Diagnostic Considerations

Common alternative diagnoses and suggestive diagnostic features are as follows:

Congestive heart failure: This condition may produce wheezing and is often difficult to differentiate from emphysema. However, a history of orthopnea and paroxysmal nocturnal dyspnea, the presence of fine basal crackles, and typical findings on chest radiographs can lead to the diagnosis of congestive heart failure.
Bronchiectasis: Patients with bronchiectasis have chronic production of copious purulent sputum, coarse crackles and clubbing upon physical examination, and abnormal findings on chest radiographs and CT scans.
Bronchiolitis obliterans: Obliterative bronchiolitis is observed in younger persons who do not smoke and in persons with collagen-vascular diseases. A CT scan characteristically shows areas of mosaic attenuation without evidence of generalized emphysema.
Chronic asthma: The delayed onset of severe asthma may be difficult to distinguish in older patients, but the important distinction is a significant bronchodilator response and normal diffusion (ie, diffusing capacity of lung for carbon monoxide [DLCO]) on pulmonary function tests.

Differential Diagnoses

Workup

Pahal P, Avula A, Sharma S. Emphysema. StatPearls [Internet]. 2019 Jan. [QxMD MEDLINE Link]. [Full Text].
[Guideline] Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. 2018. 142. [Full Text].
Shah PL, Herth FJ, van Geffen WH, Deslee G, Slebos DJ. Lung volume reduction for emphysema. Lancet Respir Med. 2017 Feb. 5 (2):147-56. [QxMD MEDLINE Link].
Cottin V, Nunes H, Brillet PY, Delaval P, Devouassoux G, Tillie-Leblond I, et al. Combined pulmonary fibrosis and emphysema: a distinct underrecognised entity. Eur Respir J. 2005 Oct. 26(4):586-93. [QxMD MEDLINE Link].
Goss AM, Morrisey EE. Wnt signaling and specification of the respiratory endoderm. Cell Cycle. 2010 Jan 1. 9(1):10-1. [QxMD MEDLINE Link].
[Guideline] Reddell, H, Vogelmeier C, Decker R et al. Asthma, COPD, and Asthma-COPD overlap: A joint project of GINA and GOLD. ginaasthma.org. Available at http://ginasthma.org/2017-gina-report-global-strategy-for-asthma-management-and-prevention/. April 2017; Accessed: December 27, 2017.
National Center for Chronic Disease Prevention and Health Promotion, Division of Population Health. Chronic Obstructive Pulmonary Disease (COPD). CDC.gov. Available at https://www.cdc.gov/copd/index.html. August 4, 2017; Accessed: December 27, 2017.
Rega PP. Phosgene Toxicity. Medscape Drugs &Diseases. Available at http://emedicine.medscape.com/article/832454-overview. January 30, 2015; Accessed: August 31, 2016.
Liu Y, Yan S, Poh K, Liu S, Iyioriobhe E, Sterling DA. Impact of air quality guidelines on COPD sufferers. Int J Chron Obstruct Pulmon Dis. 2016. 11:839-72. [QxMD MEDLINE Link].
Anthonisen NR, Connett JE, Murray RP. Smoking and lung function of Lung Health Study participants after 11 years. Am J Respir Crit Care Med. 2002 Sep 1. 166(5):675-9. [QxMD MEDLINE Link].
American Thoracic Society/European Respiratory Society statement: standards for the diagnosis and management of individuals with alpha-1 antitrypsin deficiency. Am J Respir Crit Care Med. 2003 Oct 1. 168(7):818-900. [QxMD MEDLINE Link].
[Guideline] US Preventive Services Task Force. Final Update Summary: Tobacco Smoking Cessation in Adults, Including Pregnant Women: Behavioral and Pharmacotherapy Interventions. uspreventiveservicestaskforce.org. Available at https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/tobacco-use-in-adults-and-pregnant-women-counseling-and-interventions1. September 2015; Accessed: December 27, 2017.
Tetley TD. Macrophages and the pathogenesis of COPD. Chest. 2002 May. 121(5 Suppl):156S-159S. [QxMD MEDLINE Link].
Saetta M, Di Stefano A, Turato G, Facchini FM, Corbino L, Mapp CE, et al. CD8+ T-lymphocytes in peripheral airways of smokers with chronic obstructive pulmonary disease. Am J Respir Crit Care Med. 1998 Mar. 157(3 Pt 1):822-6. [QxMD MEDLINE Link].
Luisetti M, Ma S, Iadarola P, Stone PJ, Viglio S, Casado B, et al. Desmosine as a biomarker of elastin degradation in COPD: current status and future directions. Eur Respir J. 2008 Nov. 32(5):1146-57. [QxMD MEDLINE Link].
