Ultrasound Quiz 2: Spooky Lungs

Question 1:

During your ER rotation, your resident is worried about a patient who was stabbed multiple times in the chest. He shows you this ultrasound image, and asks for your opinion. What should you tell him?

Explain that you see normal lung sliding but that you cannot rule out a pneumothorax or hemothorax based on this image. Tell him to prepare a chest tube because you see a double lung point. The presence of A lines indicate pneumonia. This is the pelvis, you can see the pubic symphysis. He should scan the lungs. There is free fluid, so it is a hemothorax.

Yes great job! In this image we see normal lung sliding in an intercostal space. However, in order to rule out a pneumothorax in a lung, you need to be able to identify either lung sliding, comet tails or a lung pulse in 3 different intercostal spaces. Remember to also scan the 2nd lung as well!
Since we only see 1 intercostal space, we can't rule out a pneumothorax.

Although we see normal lung sliding here, we cannot rule out a pneumothorax just yet!

First things first - orient yourself! In this scan, we see the following:
- Ribs! Because bone is so dense, sound waves do not travel through them. The result is a hyperechoic (white) structure, with a shadow in the far field (below it on the screen) where the tissue cannot be imaged. In this image, we see 2 ribs and their corresponding shadows - one on screen left, and one on screen right. The space between the ribs is called the intercostal space.
- Pleural line! It is a hyperechoic (white) line in the intercostal space. It represents the 2 layers of lung pleura.

Lung sliding and pneumothorax:
In this image, we see lung sliding, which is normal. It occurs when the visceral and parietal pleura of the lungs slide over each other as the lungs expand and contract which causes the pleural line to shimmer.
In a pneumothorax or hemothorax, the layers of the pleura become separated as the potential space that separates them fills up with air or blood, respectively. As the layers no longer slide against one another, lung sliding is interrupted.

Ruling out pneumothorax:
If you are able to identify either lung sliding, comet tails or a lung pulse in 3 different intercostal spaces, then you can rule out pneumothorax in that lung.
In this image, we only see 1 intercostal space with lung sliding, so we cannot rule out pneumothorax just yet, we would have to image the other intercostal spaces. Don't forget to check the 2nd lung as well!

Extra definitions (taken from the CPOCUS website):
- Comet tails = short white line arising from the pleura caused by reverberation of the ultrasound beam between the visceral and parietal pleura
- Lung pulse = Cardiac pulsation transmitted to the pleural line in a poorly aerated lung (i.e., atelectasis or main stem intubation)

Question 2:

In March of 2020, a patient presented to the ER with a 2 day history of worsening dyspnea, with an O2 sat of 42%. With the help of the ultrasound provided, you most suspect:

Who knew US could be used to diagnose COVID-19?

This scan is indicative of COVID-19 pneumonitis. As explained by Dr. Cian McDermott, an emergency physician in Ireland: "coarse and irregular pleura, patchy B-lines, and small areas of consolidation" should alert you to this diagnosis (thepocusatlas.com)

Question 3:

A 56 year old female presents with fever, chills and dyspnea. The following US is performed. What do you see?

Great job! The positive spine sign and negative curtain sign point to a pleural effusion!

First things first - orient yourself! In this image we see the following:
- The liver on screen right with its "starry nigh" appearance.
- The diaphragm on screen left, which looks like a curved, hyperechoic (white) line. We can see the diaphragm expanding and contracting slightly when the patient breathes. (NB: In order to complete a determinate scan, the diaphragm must be visualized between the 6 o'clock and 9 o'clock positions.)
- The posterior costophrenic angle, where the lung pleura along the posterior rib cage intersects with the posterior aspect of the diaphragm. Usually, fluid would collect here due to gravity if there is any.
- The spine, in the far field (inferior aspect of this image), which looks like a hyperechoic (white) squiggly line.

This patient has a pleural effusion, here are a couple clues that help us make the diagnosis:
1 - Negative curtain sign. The curtain sign is a phenomena observed on ultrasound in the absence of a pleural effusion. It is caused by the lungs expanding, pushing the liver caudally (towards the feet) and the aerated tissue will scatter the ultrasound waves, distorting the image. In this case, there is fluid in the posterior costophrenic angle preventing the aerated tissue from entering the field on inspiration. Remember, fluid appears anechoic (black) on ultrasound!

2- Positive spine sign. In the absence of a pleural effusion, the spine is only visible caudad to the diaphragm (on screen right). Normally, the aerated lung tissue cephalad to the diaphragm (screen left) scatters the ultrasound waves and distorts the image, preventing us from obtaining a clear image of the spine above the level of the diaphragm. Here, however we can see the spine cephalad to the diaphragm (screen left)! This is because sound travels very well through fluid, allowing it to act as an acoustic window. The ultrasound waves travel easily from the probe to the spine when someone has a pleural effusion.

(Extra tip: If you see the diaphragm from 6 o' clock until 12 o' clock instead of 9 o' clock, you could consider a pleural effusion, since normally we shouldn't be able to see the diaphragm all the way up. It isn't very clear in this scan however)