Anatomy & Physiology: Current Research
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One-lung Ventilation

A good understanding of airway anatomy and the tracheobronchial tree is essential to performing safe one-lung ventilation. The fiberoptic bronchoscopy enables a good visualization of the airway anatomy. The first branching point in the airway is the carina - which marks the bifurcation of the trachea into the two mainstem bronchi at the level of the sternal angle - left and right main bronchus. The trachea is about 10 to 13 cms long and has 12 concentric cartilaginous rings. These rings are deficient in their posterior aspect and thus for C-shaped rings as seen on a cross-section. The trachea divides in an area known as the carina which marks the division into left and right main bronchus.

The left main bronchus (LMB) continues for about 5 cms after which it branches into left lower lobe bronchus (LLLB) and left upper lobe bronchus (LULB). The right main bronchus (RMB) is shorter than the left side, but it is also wider and more vertical than the left side. The right main bronchus gives off the right upper lobe bronchus and then continues further as the bronchus intermedius. The take-off of the right upper lobe bronchus is about 2.0cm in adult men and about 1.6 cm in adult females. A knowledge of tracheal anatomy helps the anesthesiologist to position the double lumen tube for selectively isolating one lung for ventilation. This anatomy must undergo careful observation once the double lumen tube is in place and fiberoptic scope is inserted to check cuff position and verify correct tube placement.