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Segmental and sub-segmental divisions

A thorough knowledge of segmental lung anatomy is fundamental, and should be mastered by all bronchoscopists. For training purposes, glass replicas of the bronchial tree are used. In general this model is positioned, as it would be in a patient lying supine. In our service we recommend that trainees also accustom themselves to viewing the model not only in the supine position but also in the anterior and lateral decubitus positions.

supine, anterior and lateral decubitus positions

As we shall see later in this website, placing the patient in the lateral decubitus position can be essential to safety since it is the only way to prevent flooding of both lungs in case of massive bleeding.

We have positioned all of our patients undergoing fiberoptic bronchoscopy in the lateral decubitus position with the diseased lung down for the past 20 years. We believe this positioning has three fundamental advantages : the absence of secretions at the level of the pharynx, minimizing discomfort both to the patient and the physician, and improved safety insofar as it precludes flooding of the contralateral lung in case of massive bleeding or during large volume broncho-alveolar lavage. Learning to orient oneself in this position can be challenging. However, tilting the patient’s head at the beginning of the procedure can help the endoscopist to identify key landmarks.

Orientation is simple in the case of the rigid bronchoscope. With the patient lying flat on his back, right is right, posterior bronchi are inferior etc. During fiberoptic bronchoscopy, and especially when using the video-endoscope orientation is relative to those bronchi already identified.

For example, the middle lobe is always opposite from the superior segment of the lower lobe,

and the anterobasal segmental bronchus is always parallel to the lingula.

(in red) Similarly, the anterior segment of the left upper lobe, the lingula, and the anterobasal segment, follow an anterior trajectory in parallel.

(in blue) The posterior segment of the left upper lobe, the superior segment of the lower lobe and the posterobasal segmental bronchi follow an posterior trajectory.

(in red) On the right, the anterior bronchi are in front, including the anterior segment of the right upper lobe, middle lobe, and anterobasal segmental bronchus of the lower lobe.

(in blue) The posterior bronchi are behind, including the posterior segment of the upper lobe, apical segment of the inferior lobe, and posterobasal segmental bronchus.

Normally the right lung has three lobes (upper, middle and lower) and the left has two lobes (upper and lower). Each lobar or secondary bronchus divides into two to five tertiary or segmental bronchi.

Normally there are ten bronchopulmonary segments in the right lung and eight in the left. Great variation is found in the more peripheral branching.

The international nomenclature used for the bronchi today is well established. It is based on the early systems of Jackson-Huber or Boyden and extends to sub-subsegmental bronchi. In this system the traditional names are used for the large bronchi, i.e., the main stem and lobar bronchi (first order of branching). The peripheral bronchi are numbered indicating the originating subsegmental branch followed by a letter.

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