- 0.04 and 0.2 +/- 0.05 L at discharge and Day 42, respectively, and FVC increased 0.21 +/- 0.08 and 0.47 +/- 0.09 L at discharge and Day 42 (all p < 0.05). Consistent reduction in dyspnea was seen as the exacerbation resolved. Respiratory system resistance, FEV1/FVC, and expiratory flow limitation were unchanged throughout, indicating that changes in lung volume rather than airflow resistance predominated. Improvement in operating lung volumes is the principal change seen as a chronic obstructive pulmonary disease exacerbation resolves and increase in inspiratory capacity is a useful guide to a reduction in dyspnea.