Emphysema associated with activity limitations in COPD
MedWire News: Results from a US study indicate that the extent of emphysema, but not airways disease, is associated with activity limitations in patients with chronic obstructive pulmonary disease (COPD).
"Reduction in exercise capacity is frequent in subjects with COPD and is traditionally associated with impaired lung function," explain Alejandro Diaz (Harvard Medical School, Boston Massachusetts) and team. "There is, however, increasing recognition that spirometric measures of lung function alone do not explain all the variance found in clinical measures of disease."
The team studied 93 patients with COPD, aged an average of 67 years, who had a mean FEV1 of 57.1% of the predicted value.
Computed tomography (CT) scans were used to assess emphysema extent, defined as the percentage of low attenuation areas less than a threshold of -950 Hounsfield units (%LAA-950), as well as the extent of airways disease, as indicated by the wall area percentage (WA%) of the 3rd to 6th generations of the apical bronchus of right upper lobe (RB1).
Exercise capacity was assessed using the 6-minute walk distance (6MWD) test.
Initial analysis indicated that 6MWD was inversely associated with %LAA-950 and with the WA% of the 6th generation of the RB1.
However, after adjustment for factors such as age, gender, and body mass index, as well as brand of CT scanner, only the association between 6MWD and %LAA-950 remained significant.
Indeed, a 10% increase in emphysema was associated with a 28.6-m reduction in 6MWD, after adjustment for confounding factors.
The researchers conclude in the journal Respiratory Medicine that "in this cohort emphysema but not airways disease contributed independently to exercise capacity as assessed by 6MWD."
However, they add that "further prospective studies involving larger study cohorts are needed to assess the observed relationship between CT indexes and exercise capacity."
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By Mark Cowen