Endobronchial ultrasound (EBUS)

EBUS is a new bronchoscopic technique which involves the use of a specialised bronchoscope for performing airway procedures. To understand the use of this new instrument one first has to understand the anatomy of the mediastinum which is relevant.

Mediastinum is the space in the chest between the two lungs. The wind pipe, or trachea, normally divides into two smaller wind pipes, or main bronchi, for the purpose of supplying each individual lung. The trachea and the major bronchi lie in the space between the two lungs, i.e. the mediastinum. In addition to the airways, the mediastinum also contains other structures such as lymph nodes, blood vessels, nerves and most importantly, the heart. Lymph nodes are soft tissue structures located adjacent to the airways. They are commonly involved in many respiratory disorders such as tuberculosis, sarcoidosis, lung cancer, lymphoma and some other rare conditions.

The mediastinum is an enclosed space, much like a landlocked country. Though radiological investigations such as computed tomographic (CT) scans provide detail about the anatomy, access to the mediastinum is limited. Such an access is essential to obtain biopsy materials for histo/cytological examinations for diagnosis. Using a bronchoscope, one can obtain samples from certain mediastinal structures such as lymph nodes. However, locating the lymph nodes from inside the airways is difficult. It is in this situation that the EBUS scope comes into its use.

The essential difference between the conventional and the EBUS scope is the presence of an ultrasound transducer at the tip. With this, the mediastinal anatomy can be imaged from within the airways. Lymph nodes can be located based on the ultrasonic image and sampled under ultrasonic vision. This has manifold benefits:

i. Lymph nodes can be easily and accurately located

ii. Blood vessels and other mediastinal structures can be avoided

iii. Blood vessels within the lymph nodes can also be avoided.

 Therefore, the success rather are better and complications fewer with EBUS guided procedures.