US Probe: Ultrasound for Lung Point

Robert J. Strony DO, RDMS, RVT (@Stronysono – Program Director of Geisinger Emergency Medicine, Geisinger Health System POCUS Director) // Edited by Stephen Alerhand MD (@SAlerhand – EM Resident Physician and Incoming Ultrasound Fellow, Icahn School of Medicine at Mount Sinai) and Manpreet Singh (@MPrizzleER – Assistant Professor in Emergency Medicine / Department of Emergency Medicine – Harbor-UCLA Medical Center)

Clinical Scenario

A 30 year-old male presented with right-sided chest pain s/p motorcycle collision. Upon arrival, the patient was noted to have mild tachypnea with an oxygen saturation of 92%. A trauma alert was initiated, a supine portable chest x-ray was negative for acute pathology, and an e-FAST was quickly performed with the video clips below obtained.

Video 1 reveals a lung point sign within a single intercostal space utilizing a low-frequency curved transducer in B mode. Note that the adjacent space shows normal lung sliding.
Video 2 depicts normal lung sliding in an intercostal space and absent lung sliding in the adjacent space, also in B mode.
Video 3 depicts a high-frequency transducer image of absent lung sliding, again in B mode. The classic “sandy beach” appearance will alternate with the “bar code sign.”
Video 4 confirms the pneumothorax on CT scan.

Take Home Points

• The presence of lung sliding on bedside ultrasound is superior to chest x-ray for detecting pneumothorax in the trauma patient.1
• In addition to lung sliding, we should always search for the lung point. This is the point where normal pleural interface interacts with the pneumothorax boundary—where the visceral pleura (lung) begins to separate from the parietal pleura (chest wall) (Image 1). The lung point is 100% specific for detecting pneumothorax on bedside ultrasound.2

• The lung point is caused by sliding lung intermittently contacting the chest wall during inspiration and can be used to determine the actual size of the pneumothorax.3 Limitations to this measurement include respiratory variation and only having visualization of the anterior projection of the pneumothorax. False mimics include the following interfaces: The left chest with the heart and the inferior lung with the diaphragm.
• The lung point sensitivity is low and may not be seen in large pneumothoraces with complete retraction of the lung, where global lung sliding is absent.4

References

1. Blaivas M., Lyon M., and Duggal S.: A prospective comparison of supine chest radiography and bedside ultrasound for the diagnosis of traumatic pneumothorax. Acad Emerg Med 2005; 12: pp. 844-849.
2. Lichtenstein D., et al: The “lung point”: an ultrasound sign specific to pneumothorax. Intensive Care Med 2000; 26: pp. 1434-1440.
3. Husain, Lubna F et al: Sonographic diagnosis of pneumothorax. Journal of Emergencies, Trauma, and Shock 2012; 5(1): pp 76-81.
4. Volpicelli, G.: Sonographic diagnosis of pneumothorax. Intensive Care Med 2011; 37: pp. 224-232.