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At the time the article was created Bruno Di Muzio had no recorded disclosures.View Bruno Di Muzio's current disclosures
At the time the article was last revised Henry Knipe had the following disclosures:
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Air trapping in chest imaging refers to retention of excess gas (“air”) in all or part of the lung, especially during expiration, either as a result of complete or partial airway obstruction or as a result of local abnormalities in pulmonary compliance. It may also sometimes be observed in normal individuals 3.
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Although not in common usage, the term gas trapping is more accurate ref.
Air trapping is common, occurring in ~50% of CT thorax examinations 6.
Mild (<25% parenchyma) air trapping may be asymptomatic or clinically insignificant 6.
The presence of air trapping can arise from a number of causes (the mnemonic HSBC can be used to help remember these) but usually suggests airway disease (often small airways disease). Air trapping can occur in isolation, or in association with bronchiectasis, interstitial lung disease, or rarely tree-in-bud opacity, which can help narrow the etiology 3,6:
high BMI / obesity 12,13
maybe due to reduced chest wall compliance prompting a rapid, shallow breathing pattern
Other uncommon conditions include 5,6:
neuroendocrine cell proliferation spectrum
diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) 7
scoliosis: especially when severe
Air trapping is a descriptor used in lung CT seen as a decreased attenuation of pulmonary parenchyma, especially manifested as a less than normal increase in attenuation during expiratory acquisition. This appearance must be differentiated from the decreased attenuation of hypoperfusion secondary to locally increased pulmonary arterial resistance 1.
The concurrent presence of absence or bronchiectasis and interstitial lung disease may be useful to narrow the differential possibilities 10.
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- 2. Wayne Richard Webb, Nestor Luiz Müller, David P. Naidich. High-Resolution CT of the Lung. (2009) ISBN: 0781769094 - Google Books
- 3. Tanaka N, Matsumoto T, Miura G et al. Air Trapping at CT: High Prevalence in Asymptomatic Subjects with Normal Pulmonary Function. Radiology. 2003;227(3):776-85. doi:10.1148/radiol.2273020352 - Pubmed
- 4. Arakawa H & Webb W. Air Trapping on Expiratory High-Resolution CT Scans in the Absence of Inspiratory Scan Abnormalities: Correlation with Pulmonary Function Tests and Differential Diagnosis. AJR Am J Roentgenol. 1998;170(5):1349-53. doi:10.2214/ajr.170.5.9574614 - Pubmed
- 5. Tsiligiannis T & Grivas T. Pulmonary Function in Children with Idiopathic Scoliosis. Scoliosis. 2012;7(1):7. doi:10.1186/1748-7161-7-7 - Pubmed
- 6. Miller W, Chatzkel J, Hewitt M. Expiratory Air Trapping on Thoracic Computed Tomography. A Diagnostic Subclassification. Annals ATS. 2014;11(6):874-81. doi:10.1513/annalsats.201311-390oc
- 7. Benson R, Rosado-de-Christenson M, Martínez-Jiménez S, Kunin J, Pettavel P. Spectrum of Pulmonary Neuroendocrine Proliferations and Neoplasms. Radiographics. 2013;33(6):1631-49. doi:10.1148/rg.336135506 - Pubmed
- 8. Mets O, van Hulst R, Jacobs C, van Ginneken B, de Jong P. Normal Range of Emphysema and Air Trapping on CT in Young Men. AJR Am J Roentgenol. 2012;199(2):336-40. doi:10.2214/ajr.11.7808
- 9. Lucidarme O, Grenier P, Cadi M, Mourey-Gerosa I, Benali K, Cluzel P. Evaluation of Air Trapping at CT: Comparison of Continuous- Versus Suspended-Expiration CT Techniques. Radiology. 2000;216(3):768-72. doi:10.1148/radiology.216.3.r00se21768 - Pubmed
- 10. Miller W, Chatzkel J, Hewitt M. Expiratory Air Trapping on Thoracic Computed Tomography. A Diagnostic Subclassification. Annals ATS. 2014;11(6):874-81. doi:10.1513/annalsats.201311-390oc
- 11. Mohamed Hoesein F & de Jong P. Air Trapping on Computed Tomography: Regional versus Diffuse. Eur Respir J. 2017;49(1):1601791. doi:10.1183/13993003.01791-2016 - Pubmed
- 12. Costa D, Barbalho M, Miguel G, Forti E, Azevedo J. The Impact of Obesity on Pulmonary Function in Adult Women. Clinics. 2008;63(6):719-24. doi:10.1590/s1807-59322008000600002 - Pubmed
- 13. Parameswaran K, Todd D, Soth M. Altered Respiratory Physiology in Obesity. Can Respir J. 2006;13(4):203-10. doi:10.1155/2006/834786 - Pubmed