eMedicine Specialties > Radiology > Chest

Acute Respiratory Distress Syndrome

Author: Kenneth T Horlander, MD, Consulting Staff, Department of Pulmonary and Critical Care Medicine, West Georgia Health System and Emory Clark-Holder Clinic
Coauthor(s): James Gruden, MD, Consulting Staff, Department of Radiology, Mayo Clinic of Scottsdale
Contributor Information and Disclosures

Updated: Aug 13, 2008

Introduction

Background

Acute respiratory distress syndrome (ARDS) was first described by Ashbaugh and colleagues in 1967.1 The authors reported the condition as an acute onset of severe respiratory distress, cyanosis (hypoxemia) that is refractory to oxygen therapy, diffuse abnormalities on chest radiographs (CXRs), and decreased lung compliance. In 1994, the American-European Consensus Conference (AECC) on ARDS formulated their definition of ARDS as follows2 :

  • Acute onset of symptoms
  • The ratio of the alveolar partial pressure of oxygen (PaO2) to the fraction of inspired oxygen (FIO2) of 200 mm Hg or less
  • Bilateral infiltrates on CXRs
  • Pulmonary arterial wedge pressure of 18 mm Hg or less or no clinical signs of left atrial hypertension

The radiographic abnormalities of ARDS reflect the leakage of fluid with a high protein content into the alveolar spaces because of alveolar epithelial injury, or diffuse alveolar damage. ARDS is a syndrome that is defined by its clinical features. The condition may result from intrathoracic or extrathoracic events of various etiologies, such as inflammatory, infectious, vascular, or traumatic etiologies. Determining the causative event may be clinically important for proper treatment.3,4,5,6,7

ARDS is a syndrome that commonly begins after exposure to a known risk factor. Why some people develop ARDS and others do not is still unknown. The risk factors for ARDS include primary pulmonary etiologies (eg, aspiration, pneumonia, toxic inhalation, pulmonary contusion) and extrapulmonary etiologies (eg, sepsis, pancreatitis, multiple blood transfusions, trauma, use of drugs such as heroin). Sometimes, ARDS is not only a reaction to another event but also the result of a known cause, such as an acute interstitial pneumonia (AIP) or a severe, extensive, infectious pneumonia.

For excellent patient education resources, visit eMedicine's Lung and Airway Center. Also, see eMedicine's patient education article Acute Respiratory Distress Syndrome.

Related eMedicine articles:
Aspiration Pneumonia
CBRNE - Lung-Damaging Agents, Toxic Smokes: NOx, HC, RP, FS, FM, SGF2, Teflon
Children's Interstitial Lung Disease (ChILD)
Pneumonia, Typical Bacterial

Related Medscape topics:
Mortality Rates for Patients With Acute Lung Injury/ARDS Have Decreased Over Time
CME/CE  NIH/ARDS Network Fluid Management Trial (The FACTT Study)
CME  ATS 2008: Managing Acute Respiratory Failure


Pathophysiology

The diagnostic criterion standard for acute respiratory distress syndrome (ARDS) is pathologic evidence of diffuse alveolar damage that has been obtained from lung tissue via biopsy. However, biopsy may not be possible because of the patient's clinical condition. If a biopsy is performed, ARDS can be categorized by its pathologic phases, which are similar regardless of the cause of ARDS. The pathologic findings often follow a similar time course, but this can vary between patients. The ARDS phases are as follows:

  • The exudative phase occurs within hours after the initial pulmonary insult and usually lasts 2-7 days. At this early stage of ARDS, the clinical findings are correlated with the microscopic findings of hyaline membranes, loss of the alveolar epithelium, edema, and hemorrhage (see Image 5).
  • The proliferative phase, which usually occurs 7-28 days after the initial pulmonary insult, follows the exudative phase. In this early proliferative phase, type 2 pneumocytic proliferation is present, along with widening of the septa and interstitial fibroblast proliferation (see Image 6).
  • The late proliferative, or fibrotic, phase of ARDS is the result of cellular proliferation that leads to the deposition of collagen and proteoglycans. Extensive fibroblast proliferation with incorporation of the hyaline membranes is a characteristic finding in this stage of ARDS (see Image 7).
  • Interstitial fibrosis develops in some patients. Pulmonary vascular abnormalities are common, such as microvascular thrombi and vascular remodeling.

Frequency

United States

The annual incidence of acute respiratory distress syndrome (ARDS) has been reported to be 150,000 cases; however, this number is suspect because of differing definitions for ARDS. Previously, the National Institutes of Health (NIH) Acute Respiratory Distress Syndrome Network enrolled many ARDS patients into clinical trials. The ARDS incidence rate estimates from those trials agreed with an earlier NIH estimate of 75 cases per 100,000 persons per year.

