Objective: To examine whether change in slow vital capacity (SVC) correlates to dyspnea improvement during emergency department (ED) treatment of chronic obstructive pulmonary disease (COPD) exacerbation.
Methods: We performed a prospective cohort study and enrolled consecutive patients during a 3-week period. ED patients > or = 55 years old with COPD exacerbation were asked to perform bedside spirometry shortly after ED arrival and again at discharge. SVC was measured first, then forced expiratory volume in the first second (FEV1), peak expiratory flow (PEF), and forced vital capacity (FVC). Concurrent with spirometry, patients rated their dyspnea on a 10-cm visual analogue scale.
Results: Thirty-six patients were enrolled. The median ED stay was 271 min (interquartile range 219-370 min). Seventy-one percent of the patients reported dyspnea improvement during their ED stay. Change in SVC was significantly higher among the patients whose dyspnea improved than among those whose did not (median increase of 0.15 L vs median decrease of 0.25 L, respectively, p < 0.01). By contrast, the change in spirometry values were similar for FEV1, PEF, and FVC (all p > 0.30). Spearman correlation supported these findings: SVC r = 0.45 (p = 0.02) versus nonsignificant correlation with FEV(1) (r = 0.33), PEF (r = -0.22), and FVC (r = 0.35).
Conclusions: Increase in SVC significantly correlated with dyspnea improvement among ED patients with moderate-to-severe COPD exacerbation. Change in SVC merits consideration when evaluating therapeutic response during COPD exacerbation.