Lessons from lung ultrasound

We read with interest the case report titled ‘Pitfalls in the ultrasonographic diagnosis of pneumothorax’. ¹ This describes a complex case in which the use of lung ultrasound did not diagnose a pneumothorax later visualised by computed tomography (CT). Quite rightly, the authors emphasise that clinicians who use lung ultrasound should have a firm understanding of its possible pitfalls, as one would for any other diagnostic technique. They highlight a number of reasons why lung ultrasound may ‘fail’ to diagnose a pneumothorax, the most pertinent of which being the use of a ‘standard’ examination sequence. We believe there is further learning that could be had from this case, specifically around (1) scan indication and method and (2) governance.

The case has red flags that would render a standard ultrasound examination of the thorax very difficult: a sub-pectoral breast prosthesis would block ultrasound to most of the anterior chest and thoracic surgery with chest drains would raise the likelihood of adhesions or loculated pathology. We presume that the modified Bedside Lung Ultrasound in Emergency protocol ² was used, although this is not explicitly stated. This protocol was originally described to diagnose the responsible pathology in the acutely dyspnoeic patient. In our opinion, it is not valid in such complex cases because patients with multiple pathologies were excluded from its analysis. Scanning for a pneumothorax in the intensive care unit (ICU) can require a far more thorough examination technique and a sonographer might have to hunt for a ‘lung point’ to positively confirm a pneumothorax. For example, small apical pneumothoraces in trauma series are missed during extended Focused Assessment with Sonography for Trauma trauma ultrasounds, ³ as demonstrated in this case. (Figure 3 showing a small loculated apical pneumothorax). The authors do not explicitly describe the results of the lung ultrasound scan and there are no images to assess the ultrasound findings. However, based on the transverse CT sections, ‘lack of lung sliding’ should occur lateral to the breast prosthesis. An experienced operator performed the test, but there is no indication of the probe used, which signs were found or how the images were stored and reviewed. These last observations lead onto our second point.

The education and governance of bedside critical care ultrasound in many hospitals are an unknown quantity. The Royal College of Radiology have produced standards for delivery of an ultrasound service ⁴ which clearly states that ultrasound governance should be included in the department’s overall governance structure and that all users should have the appropriate accreditation and ongoing training. This is echoed in guidance from the AAGBI/RCOA/ICS joint document on ultrasound. ⁵ Point-of-care ultrasound is performed in different areas of the hospital, and there are now a number of competency training packages supported by governing organisations in the UK, e.g. Core UltraSound in Intensive Care by the Intensive Care Society. Accredited individuals must maintain Continuous Professional Development, regularly audit their scans and undergo multidisciplinary review of their cases with more experienced individuals. ⁶ This case is clearly one that would benefit from such detailed review and in doing so would give a significant degree of learning to all point-of-care practitioners. We commend the authors in publishing their case report with the hope that understanding and practice will be improved.