[Guideline] Sandhaus RA, Turino G, Brantly ML, Campos M, Cross CE, Goodman K, et al. The Diagnosis and Management of Alpha-1 Antitrypsin Deficiency in the Adult. Chronic Obstr Pulm Dis. 2016 Jun 6. 3 (3):668-682. [QxMD MEDLINE Link]. [Full Text].
Hogg JC. Pathophysiology of airflow limitation in chronic obstructive pulmonary disease. Lancet. 2004 Aug 21-27. 364(9435):709-21. [QxMD MEDLINE Link].
Takahashi M, Fukuoka J, Nitta N, Takazakura R, Nagatani Y, Murakami Y. Imaging of pulmonary emphysema: a pictorial review. Int J Chron Obstruct Pulmon Dis. 2008. 3(2):193-204. [QxMD MEDLINE Link].
ATS Committee on Diagnostic Standards for Nontuberculous Respiratory Diseases, American Thoracic Society. Definitions and classification of chronic bronchitis, asthma, and pulmonary emphysema. Am Rev Respir Dis. 1962. 85:762–9.
Finkelstein R, Ma HD, Ghezzo H, Whittaker K, Fraser RS, Cosio MG. Morphometry of small airways in smokers and its relationship to emphysema type and hyperresponsiveness. Am J Respir Crit Care Med. 1995 Jul. 152(1):267-76. [QxMD MEDLINE Link].
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES, Office of the Surgeon General. 2014 Surgeon General's Report: The Health Consequences of Smoking—50 Years of Progress. surgeongeneral.gov. Available at https://www.surgeongeneral.gov/library/reports/50-years-of-progress/full-report.pdf. 2014; Accessed: December 27, 2017.
Crothers K, Butt AA, Gibert CL, Rodriguez-Barradas MC, Crystal S, Justice AC. Increased COPD among HIV-positive compared to HIV-negative veterans. Chest. 2006 Nov. 130(5):1326-33. [QxMD MEDLINE Link].
Buist AS, McBurnie MA, Vollmer WM, Gillespie S, Burney P, Mannino DM, et al. International variation in the prevalence of COPD (the BOLD Study): a population-based prevalence study. Lancet. 2007 Sep 1. 370(9589):741-50. [QxMD MEDLINE Link].
Menezes AM, Perez-Padilla R, Jardim JR, Muino A, Lopez MV, Valdivia G, et al. Chronic obstructive pulmonary disease in five Latin American cities (the PLATINO study): a prevalence study. Lancet. 2005 Nov 26. 366(9500):1875-81. [QxMD MEDLINE Link].
Haruna A, Muro S, Nakano Y, Ohara T, Hoshino Y, Ogawa E, et al. CT scan findings of emphysema predict mortality in COPD. Chest. 2010 Sep. 138(3):635-40. [QxMD MEDLINE Link].
Takei N, Suzuki M, Makita H, et al. Serum alpha-1 antitrypsin levels and the clinical course of chronic obstructive pulmonary disease. Int J Chron Obstruct Pulmon Dis. 2019. 14:2885-93. [QxMD MEDLINE Link]. [Full Text].
[Guideline] Management of Chronic Obstructive Pulmonary Disease Working Group. VA/DoD clinical practice guideline for the management of chronic obstructive pulmonary disease. Washington (DC): Department of Veterans Affairs, Department of Defense; 2014. 94. [Full Text].
[Guideline] Yawn BB, Thomashaw B, Mannino DM, Han MK, Kalhan R, Rennard S, et al. The 2017 Update to the COPD Foundation COPD Pocket Consultant Guide. Chronic Obstr Pulm Dis. 2017 Jul 15. 4 (3):177-185. [QxMD MEDLINE Link]. [Full Text].
[Guideline] Qaseem A, Wilt TJ, Weinberger SE, et al. Diagnosis and management of stable chronic obstructive pulmonary disease: a clinical practice guideline update from the American College of Physicians, American College of Chest Physicians, American Thoracic Society, and European Respiratory Society. Ann Intern Med. 2011 Aug 2. 155 (3):179-91. [QxMD MEDLINE Link]. [Full Text].
COMBIVENT Inhalation Aerosol Study Group. In chronic obstructive pulmonary disease, a combination of ipratropium and albuterol is more effective than either agent alone. An 85-day multicenter trial. COMBIVENT Inhalation Aerosol Study Group. Chest. 1994 May. 105(5):1411-9. [QxMD MEDLINE Link].
Chapman KR, Rennard SI, Dogra A, Owen R, Lassen C, Kramer B. Long-term safety and efficacy of indacaterol, a long-acting beta2-agonist, in subjects with COPD: a randomized, placebo-controlled study. Chest. 2011 Jul. 140(1):68-75. [QxMD MEDLINE Link].
Calverley PM, Anderson JA, Celli B, Ferguson GT, Jenkins C, Jones PW, et al. Salmeterol and fluticasone propionate and survival in chronic obstructive pulmonary disease. N Engl J Med. 2007 Feb 22. 356(8):775-89. [QxMD MEDLINE Link].
O'Donnell DE, Fluge T, Gerken F, Hamilton A, Webb K, Aguilaniu B, et al. Effects of tiotropium on lung hyperinflation, dyspnoea and exercise tolerance in COPD. Eur Respir J. 2004 Jun. 23(6):832-40. [QxMD MEDLINE Link].
