Lung hyperinflation

Lung hyperinflation is a common condition in patients with chronic obstructive pulmonary disease (COPD). It is also linked to ageing and other chronic diseases that cause airflow obstruction.

Pathology

The airflow limitation during expiration is produced by two factors:

  • destruction of the lung parenchyma

    • in healthy subjects, the volume reached by the lungs after exhalation is determined by the balance of forces between the inward elastic recoil pressure of the lung and the outward recoil pressure of the chest wall.

    • ageing or pulmonary parenchymal destruction from other causes emphysema) result in a displacement of this point of equilibrium to a higher volume.

  • airway defects

    • such as mucosal oedema, remodelling of airway mucus or impaction. In these cases, the expiratory airflow limitation is increased during exercise

The diseases that limit expiratory airflow produce lung hyperinflation. The most characteristic is chronic obstructive pulmonary disease (COPD).

Other diseases that cause an obstructive airflow pattern are

Radiographic features

Chest radiograph

Observable features include

  • flattened of diaphragmatic contours

    • considered one of the most sensitive indicators of hyperinflation and interobserver variability is small.

    • best seen in the lateral chest radiograph and consists of a loss of height of the convexity of the hemidiaphragm.

    • to measure, it is possible to draw a line connecting the sternophrenic angle and the posterior costophrenic angle.

      • this arch height should be greater than or equal to 2.5 cm.

      • it is considered clearly pathological when measures less than 1.5 cm.

    • minor measures correlate well with the functional importance of airflow obstruction. 

  • retrosternal space measurement

    • a horizontal line is drawn from a point allocated 3 cm below the junction between the manubrium and sternal body, on the posterior cortex of the sternum, and the ascending aorta point. In cases of increased retrosternal space, this distance is equal or greater than 2.5 cm.

  • air trapping: when comparing two radiographs acquired in maximal inspiration and maximal expiration, the vertical movement of the diaphragm is less than 3 cm.

  • ribs appearances:

    • more than 6 above or 10 posterior ribs in the mid-clavicular line at the lung and diaphragm level

    • horizontalization of ribs.

  • presence of air below the heart.

  • increased anteroposterior diameter of the chest, also called barrel chest.

  • hyperlucent lungs (less bronchovascular markings per cm2)


CT

Observable features include

  • air trapping: best seen in expiration.

  • measuring the length of the anterior union line

    • this is a masurement of retrosternal space more reproducible than in the chest radiograph.

  • Saber sheath trachea

    • a pathognomonic finding of chronic obstructive pulmonary disease (COPD).

    • it refers to decrease in the diameter of the trachea in the coronal plane and increase in the sagittal plane. It can be also seen on the chest radiograph comparing the posteroanterior and lateral projections.

  • vascular changes

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Article information

rID: 50343
System: Chest
Synonyms or Alternate Spellings:
  • Pulmonary hyperinflation
  • Hyperinflated lungs
  • Hyperinflation of lungs

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Cases and figures

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    Figure 1: measurements of hyperinflation
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    Case 1: marked hyperinflation
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    Retrostenal airsp...
    Figure 2: measurements of hyperinflation
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    Marked hyperinfla...
    Case 2 : marked hyperinflation
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