Tracheomalacia and tracheobronchomalacia in adults

INTRODUCTION — Tracheomalacia (TM) refers to diffuse or segmental tracheal weakness [1]. There are two distinct anatomical forms: cartilaginous malacia characterized by softening of the cartilage and membranous malacia with excessive anterior displacement of the membranous wall (also known as excessive dynamic airway collapse [EDAC]). Tracheobronchomalacia (TBM) exists when the weakness extends into one or both mainstem bronchi. Both conditions result in exaggerated luminal narrowing during expiration and widening during inspiration [2-5].

We refer to TM and EDAC collectively as TM in this review, since both conditions have a similar clinical presentation, diagnostic evaluation, and therapeutic approach [6], and the terms are frequently used interchangeably in practice. We distinguish between the disorders only when necessary.

The classification, epidemiology, histopathology, natural history, symptoms, diagnosis, and treatment of TM are reviewed here. TM in children is discussed separately. (See "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula".)

CLASSIFICATION — Several classification systems exist for TM:

●TM can be classified according to the appearance of the trachea:

•Crescent – Patients who have anteroposterior tracheal narrowing are said to have crescent (ie, scabbard shape) TM (figure 1).

•Lateral – Patients who have lateral tracheal narrowing are said to have saber-sheath (ie, fissure shape) TM (picture 1).

•Circumferential – Less frequently, some patients may have both anteroposterior and lateral narrowing and are said to have circumferential TM (picture 2).

●TM can be classified according to its distribution, as segmental or diffuse, tracheal, bronchial, or both. This is particularly useful for guiding therapy.

●TM can be classified as congenital (ie, primary) or acquired (ie, secondary) (table 1) [7,8]. Acquired TM is more common than congenital TM in adults.

Congenital — Congenital TM is the most common congenital tracheal abnormality and occurs in approximately 1:2100 children [9]. It can be seen in isolation or be associated with other abnormalities (laryngomalacia and laryngeal clefts) [10]. It may go unrecognized due to clinical features that overlap with more common pulmonary diseases.

Most types of congenital TM manifest during early childhood and are due to inherited diseases that weaken the trachea (eg, mucopolychondritis). Such disorders are discussed separately. (See "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula".)

There is a type of congenital tracheomegaly that typically presents during adulthood: idiopathic giant trachea (IGT). It is a rare condition caused by atrophy of the longitudinal elastic fibers and thinning of the muscularis mucosa [11]. IGT can also present as tracheobronchomegaly (Mounier-Kuhn syndrome) when the defect extends into the central bronchi [12]. The peripheral airways maintain a normal diameter [13]. Tracheobronchomegaly can be diagnosed when the diameter of the trachea, right mainstem bronchus, and left mainstem bronchus exceed 3.0, 2.4, and 2.3 cm, respectively (image 1) [14]. These measurements represent three standard deviations above the upper limit of normal in adults.

The cause of tracheobronchomegaly is uncertain but may be familial, at least partially [15]. Patients with tracheobronchomegaly mobilize their secretions poorly and, therefore, manifest chronic accumulation of secretions, cough, dyspnea, recurrent infections, bronchiectasis, and pulmonary fibrosis [11]. Tracheal diverticuli may develop due to the increased global compliance of the tracheal wall and the development of redundant membranous tissue [16,17]. (See 'Diagnosis' below and 'Treatment' below.)

Acquired — There are numerous causes of acquired TM in adults. Some of the more common causes are described in the table (table 1) [7].

●Tracheostomy or endotracheal intubation can damage the tracheal cartilage at the stoma or inflatable cuff site, respectively, which weakens the tracheal wall [7]. This type of TM is usually segmental, with a length of 3 cm or less (picture 3). Possible risk factors include recurrent intubation, prolonged intubation, concurrent high-dose steroid therapy, and cuff pressures >25 cm H₂O. The mechanism is uncertain but may include pressure necrosis, impaired blood flow, recurrent infections, mucosal friction, or mucosal inflammation [18].

●Other types of tracheal cartilage injury can also cause TM. These include external chest trauma and surgery (eg, lung transplantation) [19-21].

