Key points
Show Chest X-rays are conventionally acquired in the inspiratory phase of the respiratory cycle. The radiographer asks the patient to, 'breathe in and hold your breath!' Patients who are short of breath, or those who are unable to follow the instructions may find this difficult. When interpreting a chest X-ray it is important to recognise if there has been incomplete inspiration. If the image is acquired in the expiratory phase, the lungs are relatively airless and their density is increased. Also, the raised position of the diaphragm leads to exaggeration of heart size, and obscuration of the lung bases. Assessing inspirationTo assess the degree of inspiration it is conventional to count ribs down to the diaphragm. The diaphragm should be intersected by the 5th to 7th anterior ribs in the mid-clavicular line. Less is a sign of incomplete inspiration. ExpirationHover on/off image to show/hide findings Tap on/off image to show/hide findings Click image to align with top of page Expiration
InspirationHover on/off image to show/hide findings Tap on/off image to show/hide findings Click image to align with top of page Inspiration
While checking for adequate inspiration you may notice that a patient's lungs are hyperexpanded (>7th anterior rib intersecting the diaphragm at the mid-clavicular line). This is a sign of obstructive airways disease. It is possible to assess for hyperexpansion by counting ribs, or by checking for flattening
of the hemidiaphragms. Normal expansionHover on/off image to show/hide findings Tap on/off image to show/hide findings Click image to align with top of page Normal expansion
HyperexpansionHover on/off image to show/hide findings Tap on/off image to show/hide findings Click image to align with top of page Hyperexpansion
How many posterior ribs should be visualized on a PA chest?Full inspiration is usually not achievable in ill patients; generally, only eight or nine ribs are visualized above the diaphragm. Three posterior ribs should be seen above clavicles if the CR angle is correct. Clavicles are projected higher and the ribs assume a more horizontal position.
How many posterior ribs should be visible?Ideally 7-9 ribs should be visible. Less than 7 suggests poor effort by the patient and/or low lung volumes as in restrictive lung disease, atelectasis, etc. 10 or more ribs typically suggests hyperinflation as in COPD, asthma, bronchiectasis.
How many posterior ribs are shown above the diaphragm?Normally, six anterior ribs and nine posterior ribs should be seen above the diaphragm.
How many ribs should be visible above the diaphragm?Full inspiration inflates the lungs and moves the diaphragm down, allowing the maximum visualization of ribs above the diaphragm, usually 9 or 10 upper ribs. Full expiration elevates the diaphragm, allowing for visualization of more ribs below the diaphragm, usually ribs 8 - 12.
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