An 18-year-old male presented to the ED with complaints of right-sided chest pain. He reported that the night before coming to the ED, he was stretching and had acute onset of pain in the right side of his chest. He reported that the pain was worse with inspiration, and he was feeling mildly short of breath. He also reported that when he was walking around he felt light-headed.
Initial VS: HR 88, BP 130/75, RR 20, SpO2 100% on RA
Physical exam revealed a tall, thin male who appeared to be in pain, clenching the right side of his chest. There was mild tenderness over the right chest. Chest exam was notable for shallow respirations, and auscultation revealed breath sounds bilaterally.
Anyone could tell this man was going to have pneumothorax when he walked into the ED, and the providers taking care of him grabbed the ultrasound right away to make the diagnosis.
Here are the images of his left chest (unaffected side):
You can see normal sliding; meaning, there is no pneumothorax on the left. Sliding occurs when the two pleural interfaces in the chest slide against one another. This indicates that the lung is up and touching the chest wall.
Here is the right side:
Apex:
Mid-chest:
Base:
What do you notice?
There is NO sliding until the base of the lung! The diagnosis of pneumothorax was made within minutes of arriving to the ED. Here is a still pointing out the different structures that are seen if you are confused as to what you are looking at:
Now, the emergency providers just needed to prove there was a pneumothorax to other providers in the hospital so a chest x-ray was ordered. Here are the images:
Do you see a pneumothorax?
The radiologist read the CXR as normal. So what did the patient have?
There are some other conditions that can cause no sliding: adhesions, blebs, sub-cutaneous air, apnea, main-stem intubation.
Knowing this, the providers were still convinced that this man had a pneumothorax, so he was sent back for an expiratory chest film:
Do you see it?
There is a pneumothorax. The ultrasound was right!
Is ultrasound better than CXR at detecting a pneumothorax?
Short answer: YES
Multiple studies have shown that ultrasound has a better sensitivity in detecting pneumothorax than CXR, but has a slightly worse specificity (Sensitivity: 86-98% vs 28-75% and Specificity: 97-100% vs 100%). Of note, most of these studies were using ultrasound to detect pneumothorax in trauma, and the CXR was a supine AP film. This is an important distinction because it is difficult to see a small pneumothorax on a supine film because the air rises to the most dependent area of the lung, the anterior chest wall, not the apex as would be seen in an upright film. Therefore, there is often no sign of the pneumothorax on the CXR. The specificity of ultrasound in pneumothorax is not prefect because other conditions can cause no sliding in the absence of pneumothorax (adhesions, blebs, sub-cutaneous air, apnea, main-stem intubation).
The emergency providers estimated the size of the pneumothorax to be small to moderate. They elected not to drain the pneumothorax, but t0 treat conservatively with oxygen administration and observation. The patient did well in the hospital, and his CXR remained stable. He was discharged one day later in improved condition.
Bottom Line:
- Use ultrasound to rapidly detect pneumothorax with a better sensitivity than CXR.
- Know the other causes of absence of lung sliding on ultrasound (adhesions, blebs, sub-cutaneous air, apnea, main-stem intubation).
References
- Chen L, Zhang Z. Bedside ultrasonography for diagnosis of pneumothorax. Quant Imaging Med Surg. 2015;5(4):618-623.
- Reissig A, Copetti R, Kroegel C. Current role of emergency ultrasound of the chest. Crit Care Med. 2011;39(4):839-845.
- Wilkerson RG, Stone MB. Sensitivity of bedside ultrasound and supine anteroposterior chest radiographs for the identification of pneumothorax after blunt trauma. Acad Emerg Med. 2010;17(1):11-17.
