Lung hyperinflation is a common feature of patients with chronic obstructive pulmonary disease (COPD). It is also linked to ageing and other chronic diseases that cause airflow obstruction.
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 (e.g. emphysema) results in a displacement of this point of equilibrium to a higher volume.
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
- cystic fibrosis
- some interstitial diseases such as
Observable features include
flattened hemidiaphragmatic contours
considered one of the most sensitive indicators of hyperinflation and interobserver variability is small.
best seen on 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.
more than 6 anterior or 10 posterior ribs above the diaphragm level on the midclavicular line
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 unit area)
Observable features include
air trapping: best seen in expiration.
measuring the length of the anterior junctional line
this is a measurement of the retrosternal space more reproducible than in the chest radiograph.
a pathognomonic finding of chronic obstructive pulmonary disease (COPD).
it refers to a 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.
an indirect sign of destruction of the lung parenchyma.
emphysema causes destruction of the lung parenchyma and pulmonary arterial hypertension.
- 1. O’Donnell DE, Webb KA, Neder JA. Lung hyperinflation in COPD: applying physiology to clinical practice. COPD Research and Practice. 2015;1:4.
- 2. Thomas M, Decramer M, O'Donnell DE. No room to breathe: the importance of lung hyperinflation in COPD. Primary care respiratory journal : journal of the General Practice Airways Group. 22 (1): 101-11. doi:10.4104/pcrj.2013.00025 - Pubmed
- 3. O'Donnell DE, Laveneziana P. The clinical importance of dynamic lung hyperinflation in COPD. COPD. 3 (4): 219-32. Pubmed