International

The incidence for acute respiratory distress syndrome (ARDS) is about 18 cases per 100,000 persons per year for acute lung injury (ALI) and 13.5 cases per 100,000 persons per year for ARDS, as reported by the Acute Respiratory Failure (ARF) Study Group in Sweden, Denmark, and Iceland.8

Mortality/Morbidity

Mortality in acute respiratory distress syndrome (ARDS) is commonly secondary to multiorgan dysfunction. Less alveolar epithelial damage indicates a better likelihood of the patient recovering pulmonary function.9,10

Differential Diagnoses

Aspiration Pneumonia
Congestive Heart Failure
Pneumonia, Atypical Bacterial
Pneumonia, Pneumocystis Carinii
Pneumonia, Typical Bacterial
Pneumonia, Viral

Other Problems to Be Considered

Diffuse pneumonia of any origin (although pneumonia can be a cause of ARDS)
Cardiogenic edema
Massive aspiration (although aspiration, too, can be a cause of ARDS)
Pulmonary hemorrhage
Severe acute respiratory syndrome (SARS)

Congestive heart failure (CHF) can mimic ARDS. A Swan-Ganz catheter is used to measure the left ventricular end-diastolic pressure to rule out CHF. According to the AECC definition, the pulmonary artery wedge pressure (pulmonary artery occlusion pressure) for ARDS, as measured with a Swan-Ganz catheter, should be 18 mm Hg or less.

Some investigators believe that distinguishing CHF from ARDS may be difficult and arbitrary at times, and they propose a classification for permeability edema. The 4 categories are as follows: (1) hydrostatic edema, (2) permeability edema due to diffuse alveolar damage or ARDS, (3) permeability edema without diffuse alveolar damage, or (4) mixed (hydrostatic and permeability edema).11

The cause of ARDS is commonly an immune reaction to an otherwise nonrelated event; other times, the condition results from a direct insult to the lung that causes pathologically identical changes as ARDS. This is the case for diffuse pneumonias of any origin and is commonly seen with viral pneumonia. SARS is a good example of a probable infectious pneumonia that is ARDS, pathologically and clinically. Experts have speculated that the cause is from a coronavirus that may be transmitted via respiratory secretions and develops after 2-11 days of a febrile illness.

More on Acute Respiratory Distress Syndrome

Overview: Acute Respiratory Distress Syndrome
Imaging: Acute Respiratory Distress Syndrome
Multimedia: Acute Respiratory Distress Syndrome
References
[ CLOSE WINDOW ]

References

  1. Ashbaugh DG, Bigelow DB, Petty TL, Levine BE. Acute respiratory distress in adults. Lancet. Aug 12 1967;2(7511):319-23. [Medline].

  2. Bernard GR, Artigas A, Brigham KL, et al. The American-European Consensus Conference on ARDS. Definitions, mechanisms, relevant outcomes, and clinical trial coordination. Am J Respir Crit Care Med. Mar 1994;149(3 pt 1):818-24. [Medline].

  3. Kazerooni EA, Pranikoff T, Cascade PN, Hirschl RB. Partial liquid ventilation with perflubron during extracorporeal life support in adults: radiographic appearance. Radiology. Jan 1996;198(1):137-42. [Medline]. [Full Text].

  4. Rotta AT, Gunnarsson B, Hernan LJ, Fuhrman BP, Steinhorn DM. Partial liquid ventilation with perflubron attenuates in vivo oxidative damage to proteins and lipids. Crit Care Med. Jan 2000;28(1):202-8. [Medline].

  5. Toro-Figueroa LO, Meliones JN, Thompson AE. Perflubron partial liquid ventilation in children with ARDS: a safety and efficacy pilot study (abstract). Crit Care Med. 1996;24:a150.

  6. Muellenbach RM, Kredel M, Wunder C, Küstermann J, Wurmb T, Schwemmer U, et al. Arteriovenous extracorporeal lung assist as integral part of a multimodal treatment concept: a retrospective analysis of 22 patients with ARDS refractory to standard care. Eur J Anaesthesiol. Jul 29 2008;1-8. [Medline].

  7. [Best Evidence] Peter JV, John P, Graham PL, Moran JL, George IA, Bersten A. Corticosteroids in the prevention and treatment of acute respiratory distress syndrome (ARDS) in adults: meta-analysis. BMJ. May 3 2008;336(7651):1006-9. [Medline].

  8. Luhr OR, Antonsen K, Karlsson M, et al. Incidence and mortality after acute respiratory failure and acute respiratory distress syndrome in Sweden, Denmark, and Iceland. The ARF Study Group. Am J Respir Crit Care Med. Jun 1999;159(6):1849-61. [Medline]. [Full Text].