Tashkin DP, Celli B, Senn S, Burkhart D, Kesten S, Menjoge S, et al. A 4-year trial of tiotropium in chronic obstructive pulmonary disease. N Engl J Med. 2008 Oct 9. 359(15):1543-54. [QxMD MEDLINE Link].
Brusasco V, Hodder R, Miravitlles M, Korducki L, Towse L, Kesten S. Health outcomes following treatment for six months with once daily tiotropium compared with twice daily salmeterol in patients with COPD. Thorax. 2003 May. 58(5):399-404. [QxMD MEDLINE Link]. [Full Text].
Donohue JF, van Noord JA, Bateman ED, Langley SJ, Lee A, Witek TJ Jr, et al. A 6-month, placebo-controlled study comparing lung function and health status changes in COPD patients treated with tiotropium or salmeterol. Chest. 2002 Jul. 122(1):47-55. [QxMD MEDLINE Link].
Kerwin EM, D'Urzo AD, Gelb AF, Lakkis H, Garcia Gil E, Caracta CF, et al. Efficacy and safety of a 12-week treatment with twice-daily aclidinium bromide in COPD patients (ACCORD COPD I). COPD. 2012 Apr. 9 (2):90-101. [QxMD MEDLINE Link].
Wedzicha JA, Banerji D, Chapman KR, Vestbo J, Roche N, Ayers RT, et al. Indacaterol-Glycopyrronium versus Salmeterol-Fluticasone for COPD. N Engl J Med. 2016 Jun 9. 374 (23):2222-34. [QxMD MEDLINE Link].
Calverley PM, Rabe KF, Goehring UM, Kristiansen S, Fabbri LM, Martinez FJ. Roflumilast in symptomatic chronic obstructive pulmonary disease: two randomised clinical trials. Lancet. 2009 Aug 29. 374(9691):685-94. [QxMD MEDLINE Link].
Wood-Baker RR, Gibson PG, Hannay M, Walters EH, Walters JA. Systemic corticosteroids for acute exacerbations of chronic obstructive pulmonary disease. Cochrane Database Syst Rev. 2005 Jan 25. CD001288. [QxMD MEDLINE Link].
Spencer S, Calverley PM, Burge PS, Jones PW. Impact of preventing exacerbations on deterioration of health status in COPD. Eur Respir J. 2004 May. 23(5):698-702. [QxMD MEDLINE Link].
Walters JA, Walters EH, Wood-Baker R. Oral corticosteroids for stable chronic obstructive pulmonary disease. Cochrane Database Syst Rev. 2005 Jul 20. CD005374. [QxMD MEDLINE Link].
Sin DD, Tashkin D, Zhang X, Radner F, Sjobring U, Thorén A, et al. Budesonide and the risk of pneumonia: a meta-analysis of individual patient data. Lancet. 2009 Aug 29. 374(9691):712-9. [QxMD MEDLINE Link].
Vestbo J, Anderson JA, Brook RD, Calverley PM, Celli BR, Crim C, et al. Fluticasone furoate and vilanterol and survival in chronic obstructive pulmonary disease with heightened cardiovascular risk (SUMMIT): a double-blind randomised controlled trial. Lancet. 2016 Apr 30. 387 (10030):1817-26. [QxMD MEDLINE Link].
Albert RK, Connett J, Bailey WC, Casaburi R, Cooper JA Jr, Criner GJ, et al. Azithromycin for prevention of exacerbations of COPD. N Engl J Med. 2011 Aug 25. 365(8):689-98. [QxMD MEDLINE Link]. [Full Text].
Petty TL. The National Mucolytic Study. Results of a randomized, double-blind, placebo-controlled study of iodinated glycerol in chronic obstructive bronchitis. Chest. 1990 Jan. 97(1):75-83. [QxMD MEDLINE Link].
Zheng JP, Wen FQ, Bai CX, Wan HY, Kang J, Chen P, et al. Twice daily N-acetylcysteine 600 mg for exacerbations of chronic obstructive pulmonary disease (PANTHEON): a randomised, double-blind placebo-controlled trial. Lancet Respir Med. 2014 Mar. 2(3):187-94. [QxMD MEDLINE Link].
Sasaki T, Nakayama K, Yasuda H, Yoshida M, Asamura T, Ohrui T, et al. A randomized, single-blind study of lansoprazole for the prevention of exacerbations of chronic obstructive pulmonary disease in older patients. J Am Geriatr Soc. 2009 Aug. 57(8):1453-7. [QxMD MEDLINE Link].
Nocturnal Oxygen Therapy Trial Group. Continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive lung disease: a clinical trial. Nocturnal Oxygen Therapy Trial Group. Ann Intern Med. 1980 Sep. 93(3):391-8. [QxMD MEDLINE Link].
Moberley S, Holden J, Tatham DP, Andrews RM. Vaccines for preventing pneumococcal infection in adults. Cochrane Database Syst Rev. 2013 Jan 31. 1:CD000422. [QxMD MEDLINE Link].
Kyaw MH, Clarke S, Edwards GF, Jones IG, Campbell H. Serotypes/groups distribution and antimicrobial resistance of invasive pneumococcal isolates: implications for vaccine strategies. Epidemiol Infect. 2000 Dec. 125(3):561-72. [QxMD MEDLINE Link].
