This Image of the Week is courtesy of Paul Hausknecht, visiting medical student extraordinaire. It demonstrates the importance and utility of bedside ultrasound in pneumothorax detection.
On the left is the ultrasound image of the normal lung. You can clearly see lung sliding (sliding of the visceral pleura against the parietal pleura). This is often described as “ants marching on a log.” The video on the right shows the absence of lung sliding, which is concerning for a pneumothorax.
Paul then goes one step further and shows the “lung point” or “transition point.” This is the area where the normal inflated lung connects with the collapsed portion of the lung. You can see an area that is sliding transitioning into an area that is not. This finding increases the specificity of pneumothorax detection on ultrasound. However, lack of a lung point does not rule out a pneumothorax (if the entire lung is collapsed, there will be no transition point).
Pitfalls
Detection of a pneumothorax can get a little tricky when the heart gets in the way.
Here, you see movement in sync with the heartbeat. Cardiac movements are seen in areas where the heart touches the chest wall. Transmitted pulsations can also be seen through the consolidated lung. This finding is called a lung pulse. If you are concerned for a pneumothorax and see movement in time with the heartbeat, be careful not to call it normal sliding. Make sure to move your probe away from the heart and try to find an area of clear lung sliding (look for those ants marching on a log!).
Claire Abramoff