●Chronic compression of the trachea can cause TM. This is most commonly due to a benign mediastinal goiter [22]. However, it can also be due to malignancy, vascular compression, abscess, cyst, or other benign lesions.

●Relapsing polychondritis (RP) leads to the destruction of cartilage and is associated with TM (image 2) [23]. In one study, nearly 50 percent of patients with RP who were evaluated for airway involvement exhibited some degree of TM. Although RP affects males and females equally, severe airway manifestations are three times more likely in women [24].

●Recurrent infection might cause TM. Supporting this hypothesis, TM is common among adults who have chronic bronchitis or cystic fibrosis. In an observational study that included 40 adults with cystic fibrosis and 10 control subjects, TM was detected by computed tomography (CT) in 24 of the patients with cystic fibrosis (69 percent) and none of the controls [25].

●A substantial proportion of patients with severe emphysema and smokers (up to 5 percent) have TM, suggesting that chronic inflammation due to the inhalation of irritants (eg, cigarette smoke) may cause TM [26-28]. Recurrent infections and chronic use of a high dose of inhaled corticosteroids may also play a role [29].

●Other conditions and agents that may cause airway inflammation have also been associated with TM. Examples include exposure to mustard gas [30] and gastroesophageal reflux disease (GERD) [31,32].

EPIDEMIOLOGY — The prevalence of TM in adults is uncertain because reports have been based on selected populations instead of general populations. Older studies indicate that acquired TM is most common in men who are over 40 years of age [4,22,27,33,34]. These studies are supported by a study from Japan, in which 4283 patients with pulmonary disease underwent bronchoscopy [35]. The airway caliber narrowed more than 50 percent in 542 patients (12.7 percent). Among these patients, more than 70 percent were aged 50 to 80 years.

A meta-analysis looking at different diagnostic methods for TM showed a prevalence of 27 percent in patients with chronic obstructive airway disease (asthma and chronic obstructive pulmonary disease) and 17 percent of healthy subjects when the same 50 percent cutoff point was used during dynamic airway computed tomography scan, suggesting that more precise diagnostic criteria are needed to best correlate with relevant physiologic and disease sequelae [36].

HISTOPATHOLOGY — There is little known about the histopathologic changes associated with TM in adults. Autopsy studies have found anteroposterior narrowing of the lumen accompanied by atrophy of the longitudinal elastic fibers and fragmentation of the tracheal cartilage [27,33,35,37-39].

One study compared surgical resection specimens from patients with TM and tracheal stenosis (TS) with control tracheal specimens obtained from autopsy cases [40]. Airways of both patients with TM and TS had submucosal fibrotic changes, with TM specimens having alterations in elastin fiber quality and density in the posterior membrane. There was higher expression of fibroblast growth factor binding protein-2 and fibroblast growth factor receptor-3 in TM patients when compared with TS and controls, while expression of tumor growth factor-beta and tissue inhibitor of metalloproteinases-1 were also elevated when compared with controls.

NATURAL HISTORY — TM is progressive in most adult patients [2,27,41,42]. In a series of 17 patients with TM who underwent repeat bronchoscopy, worse airway narrowing was detected in 76 percent of patients [27]. A larger series followed 94 patients with TM, TBM, or bronchomalacia (BM) for an average of 5.2 years [42]. Among those who underwent repeat bronchoscopy, most patients had worse disease, some had stable disease, and none improved. Six of the nine patients with TM progressed to TBM, while all five patients with BM progressed to TBM.

CLINICAL MANIFESTATIONS — TM can be asymptomatic, especially if the airway narrowing is mild. However, symptoms or signs often develop as the severity of airway narrowing progresses, if the patient is challenged (eg, during an infection), or in certain clinical situations (eg, general anesthesia, progressive hypercapnic respiratory failure, liberation from mechanical ventilation) [43,44].