[Guideline] Centers for Disease Control and Prevention. Updated recommendations for prevention of invasive pneumococcal disease among adults using the 23-valent pneumococcal polysaccharide vaccine (PPSV23). MMWR Morb Mortal Wkly Rep. 2010 Sep 3. 59(34):1102-6. [QxMD MEDLINE Link]. [Full Text].
Hubbard RC, Crystal RG. Augmentation therapy of alpha 1-antitrypsin deficiency. Eur Respir J Suppl. 1990 Mar. 9:44s-52s. [QxMD MEDLINE Link].
Hurst JR, Donaldson GC, Quint JK, Goldring JJ, Baghai-Ravary R, Wedzicha JA. Temporal clustering of exacerbations in chronic obstructive pulmonary disease. Am J Respir Crit Care Med. 2009 Mar 1. 179(5):369-74. [QxMD MEDLINE Link].
O'Donnell DE, Parker CM. COPD exacerbations . 3: Pathophysiology. Thorax. 2006 Apr. 61(4):354-61. [QxMD MEDLINE Link]. [Full Text].
Lightowler JV, Wedzicha JA, Elliott MW, Ram FS. Non-invasive positive pressure ventilation to treat respiratory failure resulting from exacerbations of chronic obstructive pulmonary disease: Cochrane systematic review and meta-analysis. BMJ. 2003 Jan 25. 326(7382):185. [QxMD MEDLINE Link]. [Full Text].
Naunheim KS, Wood DE, Mohsenifar Z, Sternberg AL, Criner GJ, DeCamp MM, et al. Long-term follow-up of patients receiving lung-volume-reduction surgery versus medical therapy for severe emphysema by the National Emphysema Treatment Trial Research Group. Ann Thorac Surg. 2006 Aug. 82(2):431-43. [QxMD MEDLINE Link].
Sciurba FC, Ernst A, Herth FJ, Strange C, Criner GJ, Marquette CH, et al. A randomized study of endobronchial valves for advanced emphysema. N Engl J Med. 2010 Sep 23. 363(13):1233-44. [QxMD MEDLINE Link].
Celli BR, Cote CG, Marin JM, Casanova C, Montes de Oca M, Mendez RA, et al. The body-mass index, airflow obstruction, dyspnea, and exercise capacity index in chronic obstructive pulmonary disease. N Engl J Med. 2004 Mar 4. 350(10):1005-12. [QxMD MEDLINE Link].
Rochester CL, Vogiatzis I, Holland AE, et al. An Official American Thoracic Society/European Respiratory Society Policy Statement: Enhancing Implementation, Use, and Delivery of Pulmonary Rehabilitation. Am J Respir Crit Care Med. 2015 Dec 1. 192 (11):1373-86. [QxMD MEDLINE Link]. [Full Text].
Spruit MA, Singh SJ, Garvey C, et al. An official American Thoracic Society/European Respiratory Society statement: key concepts and advances in pulmonary rehabilitation. Am J Respir Crit Care Med. 2013 Oct 15. 188 (8):e13-64. [QxMD MEDLINE Link]. [Full Text].
Creutzberg EC, Wouters EF, Mostert R, Pluymers RJ, Schols AM. A role for anabolic steroids in the rehabilitation of patients with COPD? A double-blind, placebo-controlled, randomized trial. Chest. 2003 Nov. 124(5):1733-42. [QxMD MEDLINE Link].
[Guideline] Wedzicha JA Ers Co-Chair, Miravitlles M, Hurst JR, Calverley PM, Albert RK, Anzueto A, et al. Management of COPD exacerbations: a European Respiratory Society/American Thoracic Society guideline. Eur Respir J. 2017 Mar. 49 (3):[QxMD MEDLINE Link]. [Full Text].
[Guideline] Criner GJ, Bourbeau J, Diekemper RL, et al. Prevention of acute exacerbations of COPD: American College of Chest Physicians and Canadian Thoracic Society Guideline. Chest. 2015 Apr. 147 (4):894-942. [QxMD MEDLINE Link]. [Full Text].
[Guideline] Wedzicha JA, Calverley PMA, Albert RK, Anzueto A, Criner GJ, Hurst JR, et al. Prevention of COPD exacerbations: a European Respiratory Society/American Thoracic Society guideline. Eur Respir J. 2017 Sep. 50 (3):[QxMD MEDLINE Link]. [Full Text].
[Guideline] Bolton CE, Bevan-Smith EF, Blakey JD, et al. British Thoracic Society guideline on pulmonary rehabilitation in adults. Thorax. 2013 Sep. 68 Suppl 2:ii1-30. [QxMD MEDLINE Link]. [Full Text].
Leung KM, Curran-Everett D, Regan EA, Lynch DA, Jacobson FL. Translation of adapting quantitative CT data from research to local clinical practice: validation evaluation of fully automated procedures to provide lung volumes and percent emphysema. J Med Imaging (Bellingham). 2020 Mar. 7 (2):022404. [QxMD MEDLINE Link].
Henkel M, Partyka J, Gregory AD, et al. Follistatin-like 1 attenuation causes spontaneous smoke-resistant pulmonary emphysema. Am J Respir Crit Care Med. 2019 Dec 13. [QxMD MEDLINE Link].
Li K, Gao Y, Pan Z, et al. Influence of emphysema and air trapping heterogeneity on pulmonary function in patients with COPD. Int J Chron Obstruct Pulmon Dis. 2019. 14:2863-72. [QxMD MEDLINE Link]. [Full Text].

