THE LOCATION of the tracheal bifurcation to the right of the midline is a consequence of the asymmetrical structure of the respiratory organs.1 In this position there is a static-dynamic balance in the cavity of the thorax. The tissue tension in the pulmonary parenchyma, the resistance to the current of air in the bronchial system, and the bilateral pleural pressure are balanced in such a manner that no horizontal or sideward shift of the carina takes place during inspiration and expiration.
If one of the three factors mentioned, tissue tension, pleural pressure, or bronchial resistance to the current of air, undergoes a change, this necessarily leads to a disturbance of the functional balance, particularly when this change involves one side only. Owing to this, the carina, insofar as it is able to move freely, shifts in a horizontal direction to the right or to the left on inspiration, to