Lung Point in M-mode

This week’s image of the week is brought to us by interns Deepa Patel, Dilani Weerasuriya, and soon to be new intern- Class of 2015, Lauren Hudak. They obtained an M-mode image of the "Lung Point", the only ultrasonographic finding that is highly specific for pneumothorax. 

As part of our E-FAST exam we typically look for lung sliding in the second intercostal space just lateral to the sternum. We use the presence of lung sliding to rule out pneumothorax.  This patient had no lung sliding on the right.

If we don't see sliding we can continue our evaluation by moving the probe evaluating each rib space down and out laterally (see image).   The “lung point” is the place on the chest wall where as the patient breathes and the lung expands, it will move in and out of view underneath your probe.  

Here they captured an M-mode image where we see this. At the beginning and end of the tracing we see “sand on the beach” the pattern of normal aerated lung. In the middle we see the “stratosphere” or “barcode sign” of a pneumothorax.

Remember that the lung point is a highly specific finding for pneumothorax, but has low sensitivity. If the lung is completely collapsed you will never find the lung point because the lung is too small and never comes into contact with the chest wall.