The major symptoms and signs of TM in adults are dyspnea, cough, and sputum retention [2]. Severe paroxysms of coughing may interrupt daily activities. Wheezing or stridor may also exist. An associated barking cough (likened to a barking seal) has been reported and some patients report episodic choking, recurrent pulmonary infections, or syncope associated with forced exhalation or cough [45-49]. Maneuvers can sometimes elicit signs of TM, including forced expiration, cough, a Valsalva maneuver, and certain positions (eg, recumbency).

These symptoms and signs are nonspecific and are often attributed to alternative diagnoses including emphysema, chronic bronchitis, bronchiectasis, cigarette smoking, or asthma. When TM coexists with one or more of these conditions, the symptoms may seem out of proportion to the severity of any condition alone or some patients may remain symptomatic despite maximal medical therapy for the condition being treated.

DIAGNOSIS — Bronchoscopic visualization of dynamic airway collapse is considered by many experts the diagnostic gold standard. Some experts also consider the demonstration of dynamic airway collapse on forced-expiratory computed tomography (CT) as diagnostic, although more research is needed to define exact parameters that accurately predict the diagnosis.

Diagnostic tests — Diagnostic modalities that are used to evaluate suspected TM include dynamic flexible bronchoscopy (DFB), dynamic airway computed tomography (DACT), and pulmonary function testing (PFT).

Bronchoscopy — Bronchoscopic visualization of dynamic airway collapse is considered by many experts the diagnostic gold standard. DFB is performed under minimal sedation with fentanyl, midazolam, and local anesthesia (1 percent lidocaine) when the patient can breathe spontaneously and follow commands. In a pilot study, there was favorable inter-and intra-observer agreement among 23 pulmonologists using DFB to estimate the degree of airway collapse [50]. (See "Flexible bronchoscopy in adults: Preparation, procedural technique, and complications".)

Historically, TM was diagnosed if there was >50 percent decrease in airway lumen size, but data from healthy volunteers have shown that this threshold was met in up to 78 percent [50,51]. For this reason, we use a more rigorous criterion to diagnose TM and have changed our thresholds to normal if the operator estimates that the lumen narrows by <70 percent of its initial size during expiration, mild if it narrows by 70 to 80 percent, moderate if it narrows by 81 to 90 percent, and severe if it narrows by >90 percent or the anterior and posterior walls touch (picture 4). 

Some studies used deep breathing, forced expiration, Valsalva maneuvers, cough, and other maneuvers to elicit airway collapse during bronchoscopy. However, the significance of airway collapse in response to such maneuvers is unknown because the degree of airway collapse and the amount of expiratory effort have never been correlated and sometimes such maneuvers can induce bronchospasm.

Computed tomography — CT may be useful in the diagnosis of TM with reported accuracy rates as high as 97 percent [52-55]. A high-quality study requires patient cooperation and coordination with radiology staff. An adequate dynamic expiratory image should include the following findings: (1) the posterior tracheal wall will be flat or bowed forward, (2) a smaller anteroposterior airway diameter, and (3) an increase in lung attenuation. Dynamic CT scan of the central airways includes images at the end of inspiration and during forced expiration taken in a caudal-cranial direction. To calculate the degree of airway collapse or collapsibility index (CI), the dynamic expiratory area (DEA) is subtracted from the area at end inspiration (AEI) and this number is then divided by the AEI and multiplied by 100. CI = (AEI-DEA/AEI) x 100 (image 3) [56]. Criteria for diagnosing TM by CT are currently the same as those for diagnosing TM by bronchoscopy (image 4). The airways are measured in cross-section on images obtained at end-expiration.

Diagnostic assessment by CT requires additional study and refinement before CT surpasses bronchoscopy as the diagnostic gold standard. At least one observational study has found that CT can reliably predict TM, especially when the predictive measure is the degree to which the sagittal diameter decreases from end-inhalation to end-exhalation [53]. However, the current diagnostic criterion of greater than 50 percent luminal narrowing may not be the optimal diagnostic threshold, since it is met in up to 78 percent of asymptomatic control subjects during forced exhalation [51]. The findings from the latter study underscore the variability of the normal collapsibility of the trachea. More research is needed to define what threshold might be used during CT evaluation to accurately predict clinically significant collapse of the airway.

