helpsimple searchclear selectionselect all
Dictionary assisted search
All words
Any word/input
Exact phrase
in these
lexical topics:
  • Physics, Techniques and Procedures
  • Normal Anatomy
  • Musculoskeletal Imaging
  • Breast Imaging
  • Gastrointestinal Imaging
  • Urogenital Imaging
  • Chest Imaging
  • Cardiovascular Imaging
  • Neuroradiology
  • Head and Neck Imaging
  • Paediatric Imaging
 
 
 
Chest Imaging

Overinflation

(also called hyperinflation), increased expansion of the lungs with air. Overinflation of the lungs must be considered at full inspiration and be distinguished from air trapping on expiration. Overinflation or hyperinflation may be diffuse or localized. A general excess of air in the lungs may be observed in obstructive pulmonary disease such as emphysema, asthma and constrictive bronchiolitis, and in cystic lung disease such as pulmonary histiocytosis X and lymphangiomyomatosis. Radiographic features include changes in the diaphragm, the retrosternal space and the retrocardiovascular silhouette. The normal domed configuration of the diaphragm is flattened (Fig.1). The severity of flattening may be so marked in emphysema as to render the diaphragmatic contour concave rather than convex. The low position of the diaphragm increases the angle of the costophrenic sinuses, sometimes almost to a right angle. Costophrenic muscle slips, extending from the diaphragm to the posterior and posterolateral ribs, may be prominent. The depth of the retrosternal space is increased on the lateral film. When the diaphragm is depressed the heart tends to be elongated, narrow and central in position.

Overinflation of a segment of one or more lobes, the remainder of the lung being normal, may occur with or without air trapping. Overinflation with air trapping results from obstruction of the exit of air by affected lung parenchyma (lobar emphysema in infants and bronchial atresia) (Fig.2). Overinflation without air trapping is a compensatory process: part of the lung takes a larger volume than normal in response to loss of volume elsewhere in the thorax. This may occur after surgical resection of lung tissue, or as a result of atelectasis or parenchymal scarring. The radiological signs of localized overinflation include alteration in lung density, volume and vascular pattern. Increased translucency of the overinflated areas is associated with an increased volume, recognized by the displacement of contiguous structures (Fig.2). In a lower lobe, hemidiaphragm may be depressed and the mediastinum shifted to the contralateral side. In an upper lobe, the mediastinum may be displaced and the thoracic cage extended. If a whole lung is involved, the hemithorax is enlarged, the diaphragm is depressed, the mediastinum shifted and the thoracic cage enlarged. Outward bulging of the fissure is also a reliable sign of lobar overinflation. Alteration in vascular pattern consists in a splaying out of the vascular opacities throughout the affected lungs in a distribution consistent with the extent of overinflation.

PG

To view high resolution images,
please register first.

Click  here to register.

Already registered? Enter your e-mail in the window below.
Re-register

Fig.1

PA chest radiograph of a patient with severe obstructive pulmonary disease related to constrictive bronchiolitis and bronchiectasis. Diffuse overinflation is marked with a low position of the diaphragm and flattening of the dome.
Overinflation, Fig.1
Overinflation, Fig.2 (a)
Overinflation, Fig.2 (b)