Deep Sulcus Sign - Pneumothorax

Pneumothorax simply refers to the presence of air in the pleural space. When this collection of air enlarges, it leads to the compression of mediastinal structures causing life-threatening tension pneumothorax. Pneumothoraces can be divided into three categories:

1. Primary spontaneous: no underlying lung disease (Connective tissue disorders)
2. Secondary spontaneous: underlying lung disease is present (COPD)
3. Iatrogenic/traumatic (trauma, biopsy, barotrauma)

Diagnosing Pneumothorax: 

• History and Physical Examination
• Bedside Lung USG
• CXR
• CT scan

USG - Check out this link to learn more about USG
M-mode can be used to determine movement of lung within the rib-interspace. Small pneumothoraces are best appreciated anteriorly in the supine position (gas rises) whereas large pneumothoraces are appreciated laterally in the mid-axillary line.


CXR in Pneumothorax 

A classical CXR shows: 

• Visible visceral pleural edge seen as a very thin, sharp white line
• No lung markings are seen peripheral to this line i.e. high Radiolucency 
• Peripheral space is radiolucent compared to adjacent lung 
• Completely collapse of lung
• Mediastinum shift is seen only in tension pneumothorax
• Subcutaneous Emphysema

On an erect chest radiograph, a pneumothorax will usually be apical. It can be challenging to visualise if it is small. Look carefully in the region above the line of the clavicle.

See pneumothorax demarcated on the second Chest X

 On your left, see the inspiratory film with PTx marked on the Right lung with yellow arrows. On your right, see the Expiratory film which shrinks the lungs and makes the Pneumothorax more obvious. Note the collapsed Right lung in this image. 

The Deep Sulcus Sign (CXR)

Pneumothorax can sometimes become a difficult diagnosis. Patients don't read textbooks and may not give you a classic presentation such as obvious hypoxia and absent breath sounds. 

When USG is available, start with a quick lung USG but it can be difficult to comment on breath sounds in a patient who is bleeding from nostrils and breathing at 40/min with broken ribs. USG with M-Mode still is your best bet here. CXR cannot be used to rule out a pneumothorax. Another issue is that ED patients are usually supine and a small pneumothorax float anteriorly in the supine position, and if it is not big enough to wrap around the lateral edge of the lung, it may be missed. So we need to be aware of subtle signs on a CXR. The deep sulcus sign is one of the more subtle signs. 

The deep sulcus sign is a dark lateral sulcus where the chest wall meets the diaphragm. The amount of lung in this area is less, so a small amount of air will tend to darken the area making it more prominent. 

If you see a deep sulcus sign on the CXR, strongly consider pneumothorax. If the patient is unstable, do needle decompression and insert with a chest tube. Aldo remember that a CXR always underestimates the true size of the pneumothorax. 

Patients with COPD may exhibit deepened lateral costophrenic angles due to hyperaeration of the lungs and cause a false deep sulcus sign.

CT scan - CT shows even the smallest of Pnemothoraces. 

I age from trauma.oh
Right tension pneumothorax - CT scan
The mediastinum is shifted to the left and the right lung compressed posteriorly

Take Home:

• PTx Diagnosis - Begin with History and Clinical exam followed by bedside USG - look for lung sliding (Lung sliding is Normal)
• Scrutinise the CXR and look for deep sulcus sign but beware of false deep sulcus in COPDs.
• CT only if high suspicion of Pneumothorax with equivocal USG and CXR 

Author:

              

     Lakshay Chanana

     

     Speciality Doctor

     Northwick Park Hospital

     Department of Emergency Medicine

     England

     @EMDidactic