Lung function in adults with stable but severe asthma: air trapping and incomplete reversal of obstruction with bronchodilation

• Published in: Journal of applied physiology (1985) Vol. 104; no. 2; pp. 394 - 403
• Main Authors: Sorkness, Ronald L, Bleecker, Eugene R, Busse, William W, Calhoun, William J, Castro, Mario, Chung, Kian Fan, Curran-Everett, Douglas, Erzurum, Serpil C, Gaston, Benjamin M, Israel, Elliot, Jarjour, Nizar N, Moore, Wendy C, Peters, Stephen P, Teague, W. Gerald, Wenzel,, Sally E, National Heart, Lung, and Blood Institute Severe Asthma Research Program
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.02.2008; American Physiological Society
• Subjects: Adrenal Cortex Hormones - therapeutic use; Adult; Adults; Airway management; Airway Resistance - drug effects; Albuterol - pharmacology; Albuterol - therapeutic use; Asthma; Asthma - diagnosis; Asthma - drug therapy; Asthma - physiopathology; Biological and medical sciences; Bronchial Provocation Tests; Bronchoconstriction - drug effects; Bronchoconstrictor Agents; Bronchodilator Agents - pharmacology; Bronchodilator Agents - therapeutic use; Female; Forced Expiratory Volume; Fundamental and applied biological sciences. Psychology; Humans; London; Lung - drug effects; Lung - physiopathology; Lung Volume Measurements; Lungs; Male; Methacholine Chloride; Middle Aged; Phenotype; Respiratory function; Severity of Illness Index; Spirometry; Trapping; United States; Vital Capacity; London; United States; Human; Bronchodilation; Lung disease; Closure; Respiratory disease; airway closure; Respiratory system; Obstruction; Asthma; Respiratory tract; Vertebrata; Lung function; Mammalia; difficult asthma; fixed obstruction; Bronchus disease; Adult; Obstructive pulmonary disease
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00329.2007

1 University of Wisconsin, Madison, Wisconsin; 2 Wake Forest University, Winston-Salem, North Carolina; 3 University of Pittsburgh, Pittsburgh, Pennsylvania; 4 University of Texas Medical Branch, Galveston, Texas; 5 Washington University, St. Louis, Missouri; 6 Imperial College, London, United Kingdom; 7 National Jewish Medical and Research Center, Denver, Colorado; 8 Cleveland Clinic, Cleveland, Ohio; 9 University of Virginia, Charlottesville, Virginia; 10 Brigham & Women's Hospital, Boston, Massachusetts; and 11 Emory University, Atlanta, Georgia Submitted 23 March 2007 ; accepted in final form 7 November 2007 Five to ten percent of asthma cases are poorly controlled chronically and refractory to treatment, and these severe cases account for disproportionate asthma-associated morbidity, mortality, and health care utilization. While persons with severe asthma tend to have more airway obstruction, it is not known whether they represent the severe tail of a unimodal asthma population, or a severe asthma phenotype. We hypothesized that severe asthma has a characteristic physiology of airway obstruction, and we evaluated spirometry, lung volumes, and reversibility during a stable interval in 287 severe and 382 nonsevere asthma subjects from the National Heart, Lung, and Blood Institute Severe Asthma Research Program. We partitioned airway obstruction into components of air trapping [indicated by forced vital capacity (FVC)] and airflow limitation [indicated by forced expiratory volume in 1 s (FEV 1 )/FVC]. Severe asthma had prominent air trapping, evident as reduced FVC over the entire range of FEV 1 /FVC. This pattern was confirmed with measures of residual lung volume/total lung capacity (TLC) in a subgroup. In contrast, nonsevere asthma did not exhibit prominent air trapping, even at FEV 1 /FVC <75% predicted. Air trapping also was associated with increases in TLC and functional reserve capacity. After maximal bronchodilation, FEV 1 reversed similarly from baseline in severe and nonsevere asthma, but the severe asthma classification was an independent predictor of residual reduction in FEV 1 after maximal bronchodilation. An increase in FVC accounted for most of the reversal of FEV 1 when baseline FEV 1 was <60% predicted. We conclude that air trapping is a characteristic feature of the severe asthma population, suggesting that there is a pathological process associated with severe asthma that makes airways more vulnerable to this component. airway closure; difficult asthma; fixed obstruction Address for reprint requests and other correspondence: R. L. Sorkness, Univ. of Wisconsin, 777 Highland Ave., Madison, WI 53705 (e-mail: rlsorkne{at}wisc.edu )