Schema depicting chronic obstructive pulmonary disease (COPD) Schema depicting chronic obstructive pulmonary disease (COPD). A nonproportional Venn diagram shows subsets of patients with chronic bronchitis, emphysema, and asthma in three overlapping circles. Subsets of patients lying within the rectangle have airway obstruction. Patients with asthma (subset 9) are defined as having completely reversible airway obstruction and lie entirely within the rectangle; their diagnosis is unequivocal. Patients in subsets 6 and 7 have partially reversible airway obstruction with chronic productive cough or emphysema, respectively. Patients in subset 8 have features of all three disorders. It may be difficult to ascertain whether patients in subsets 6 and 8 indeed have asthma or whether they have developed bronchial hyperreactivity as a complication of chronic bronchitis or emphysema; the history helps. Patients in subset 3 have chronic productive cough with airway obstruction but no emphysema; it is not known how large this subset is, because epidemiologic studies with the CT scan, the most sensitive in vivo imaging technique for the diagnosis or exclusion of emphysema, are not available. It is much easier to identify patients with emphysema determined by chest radiograph who do not have bronchitis (subset 4). Most patients who require medical care for their disease fall into subsets 5 and 8. Patients in subsets 1 and 2 do not have airway obstruction as determined by the FEV1 but have clinical or radiographic features of chronic bronchitis or emphysema, respectively. Because COPD, when defined as a process, does not have airway obstruction as a defining characteristic, and because pure asthma is not included in the term COPD, patient subsets 1 to 8 are included within the areas outlined by the shaded band, which denotes COPD. (Reproduced with permission from Snider GL, Faling LJ, Rennard SI. Chronic bronchitis and emphysema. In: Murray JF (ed). Respiratory Medicine, 2nd ed. Philadelphia: WB Saunders, 1994:1334. Copyright Elsevier.) Source: Surgical Management of Emphysema, Johns Hopkins Textbook of Cardiothoracic Surgery Citation: Yuh DD, Vricella LA, Yang SC, Doty JR. Johns Hopkins Textbook of Cardiothoracic Surgery; 2014 Available at: http://accesssurgery.mhmedical.com/ViewLarge.aspx?figid=55166346&gbosContainerID=0&gbosid=0 Accessed: December 28, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved