Question 23

College comments

Syllabus topic/section: 2.1.5.a Respiratory Intensive Care L2 topic: Chest Ultrasound

Discussion: 

The question assessed candidates’ understanding of the application of lung ultrasound in a hypoxic patient post-intubation, as well as its general advantages and disadvantages. A standard response was expected to include potential causes - such as pneumothorax, collapse or consolidation - and describe their characteristic appearance on lung ultrasound.

While most candidates demonstrated some familiarity with lung ultrasound terminology, most responses revealed significant knowledge gaps, particularly in differentiating between causes. Higher scoring answers used standard ultrasound descriptors and clearly explained how to identify specific pathologies. For example, diagnosing pneumothorax was described with use of appropriate ultrasound findings like absent lung sliding and presence of lung point.

Some candidates confused ultrasound B-lines with radiographic Kerley B-lines, and M-mode findings were often misinterpreted in the context of pneumothorax. Complex effusions were incorrectly described to represent empyema by some candidates.

It is important to note that the question focused specifically on lung ultrasound; therefore, references to focused echocardiography were not credited. Additionally, in Part b), some candidates repeated the same points as both advantages and disadvantages (e.g., “cheap” vs “expensive”, “portable” vs “difficult to move” machines) which waste time and space which could have been given to more discriminating facts.
 

Interpretation

a) 

The lung ultrasound findings that could explain this patient's hypoxia include:

• Pneumothorax - missing the pleural sliding; M-mode "seashore sign"
• Pulmonary oedema is characterised by multiple (>3) B-lines in multiple intercostal spaces
• Consolidation is characterised by "hepatisation" and dynamic air bronchograms
• Atelectasis can be distinguished from consolidation by the presence of static air bronchograms
• Pleural effusion is identified by the presence of hypoechoic fluid and by the "jellyfish sign", which describes the floopy movement of the collapsed lung in the pleural fluid.

b)

Advantages:

• Instant bedside availability
• Low cost (beyond the initial outlay for the unit)
• No exposure to ionising radiation
• No requirements to transport the patient anywhere (although one must admit that all ultrasound does not have to be POCUS)
• For some conditions, eg. pneumothorax, it may be more sensitive: for example, theoretically even a 1mm sliver of pneumothorax can be detected by POCUS, and it can capture effusions in the posterior pleural space that is usually invisible on CXR

Disadvantages

• Training and experience is required for accurate interpretation
• Expertise of the operator is directly related to the quality of the images
• Some necessary windows may be missing due to chest wall deformities, wounds or dressings
• Not all of the lung volume is accessible even under the best conditions
• Takes longer than a single chest Xray
• Large amounts of adipose tissue interfere with ultrasound transmission
• Misunderstood findings or incorrectly acquired images may result in incorrect management
• For many conditions, CT or Xray radiology remains the gold standard