Gas transfer predicts survival in lung disease patients

By Mark Cowen, Senior medwireNews Reporter

Gas transfer is the best lung function predictor of survival in patients with chronic obstructive pulmonary disease (COPD), study results suggest.

Nicholas Hopkinson (Imperial College, London, UK) and colleagues found that the percent of predicted carbon monoxide diffusion capacity (DLCO), as well as arterial oxygen partial pressure (PaCO₂) and age, were significantly and independently associated with survival in patients with COPD.

"An argument can therefore be made for performing measures of gas transfer in routine practice for patients with COPD to provide them with the best prognostic information, and future classifications of COPD should include DLCO and not rely merely on the severity of airflow obstruction," comment Hopkinson and team.

They add: "The results may also inform trial design, suggesting that gas transfer should also be used for stratification where therapies that are intended to influence mortality are to be tested."

The team studied data on 604 COPD patients (mean age 61.9 years) who underwent lung function testing, including arterial blood gas analysis, between 1996 and 2010. The participants had a mean 37% of predicted forced expiratory volume in 1 second

Over a mean follow-up period of 80 months, 229 patients (37.9%) died. Median survival for the patients was 91.9 months.

In multivariate regression analysis, the team found that DLCO was an independent predictor of survival in the patients.

Indeed, compared with patients in the lowest quartile for percent of predicted DLCO (<27.9% predicted), those in the highest (>51% predicted) and second highest (51-37.3% predicted) quartiles were a respective 67% and 48% less likely to die over the study period.

Younger age and increased PaCO₂ were also significant predictors of survival in patients.

Staging according to Global Initiative for Chronic Obstructive Lung Disease criteria, other lung function parameters, anthropometric measures, and exacerbation history did not provide any additional prognostic information.

Hopkinson and team conclude in the European Respiratory Journal: "The main finding of the present study was that in stable outpatients with

COPD DLCO %predicted and PaO2 as well as younger age were the only

variables independently associated with survival."

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