Media Gallery

Emphysema. Gross pathology of bullous emphysema shows bullae on the surface of the lungs.
Emphysema. Gross pathology of emphysema shows bullae on the lung surface.
Emphysema. At high magnification, loss of airway walls and dilated airspaces are observed in emphysema.
Emphysema. This chest radiograph shows hyperinflation, flattened diaphragms, increased retrosternal space, and hyperlucency of the lung parenchyma in emphysema.
Emphysema. A computed tomography scan shows emphysematous bullae in the upper lobes.
Emphysema. Diffuse emphysema secondary to cigarette smoking.
Emphysema. A pressure-volume curve is drawn for a patient with restrictive lung disease and obstructive disease and is compared to healthy lungs.
Emphysema. A flow-volume curve of lungs with emphysema shows a marked decrease in expiratory flows, hyperinflation, and air trapping (patient B) compared to a patient with restrictive lung disease, who has reduced lung volumes and preserved flows (patient A).
Emphysema. Forced expiratory volume in 1 second (FEV1) can be used to evaluate the prognosis in patients with emphysema. The benefit of smoking cessation is shown here because the deterioration in lung function parallels that of a nonsmoker, even in late stages of the disease.
Emphysema. A computed tomograph scan showing severe emphysema and bullous disease.
Emphysema. An emphysematous lung shows an increased anteroposterior (AP) diameter, increased retrosternal airspace, and flattened diaphragms on posteroanterior (PA) film.
Emphysema. An emphysematous lung shows an increased anteroposterior (AP) diameter, increased retrosternal airspace, and flattened diaphragms on a lateral chest radiograph.
Emphysema. The differential diagnosis of a unilateral hyperlucent lung includes pulmonary arterial hypoplasia and Swyer-James syndrome. The expiratory chest radiograph exhibits evidence of air trapping and is helpful in making the diagnosis. Swyer-James syndrome is unilateral bronchiolitis obliterans, which develops during early childhood.
Emphysema. A lateral chest radiograph of Swyer-James syndrome may demonstrate some of the features of emphysema.
Emphysema. Paraseptal emphysema. Courtesy of Dr Frank Gaillard, Radiopaedia.org (http://radiopaedia.org/cases/emphysema-diagrams).
Emphysema. Panlobular emphysema. Courtesy of Dr Frank Gaillard, Radiopaedia.org (http://radiopaedia.org/cases/emphysema-diagrams).
Emphysema. Centrilobular emphysema. Courtesy of Dr Frank Gaillard, Radiopaedia.org (http://radiopaedia.org/cases/emphysema-diagrams).
Emphysema. Early stethoscope drawing circa 1819. From Wikipedia.
Emphysema. Laennec's early stethoscope made of brass and wood circa 1820. From Wikipedia.

