Air trapping, also called gas trapping, is an abnormal retention of air in the

lungs The lungs are the primary organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the backbone on either side of the heart. Their function in the respiratory syste ...

where it is difficult to exhale completely. It is observed in

obstructive lung disease Obstructive lung disease is a category of respiratory disease characterized by airway obstruction. Many obstructive diseases of the lung result from narrowing (obstruction) of the smaller bronchi and larger bronchioles, often because of excessiv ...

s such as

asthma Asthma is a common long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wh ...

, bronchiolitis obliterans syndrome and

chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by chronic respiratory symptoms and airflow limitation. GOLD defines COPD as a heterogeneous lung condition characterized by chronic respiratory s ...

s such as

emphysema Emphysema is any air-filled enlargement in the body's tissues. Most commonly emphysema refers to the permanent enlargement of air spaces (alveoli) in the lungs, and is also known as pulmonary emphysema. Emphysema is a lower respiratory tract di ...

and

chronic bronchitis Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...

. Air trapping is not a diagnosis but is a presentation of an illness, and can be a guide to the appropriate

differential diagnosis In healthcare, a differential diagnosis (DDx) is a method of analysis that distinguishes a particular disease or condition from others that present with similar clinical features. Differential diagnostic procedures are used by clinicians to di ...

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Imaging

Measurement and function

Exhaled volumes are measured by a pulmonary function test or simple

spirometry Spirometry (meaning ''the measuring of breath'') is the most common of the pulmonary function tests (PFTs). It measures lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. Spirometry is h ...

, leading to an elevated residual volume and a measurement of forced expiratory volume. Air trapping is often incidentally diagnosed on

computed tomography A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

(CT) scanning. On expiratory films, retained hyperlucent gas will be visualised in cases of air trapping. Air trapping represents poorly aerated lung, but on its own is clinically benign. It is a common problem for smokers who dive. On diving the

lung volume Lung volumes and lung capacities are measures of the volume of air in the lungs at different phases of the respiratory cycle. The average total lung capacity of an adult human male is about 6 litres of air. Tidal breathing is normal, resting br ...

collapses and pushes air into the poorly aerated regions. On arising from a deep depth, these air-trapped areas of lung expand. This places great pressure on the lung tissue which can rupture.Johny A. Verschakelen; W. De Weber
"5.2.2 Air Trapping"
''Computed Tomography of the Lung: A Pattern Approach'', Springer, 2007, p. 51

References

{{DEFAULTSORT:Air Trapping Respiratory diseases