Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States. Although the forced expiratory volume (FEV1) is an accurate marker of mortality in population studies it has only shown a weak correlation with dyspnea and quality of life. It has been shown that changes in inspiratory capacity (IC), a measure of hyperinflation, correlate well with improvements in these outcomes. The aim of this study is to determine whether a single, baseline measurement of IC is a better predictor of measures of dyspnea and quality of life than FEV1.
We enrolled veterans with COPD from two pulmonary clinics. Demographic data was obtained and enrollees completed three questionnaires, the Medical Research Council Dyspnea Scale (MRC), the University of California San Diego (UCSD) Shortness of Breath Questionnaire and the St. George’s Hospital Respiratory Questionnaire (SGRQ). Spirometry was performed according to ATS standards and FEV1 and IC measurements were recorded. Correlation coefficients between FEV1, IC, and questionnaire scores were then determined and compared.
36 patients were enrolled. The mean age of our participants was 66 with the majority being Caucasian males (95%). The mean number of pack-years smoked was 71. The mean IC among enrollees was 68% predicted. The mean FEV1 was 40% predicted indicating severe airflow obstruction. The mean scores for the MRC, UCSD and SGRQ were 3.3, 67.5, and 46.5 respectively. Both FEV1 (r=-0.58, p<0.001) and IC (r=-0.47, p=0.004) correlated with the UCSD score though neither measure was superior (p=0.53). Neither FEV1 (r=-0.24, p=0.15) nor IC (r=-0.28, p=0.10) correlated with the MRC. FEV1 correlated with the SGRQ (r=-0.37, p=0.02) while IC (r=-0.24, p=0.15) did not.
In patients with severe COPD, a single baseline measurement of IC does not appear to be better predictor of dyspnea or quality of life scores than FEV1.
Clinicians should be mindful that no spirometric measure is reliably predictive of symptoms and quality of life in COPD.
Shirley Jones, None.