Quantifying Pneumothorax

In the unstable trauma patient, the absence of lung sliding is indication enough for chest tube placement due to pneumothorax. In the stable trauma or medical patient with absent lung sliding identification of the lung point confirms the presence of the pneumothorax and can help estimate its size. The lung point is the abrupt change from normal lung sliding to absence of lung sliding. It represents the edge of the pneumothorax (figure 6, video 6).

The lung point can be identified by rotating the probe to be in line with a rib space and following the pleural line laterally until the junction is identified.

A more posterolateral lung point corresponds to a larger pneumothorax. A lung point posterior to the mid-axillary line has an 82% sensitivity and 83% specificity for greater than 15% lung collapse on CT which is generally considered the recommended size for chest tube placement or drainage in a stable patient but again clinical judgement is warranted [7].

Note: The lung point may move subtly with respiration.

Figure 6: Lung point – CT illustration

Video 6: Lung point

Pitfalls – Cardiac Lung Point and Diaphragmatic Lung Point

There are two important mimics of the lung point, which should be recognized. The visceral and parietal pleura separate around the heart and at the edge of the diaphragm. These create a normal lung point at the left chest and inferiorly at the diaphragm (video 7&8). These are normal findings.

Care must be taken to not confuse the normal pleura at the heart or diaphragms as a lung point. In both cases, be sure to recognize the anatomy that the normal lung interfaces with. If normal lung touches pulsatile tissue in the left chest, it is likely the heart. If solid organ is visible consider that the diaphragmatic lung point and not a pathologic lung point is being identified.

Video 7: Cardiac lung point

Video 8: Diaphragmatic lung point