The deviation of the trachea when palpated in the neck area.
The trachea can be shifted from its mid-line position in neck by factors that either push it to the opposite side of factors that pull it to the same side. Usually these influences are based in the mediastinal and lung areas. Pneumothorax which results in increased pressure on the affected side will push the trachea to the opposite side (contralateral), so will pleural effusion and large tumous. The trachea can also be pulled towards the side which is affected (ipsilaterally) by conditions such as fibrosis, atelectasis, pneumonectomy,
Explained to the patient that you are going to feel their neck. With your thumb and index finger gently feel the descending course of the trachea until you reach the chest bone (manubrium/sternum). Then with your index finger resting above the suprasternal notch feel the trachea (and its rings) as it descends into the chest cavity and again ascertain if this is central in relation to the suprasternal notch.
(Full details and demonstration of procedures are provided with the DVD/videos and associated study material)