- Tracheomalacia can be divided into segmental and diffuse malacia. Segmental malacia is usually a result of intubation cuff–related trauma. Pure segmental malacia is uncommon; rather, it is usually associated with adjacent areas of tracheal stenosis, creating complex so-called mixed lesions. It is best treated with definitive tracheal resection and primary anastomosis. Stenting with Montgomery T tubes provides a temporary or permanent alternative.
- Primary congenital tracheobronchomalacia (TBM) in newborns is most often seen in premature infants and results from immature cartilaginous and membranous components. Most children outgrow this condition by 1 to 2 years of age and can be managed with conservative measures.
- Diffuse forms of malacia in adults, such as acquired TBM and congenital Mounier-Kuhn syndrome, involve extensive regions of the airway and are best treated with restorative tracheobronchoplasty procedures. Overall results from the surgical treatment of malacic airways in properly selected patients is excellent.
- Adult patients with diffuse acquired TBM can be divided into two groups: nonsmokers with good lung capacity and long-time smokers with chronic obstructive pulmonary disease (COPD) and poor lung capacity. Patients with good lung capacity have almost uniform benefit from surgical repair. Patients with COPD require careful preoperative evaluation to screen out those whose functional status is limited by the small peripheral airway disease of COPD and will not sufficiently benefit from surgical correction of their TBM.
- A temporary trial of stenting with a silicone Y stent can be helpful in determining which patients are likely to benefit from definitive surgical correction. Stents are a poor long-term solution given their very high complication rate. They are difficult to manage and require constant maintenance. However, in selected cases, there may well be a place for internal stenting with silicone rubber tubes—T tubes, T-Y tubes, or Y tubes—as an alternative to external surgical stenting.
- As chronic dynamic airway computed tomographic (CT) imaging and functional bronchoscopic evaluations become more available, acquired TBM is being identified with increasing frequency. Further investigations need to focus on the prevalence of acquired TBM in the COPD population and define what role TBM plays in the debilitating dyspnea and recurrent pulmonary infections that COPD inflicts.
The normal trachea is relatively pliant and elastic, allowing its length and diameter to change under varying conditions. As the trachea enters the thoracic cavity, it is exposed to intrathoracic pressure variations that are opposite to those of the cervical trachea. The negative intrathoracic pressure created with inspiration creates a vacuum around the airway, leading to expansion of the intrathoracic trachea, while simultaneously creating a vacuum within the lumen of the cervical trachea, leading to its constriction. Forced expiration increases intrathoracic pressure, which causes compression of the intrathoracic trachea, while leading to an increase in intratracheal pressure, which causes cervical tracheal expansion (Figure 1). Consequently, structural tracheal defects affect the physiology of the cervical and thoracic portions of the trachea differently.
The normal trachea resists collapse by means of its semirigid, C-shaped anterior cartilaginous rings, which are bridged by the flat and muscular posterior membranous wall. At rest, the normal trachea is horseshoe or D shaped; with significant intrathoracic pressure increases (e.g., forceful expiration, coughing), the intrathoracic trachea is compressed, with lateral narrowing of the cartilaginous rings and mild to moderate anterior herniation of the membranous wall. In healthy individuals, this physiologic narrowing of airway diameter is functionally insignificant. It may, in fact, accelerate luminal air speed to assist with secretion clearance.
Malacia is defined as a softening or loss of consistency of a tissue or organ. Tracheomalacia is a pathologic increase in tracheal compliance that leads to a propensity to excessive airway collapse with physiologic intrathoracic pressure swings. The structural failure results from malacia of the cartilaginous rings, the posterior membranous wall, or both. In all cases, the end result is a dynamic airway obstruction causing dyspnea on exertion and difficulty raising secretions, with impaired pulmonary hygiene and recurrent pulmonary infections.
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