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Visualization of the airways for diagnosis or treatment can involve the use of either flexible or rigid bronchoscopes. Flexible bronchoscopes generally are used for evaluation and biopsy, whereas rigid bronchoscopes are uniquely capable of establishing and maintaining airway control in a life-threatening situation such as acute upper airway obstruction or massive hemoptysis. Although these procedures often can be used interchangeably, the rigid bronchoscope is uniquely suitable for applications that require precise airway measurement (e.g., tracheal stricture) or a large working port (e.g., endobronchial tumor).

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The trachea extends from the cricoid cartilage of C6 to the origin of the left and right main stem bronchi at the carina (T6). In normal adults, the trachea is 12 cm long (range 9–15 cm). The normal trachea is approximately 16 mm in lateral diameter and 14 mm in anteroposterior diameter. The anterior wall of the trachea is composed of cartilaginous horseshoe-shaped rings, and the posterior wall is a continuous membranous wall (Fig. 52-1).

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Figure 52-1.
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Anatomy of the hypopharynx, larynx, and trachea.

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The left mainstem bronchus, approximately 4.5 cm in length, is oriented at 45 degrees to the axis of the trachea. The right mainstem bronchus is much shorter (1.5 cm) and is oriented more vertically (25 degrees). The right mainstem bronchus gives rise to the right upper lobe bronchus at the level of the carina. The right upper lobe has three segments corresponding to the apical (B1), posterior (B2), and anterior (B3) segments. The airway distal to the right upper lobe orifice is the bronchus intermedius. The bronchus intermedius extends 2 cm from the right upper lobe to the right middle lobe bronchus. The middle lobe bronchus is 1.2–1.5 cm in length and has a diameter of 8 mm. The middle lobe has a medial (B4) and lateral (B5) segment. The superior segment (B6) of the lower lobe arises at the level of the middle lobe bronchus. The orientation of the basilar segment orifices (B7–10) is variable, and these generally are considered collectively (i.e., composite basilar segmentectomy).

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The origin of the left upper lobe bronchus is lower than that of the right upper lobe bronchus. The left upper lobe orifice branches into upper and lower divisions. The upper division is approximately 1 cm long and gives rise to three segments, two of which are often combined (e.g., B1 + B2 and B3). The lower division is composed of the superior (B4) and inferior (B5) divisions of the lingula. The lower lobe superior segment (B6) has a similar course to the right side. There are only three basilar segments (B8–10; the B7 segment is absent) in the left lower lobe compared with five in the right lower lobe. Similar to the right side, the basilar segments are vertical in orientation and generally considered as a composite structure.

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