figure 1-6 Cross-sectional computed tomography views of tracheal anatomic relationships in the mediastinum. Diagram shows level of sections A at T3-4, and B at T4-5. A, Thoracic trachea. B, Supracarinal trachea. Mediastinal structures are labelled.

figure 1-7 Many variations occur in the arrangement of the branches arising from the aortic arch. The two most common patterns are (A) with separate origins of brachiocephalic and left carotid arteries, and (B) with a common origin. In both, a separate left vertebral artery may arise from the arch distal to the left carotid (C,D) and confuse the tracheal surgeon. The common origin may complicate resection of tracheal lesions that are adherent to the trunk or the treatment of tracheoarte-rial fistula. Adapted from Williams GD and Edmonds HW.14

superior vena cava on the right, the aortic arch on the left, the pulmonary artery inferiorly, and the bra-chiocephalic vessels superiorly (see Figure 23-7 in Chapter 23, "Surgical Approaches"). The presence of major vascular structures in close proximity to the trachea makes exposure of its full extent difficult through any single incision. These anatomic facts must be considered in planning surgical approach to a tracheal lesion (see Chapter 23 "Surgical Approaches").

The previously undisturbed pretracheal plane, except for the point of attachment of the thyroid isthmus, may be easily developed bluntly because it consists of areolar tissue with few blood vessels. Normally, it is essentially avascular except for the rare thyroidea ima artery or an even rarer small posterior branch from the brachiocephalic artery to the trachea. A few inferior thyroid veins overlie the upper trachea immediately below the thyroid isthmus. These drain into the left brachiocephalic vein most commonly. The attachments of connective tissue to the trachea are loose enough so that vertical movement is easily possible to a considerable degree both functionally and surgically. The trachea is, however, fixed by the sling of the aortic arch over the left main bronchus where relatively little sliding motion occurs. With the increasing anteroposterior diameter of the thorax with age, related to vertebral kyphosis, this point of fixation draws the carina further posteriorly and the trachea falls into a more horizontal position when viewed laterally (see Figure 1-4B). Mobility of the trachea with cervical extension becomes limited, as previously noted.

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