A tracheal bronchus is defined as “displaced” when the normal right upper lobe bronchus (or ≥1 of its segments) is transposed from the right mainstem bronchus to the trachea. The corresponding bronchus or segment is missing from its normal position. Displacement of the entire right upper lobe bronchus is called a “pig bronchus” or “bronchus suis,” because this is the normal morphology in swine, as well as giraffes, cattle, camels, goats, and sheep.6 The most common configuration is a displaced right apical segment.7 Our patient had displaced apical and posterior segments of the right upper lobe, whereas the anterior segment emerged from the standard location, off the right mainstem bronchus. Vascular supply and drainage of displaced bronchi are typically normal.1,4
Supernumerary bronchi are extra segments or bronchi. In these cases, the right upper lobe is of normal morphology (trifurcated) and location, off the right mainstem bronchus, but an additional bronchus emerges from the trachea. These bronchi may have epiarterial blood supply that could complicate surgical resection.4,8
The pathogenesis of tracheobronchial abnormalities is established within the first 16 weeks of embryogenesis, when the major tracheobronchial tree is formed.1,9 The exact etiology is unknown, but there are 3 competing theories to the development of tracheal bronchi: (1) the failure of regression of tracheal buds in utero,1,8,9 (2) “migration” of bronchi to new sites during tracheobronchial lengthening,1,5 and (3) disruption of normal embryogenesis,1,8,9 a hypothesis supported by the increased incidence of other congenital abnormalities in patients with tracheal bronchi.8,10 Associated congenital anomalies include trisomy 21, congenital heart disease, laryngomalacia, laryngeal webs, tracheal stenosis, rib and vertebral abnormalities, and anomalous pulmonary vascular supply and drainage.9
The presence of a tracheal bronchus in the adult is typically of minimal concern,4 although there have been rare case reports of pulmonary malignancies deriving from the lung tissue supplied by the tracheal bronchus.6 In the pediatric population, there is an increased risk of respiratory complications, including chronic atelectasis, recurrent infection, bronchiectasis, and cysts.4,8 For situations that require airway management, lung isolation, and/or pulmonary resection, a tracheal bronchus is important in both adult and pediatric patients. In the event the tracheal bronchus orifice is occluded or intubated with a SLT, complications such as atelectasis, hypoxemia, and barotrauma may ensue.4,5,10 Furthermore, lung isolation can prove to be challenging or inadequate, as in the case discussed herein.3,7,11–14
Our patient had a displaced type II tracheal bronchus along with a left-shifted carina and apically retracted left mainstem bronchus. In our patient, a left DLT could not be placed and a right-sided DLT would not have been appropriate given the anatomy and nature of the surgery. Inappropriate positioning of a left DLT has been described in the setting of a tracheal bronchus, causing bilateral upper lobe obstruction as the tracheal cuff occluded the tracheal bronchus and the bronchial cuff occluded the left upper lobe.11 In our case, we were unable to place the DLT in the left mainstem bronchus because of the left-shifted carina. A smaller DLT could have been attempted; however, because of the angle of the left mainstem bronchus, similar positioning difficulties may have occurred. Even if a small left DLT could have negotiated the left-shifted carina, the orifice of the bronchial lumen may have been occluded by the bronchial wall of the apically retracted left mainstem bronchus DLTs with a flexible wire-reinforced bronchial lumen (Phycon; Fuji Systems Corp., Tokyo, Japan), were designed to circumvent this issue exit but were not available to us. Instead, our solution was to use separate bronchial blockers for the tracheal bronchus and right mainstem bronchus.
Other described solutions for right lung isolation in cases with tracheal bronchi, in which a left DLT was not, or could not be used, include (1) the use of a Univent (Fuji Systems Corp., Bunkyo-Ku, Japan) endotracheal tube in combination with a Fogarty catheter,7 (2) the use of a single bronchial blocker positioned in the right mainstem, with the cuff high enough to block a carinal tracheal bronchus as well as the right mainstem,14 and (3) the use of a SLT and blocker, in which the cuff of the SLT occludes the tracheal bronchus and the blocker occludes the right mainstem bronchus.13,15
Typically, patients with tracheal bronchi presenting for intrathoracic procedures can be well managed with a left DLT. The DLT is the preferred technique because it provides excellent lung isolation, the ability to suction or isolate either bronchus, as well as a means to introduce continuous positive airway pressure to the operative lung. Furthermore, DLTs allow for bronchoscopic visualization of the bronchus during resection, without interrupting ventilation, to ensure a short surgical stump.
There are caveats in selecting a left DLT in patients presenting for left lung surgery. These caveats include (1) the necessity of retracting the DLT into the trachea before bronchial clamping during a left-sided pneumonectomy, and (2) the potential of obstructing the tracheal bronchus with the tracheal cuff of the DLT in patients with type I or II tracheal bronchi. A left-sided bronchial blocker may be more advantageous in these cases for the following reasons: (1) the large DLT and potential trauma with placement and postoperative reintubation with an SLT for bronchoscopy can be avoided, and (2) the tracheal cuff of the SLT can be adequately positioned to ensure ventilation of the tracheal bronchus, whereas the distance between the 2 cuffs of the DLT is a fixed distance.
If a DLT is not an option or is not ideal, one or more forms of bronchial blockers: SLT with isolated bronchial blocker, e.g., Arndt, Cohen Tip Deflecting Endobronchial Blocker® (Cook Critical Care, Bloomington, IN), Uniblocker (Vitaid, Lewiston, NY), Fogarty; or a blocker system, e.g., TCB Univent® Tube (Vitaid), may be required. Regardless of technique, ventilation of the tracheal bronchus should be preserved for left-sided operations.
Endobronchial advancement of a SLT or single-lumen endobronchial tube would be another potential solution. This technique would be best suited for right-sided procedures because right endobronchial placement of an SLT for a left-sided procedure would fail to ventilate the anomalous right upper lobe.
This report highlights the importance of a careful evaluation of the tracheobronchial anatomy with bronchoscopy before lung isolation, and reinforces the notion that anesthesiologists need to be flexible in their practice. One must tailor lung isolation to the surgical procedure and the patient's anatomy.
We are grateful to Marcia Williams, MSMI, for the illustrations in our article.
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