Grading the Severity of Obstruction in Mixed Obstructive-Restrictive Lung Disease.
Chest. 2011 Mar 17;
Authors: Gardner ZS, Ruppel GL, Kaminsky DA
ABSTRACT BACKGROUND: The severity of obstructive pulmonary disease is determined by the percent predicted FEV(1) based on ATS/ERS guidelines. In patients with coexisting restrictive lung disease, the decrease in FEV(1) can overestimate the degree of obstruction. We hypothesize that adjusting the FEV(1) for the decrease in TLC results in a more appropriate grading of the severity of obstruction. METHODS: We examined a large PFT database and identified patients with both restrictive (TLC < 80% predicted) and obstructive (FEV(1)/FVC < the lower limit of normal) lung disease. FEV(1) percent predicted was adjusted for the degree of restriction by dividing it by percent predicted TLC. We compared the distribution of severity grading between adjusted and unadjusted values according to ATS/ERS criteria, and determined how the distribution of severity would change based on asthma and COPD guidelines. RESULTS: We identified 199 patients with coexisting restrictive and obstructive lung disease. By ATS/ERS grading, the unadjusted data categorized 76% of patients as having severe or very severe obstruction, and 11% as having mild or moderate obstruction. The adjusted data classified 33% with severe or very severe obstruction, and 44% with mild or moderate obstruction. Of the corrected values, 83% resulted in a change to less severe obstruction by ATS/ERS guidelines, and 44% and 70% of patients, respectively, would be reclassified as having less severe obstruction by current asthma and COPD guidelines. CONCLUSIONS: This method results in a more appropriate distribution of severity of obstruction, which should lead to more accurate treatment of obstruction in these patients.
PMID: 21415132 [PubMed – as supplied by publisher]
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