The concept of using pulmonary function tests to place subjects into physiologic “buckets” using the interpretation algorithm of the American Thoracic Society/European Respiratory Society task force. The concept of using pulmonary function tests to place subjects into physiologic “buckets” using the interpretation algorithm of the American Thoracic Society/European Respiratory Society task force. VC = vital capacity. LLN = lower limit of normal. PV = pulmonary vascular. CW = chest wall. NM = neuromuscular. CB = chronic bronchitis. (From Reference 1, with permission.) Neil R MacIntyre Respir Care 2012;57:154-164 (c) 2012 by Daedalus Enterprises, Inc.