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Author

Kamran Boka, MD, MS Attending Physician in Pulmonary and Critical Care Medicine, StatCare

Kamran Boka, MD, MS is a member of the following medical societies: American College of Critical Care Medicine, Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

Daniel R Ouellette, MD, FCCP Associate Professor of Medicine, Wayne State University School of Medicine; Medical Director, Pulmonary Medicine General Practice Unit (F2), Senior Staff and Attending Physician, Division of Pulmonary and Critical Care Medicine, Henry Ford Hospital

Daniel R Ouellette, MD, FCCP is a member of the following medical societies: American College of Chest Physicians, American Thoracic Society, Society of Critical Care Medicine

Disclosure: Received research grant from: Sanofi Pharmaceutical.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Zab Mosenifar, MD, FACP, FCCP Geri and Richard Brawerman Chair in Pulmonary and Critical Care Medicine, Professor and Executive Vice Chairman, Department of Medicine, Medical Director, Women's Guild Lung Institute, Cedars Sinai Medical Center, University of California, Los Angeles, David Geffen School of Medicine

Zab Mosenifar, MD, FACP, FCCP is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, American Thoracic Society

Disclosure: Nothing to disclose.

Additional Contributors

Helen M Hollingsworth, MD Director, Adult Asthma and Allergy Services, Associate Professor, Department of Internal Medicine, Division of Pulmonary and Critical Care, Boston Medical Center

Helen M Hollingsworth, MD is a member of the following medical societies: American Academy of Allergy Asthma and Immunology, American College of Chest Physicians, American Thoracic Society, Massachusetts Medical Society

Disclosure: Nothing to disclose.

Acknowledgements

Berj George Demirjian, MD Fellow, Division of Pulmonary/Critical Care Medicine, Cedars-Sinai Medical Center

Berj George Demirjian, MD is a member of the following medical societies: American College of Chest Physicians, American Medical Association, California Medical Association, California Thoracic Society, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Nader Kamangar, MD, FACP, FCCP, FCCM Associate Professor of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of California, Los Angeles, David Geffen School of Medicine, Olive View-UCLA Medical Center; Associate Program Director, Pulmonary and Critical Care Multi-Campus Fellowship Program, Cedars-Sinai/West Los Angeles Veterans Affairs/Los Angeles Kaiser Permanente/Olive View-UCLA Medical Center; Site Director, Pulmonary/Critical Care Fellowship Program, Olive View-UCLA Medical Center

Nader Kamangar, MD, FACP, FCCP, FCCM is a member of the following medical societies: American Academy of Sleep Medicine, American Association of Bronchology, American College of Chest Physicians, American College of Physicians, American Lung Association, American Medical Association, American Thoracic Society, California Thoracic Society, and Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Sat Sharma, MD, FRCPC Professor and Head, Division of Pulmonary Medicine, Department of Internal Medicine, University of Manitoba; Site Director, Respiratory Medicine, St Boniface General Hospital

Sat Sharma, MD, FRCPC is a member of the following medical societies: American Academy of Sleep Medicine, American College of Chest Physicians, American College of Physicians-American Society of Internal Medicine, American Thoracic Society, Canadian Medical Association, Royal College of Physicians and Surgeons of Canada, Royal Society of Medicine, Society of Critical Care Medicine, and World Medical Association

Disclosure: Nothing to disclose.