The Science Journal of the American Association for Respiratory Care

2011 OPEN FORUM Abstracts

RELATIONSHIP OF FEV1 AND COMPUTERIZED TOMOGRAPHIC EMPHYSEMA SCORES TO FUNCTION IN COPD.

Josh Boyd, Yuhchin Huang, Neil MacIntyre; Duke University, Durham, NC

BACKGROUND: COPD is a disease that can involve both the airways as well as alveolar structures. Conceptually, the spirometric forced expiratory volume in one second (FEV1) represents the airway or bronchitic component of COPD, while an emphysema score from a computerized tomographic (CT) scan represents the alveolar destructive component of COPD. HYPOTHESIS: We hypothesized that these two indices of COPD would correlate differently with various markers of function in COPD. METHODS: We analyzed 124 subjects in our database of COPD patients who were studied as part of the multicenter COPDGene project. We performed simple and stepwise multiple linear regression correlations of FEV1 (percent predicted) and emphysema score (visual scoring system ranging from 1-4 in 6 lung regions) with the following indices of function: Six minute walk distance (6MWD), change in SpO2 during the walk (dSpO2), diffusing capacity for carbon monoxide (DLCO), and a resting arterial CO2 calculation (CO2). RESULTS: Mean (range) for the measured values were: FEV1 48% (11 to 122%), Emphysema score 8.9 (0 to 22), 6MWD 1107 ft (56 to 1786 ft), dSpO2 -2% (-16 to +5%), DLCO 13.3 (4.8 to 25), CO2 46 torr (34 to 68 torr). FEV1 strongly correlated with all four functional measurements (P values ranged from .006 to .0001). Emphysema score correlated slightly better than FEV1 with dSpO2 and DLCO. However, this score did not correlate with 6MWD or CO2. CONCLUSIONS: These analyses suggest that the bronchitic component of COPD is highly correlated with all four measurements of function. In contrast, the emphysema score is largely correlated with only gas exchange parameters and appears to have less impact on exercise ability or control of breathing.
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