  9. Zambon M, Vincent JL. Mortality rates for patients with acute lung injury/ARDS have decreased over time. Chest. May 2008;133(5):1120-7. [Medline].

  10. [Best Evidence] Agarwal R, Srinivas R, Nath A, Jindal SK. Is the mortality higher in the pulmonary vs the extrapulmonary ARDS? A meta analysis. Chest. Jun 2008;133(6):1463-73. [Medline].

  11. Ketai LH, Godwin JD. A new view of pulmonary edema and acute respiratory distress syndrome. J Thorac Imaging. Jul 1998;13(3):147-71. [Medline].

  12. Johnson TH, Tytle TL, Cooke RE. Adult respiratory distress syndrome: radiologic manifestations and course. South Med J. Sep 1984;77(9):1136-8. [Medline].

  13. Wakabayashi T, Tamura M, Nakamura T. Partial liquid ventilation with low-dose perfluorochemical and high-frequency oscillation improves oxygenation and lung compliance in a rabbit model of surfactant depletion. Biol Neonate. 2006;89(3):177-82. [Medline].

  14. Ricard JD, Iserin F, Dreyfuss D, Saumon G. Perflubron dosing affects ventilator-induced lung injury in rats with previous lung injury. Crit Care Med. Feb 2007;35(2):561-7. [Medline].

  15. Hirschl RB, Pranikoff T, Wise C, et al. Initial experience with partial liquid ventilation in adult patients with the acute respiratory distress syndrome. JAMA. Feb 7 1996;275(5):383-9. [Medline].

  16. Leach CL, Greenspan JS, Rubenstein SD, et al. Partial liquid ventilation with perflubron in premature infants with severe respiratory distress syndrome. The LiquiVent Study Group. N Engl J Med. Sep 12 1996;335(11):761-7. [Medline].

  17. Johnson TH, Altman AR, McCaffree RD. Radiologic considerations in the adult respiratory distress syndrome treated with positive end expiratory pressure (PEEP). Clin Chest Med. Jan 1982;3(1):89-100. [Medline].

  18. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. May 4 2000;342(18):1301-8. [Medline].

  19. Tagliabue M, Casella TC, Zincone GE, Fumagalli R, Salvini E. CT and chest radiography in the evaluation of adult respiratory distress syndrome. Acta Radiol. May 1994;35(3):230-4. [Medline].

  20. Caironi P, Carlesso E, Gattinoni L. Radiological imaging in acute lung injury and acute respiratory distress syndrome. Semin Respir Crit Care Med. Aug 2006;27(4):404-15. [Medline].

  21. Easley RB, Fuld MK, Fernandez-Bustamante A, Hoffman EA, Simon BA. Mechanism of hypoxemia in acute lung injury evaluated by multidetector-row CT. Acad Radiol. Jul 2006;13(7):916-21. [Medline].

  22. Ketai L, Paul NS, Wong KT. Radiology of severe acute respiratory syndrome (SARS): the emerging pathologic-radiologic correlates of an emerging disease. J Thorac Imaging. Nov 2006;21(4):276-83. [Medline].

  23. Helm E, Talakoub O, Grasso F, Engelberts D, Alirezaie J, Kavanagh BP, et al. Use of dynamic CT in acute respiratory distress syndrome (ARDS) with comparison of positive and negative pressure ventilation. Eur Radiol. Jul 24 2008;[Medline].

  24. Tomiyama N, Müller NL, Johkoh T, et al. Acute respiratory distress syndrome and acute interstitial pneumonia: comparison of thin-section CT findings. J Comput Assist Tomogr. Jan-Feb 2001;25(1):28-33. [Medline].

  25. van der Werf TS, Wolf RF, Tulleken JE, Ligtenberg JJ, Zijlstra JG. The vanishing heart--deterioration on chest radiography with clinical improvement during prone position ventilation. Br J Radiol. Apr 1998;71(844):447-9. [Medline]. [Full Text].

  26. Papazian L, Paladini MH, Bregeon F, et al. Can the tomographic aspect characteristics of patients presenting with acute respiratory distress syndrome predict improvement in oxygenation-related response to the prone position?. Anesthesiology. Sep 2002;97(3):599-607. [Medline].

  27. Nöbauer-Huhmann IM, Eibenberger K, Schaefer-Prokop C, et al. Changes in lung parenchyma after acute respiratory distress syndrome (ARDS): assessment with high-resolution computed tomography. Eur Radiol. 2001;11(12):2436-43. [Medline].

  28. Musch G, Venegas JG. Positron emission tomography imaging of regional lung function. Minerva Anestesiol. Jun 2006;72(6):363-7. [Medline]. [Full Text].

  29. Richard JC, Le Bars D, Costes N, et al. Alveolar recruitment assessed by positron emission tomography during experimental acute lung injury. Intensive Care Med. Nov 2006;32(11):1889-94. [Medline].

  30. Goss CH, Brower RG, Hudson LD, Rubenfeld GD. Incidence of acute lung injury in the United States. Crit Care Med. Jun 2003;31(6):1607-11. [Medline].

  31. Hirschl RB, Tooley R, Parent A, Johnson K, Bartlett RH. Evaluation of gas exchange, pulmonary compliance, and lung injury during total and partial liquid ventilation in the acute respiratory distress syndrome. Crit Care Med. Jun 1996;24(6):1001-8. [Medline].

  32. McLoud TC, Barash PG, Ravin CE. PEEP: radiographic features and associated complications. AJR Am J Roentgenol. Aug 1977;129(2):209-13. [Medline]. [Full Text].

  33. Meduri GU, Headley AS, Golden E, et al. Effect of prolonged methylprednisolone therapy in unresolving acute respiratory distress syndrome: a randomized controlled trial. JAMA. Jul 8 1998;280(2):159-65. [Medline].

  34. Mäurer J, Kendzia A, Gerlach H, et al. Morphological changes in chest radiographs of patients with acute respiratory distress syndrome (ARDS). Intensive Care Med. Nov 1998;24(11):1152-6. [Medline].

  35. Tsang KW, Ho PL, Ooi GC, et al. A cluster of cases of severe acute respiratory syndrome in Hong Kong. N Engl J Med. May 15 2003;348(20):1977-85. [Medline].

  36. Wheeler AP, Carroll FE, Bernard GR. Radiographic issues in adult respiratory distress syndrome. New Horiz. Nov 1993;1(4):471-7. [Medline].

[ CLOSE WINDOW ]

Further Reading

[ CLOSE WINDOW ]

Keywords

ARDS, acute respiratory distress syndrome, adult respiratory distress syndrome, pulmonary insufficiency, lung disease, respiratory tract disease, respiratory failure, respiratory syndrome, respiratory distress syndrome, severe respiratory distress, cyanosis, hypoxemia, diffuse alveolar damage, acute lung injury, ALI

[ CLOSE WINDOW ]

Contributor Information and Disclosures

Author

Kenneth T Horlander, MD, Consulting Staff, Department of Pulmonary and Critical Care Medicine, West Georgia Health System and Emory Clark-Holder Clinic
Kenneth T Horlander, MD is a member of the following medical societies: American College of Chest Physicians, American Thoracic Society, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

James Gruden, MD, Consulting Staff, Department of Radiology, Mayo Clinic of Scottsdale
James Gruden, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Chest Physicians, American College of Radiology, American Medical Association, American Roentgen Ray Society, American Thoracic Society, Radiological Society of North America, Society for Health Services Research in Radiology, and Society of Thoracic Radiology
Disclosure: Nothing to disclose.

Medical Editor

Judith K Amorosa, MD, FACR, Clinical Professor and Program Director, Department of Radiology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School; Consulting Staff, Department of Radiology, Robert Wood Johnson University Hospital
Judith K Amorosa, MD, FACR is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, Association of University Radiologists, Radiological Society of North America, and Society of Thoracic Radiology
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Eric J Stern, MD, Professor of Radiology, Adjunct Professor of Medicine, Adjunct Professor of Medical Education and Biomedical Informatics, University of Washington School of Medicine; Director of Thoracic Imaging, Harborview Medical Center; Associate Medical Staff, Seattle Cancer Care Alliance
Eric J Stern, MD is a member of the following medical societies: American Roentgen Ray Society, Association of University Radiologists, European Society of Radiology, Radiological Society of North America, and Society of Thoracic Radiology
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

Eugene C Lin, MD, Clinical Assistant Professor of Radiology, University of Washington Medical School
Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, and Society of Nuclear Medicine
Disclosure: Nothing to disclose.

 
 
HONcode

We subscribe to the
HONcode principles of the
Health On the Net Foundation

All material on this website is protected by copyright, Copyright© 1994- by Medscape.
This website also contains material copyrighted by 3rd parties.

DISCLAIMER: The content of this Website is not influenced by sponsors. The site is designed primarily for use by qualified physicians and other medical professionals. The information contained herein should NOT be used as a substitute for the advice of an appropriately qualified and licensed physician or other health care provider. The information provided here is for educational and informational purposes only. In no way should it be considered as offering medical advice. Please check with a physician if you suspect you are ill.