Ultrafast multidetector CT scanners permit volumetric central airway imaging in only a few seconds. This allows true dynamic assessment of TM because the airway can be imaged during a forced exhalation or cough maneuver [57]. In addition, a retrospective study showed that using an ultra-low dose (ULD) CT scan technique when compared with a typical dose CT scan maintained a good diagnostic image while using a low effective dose of less than 0.1 mSv. Although the results of this study seem to be promising further studies are needed to validate the diagnostic accuracy of this new technique [58].

Chest CT is also an excellent tool for visualizing diseases external to the airway that can cause focal malacia such as substernal goiters and vascular rings/slings.

Pulmonary function tests — PFTs can provide data supportive of a diagnosis of TM, but they are not diagnostic. Spirometry usually demonstrates obstruction that is proportional to the severity of the TM [42,52]. In a descriptive study of 90 patients with moderate to severe TBM who underwent PFTs, 44 percent of patients had an obstructive ventilatory defect, 18 percent had a definite or highly likely restrictive ventilatory defect, 17 percent had a mixed defect, and 21 percent were within normal limits [59].

The flow-volume loop (FVL) is characterized by a low peak expiratory flow rate followed by a rapid decrease of flow (figure 2). In one study, the most frequent finding was low FEFmax in 82 percent of cases, followed by biphasic morphology 20 percent, notched expiratory loop 9 percent, expiratory oscillations (alternating decelerations and accelerations of flow) 3 percent, and 17 percent had no distinctive FVL abnormality (figure 3) [59]. However, in a retrospective review of 2800 flow-volume loops, flow oscillations were identified in 40 patients (1.4 percent) [60]. Physiological upper airway obstruction was detected in 14 of these patients (35 percent). These oscillations can be caused by TM, redundant pharyngeal tissue, neuromuscular disease, or structural or functional disorders of the larynx and are not diagnostic of TM [61,62].

Chest radiography — Airway narrowing or dilation due to TM is a dynamic process, occurring at certain points during the respiratory cycle. Thus, routine anteroposterior and lateral chest radiographs often do not show an abnormality. In circumstances in which the TM is caused by compression from other structures (eg, mediastinal goiter), the underlying abnormality may be detectable on the chest radiograph [7].

Diagnostic approach — TM may be suspected based on a patient's symptoms and signs. Alternatively, it may be suspected based on PFT results or a chest imaging that was performed for evaluation of the related symptoms and signs.

Once TM is suspected, the patient should undergo both dynamic CT and bronchoscopy with forced exhalation maneuvers to evaluate the degree of TM and bronchomalacia (BM). Both tests are necessary because either test alone may underestimate the degree of TM. As an example, sedation for bronchoscopy may prevent maximal effort during a forced exhalation maneuver, thereby underestimating the severity of the dynamic airway collapse. If the forced exhalation maneuver is repeated during a CT scan when the patient is not sedated, the collapsibility of the airway may be more accurately determined. On the other hand, if the CT image is taken during end exhalation rather than during the forced exhalation maneuver it may underestimate the degree of collapse [63] and this may be more accurately assessed during dynamic flexible bronchoscopy.

CT and bronchoscopy have unique advantages. CT is better able to show the distal extent of the TM when it extends into the segmental and subsegmental bronchi. This has implications for treatment since neither stenting nor surgical options can correct the distal disease. CT scan also provides objective measurements of anterior-posterior and lateral dimensions as well as cross-sectional area. Bronchoscopy provides information about the presence of coexisting conditions (paradoxical vocal fold motion, laryngopharyngeal reflux, and airway infection or inflammation) as well as the ease of navigation into and within the airways, which is useful for planning future interventions.

The severity of TM is determined as described above. (See 'Bronchoscopy' above and 'Computed tomography' above.)

Additional investigations — Once the diagnosis is made, we routinely also perform the following:

●Laryngoscopy – Laryngoscopy is performed to evaluate for vocal cord dysfunction (VCD) since the prevalence of VCD is high in patients with TM.

●Esophageal pH impedance study – Esophageal impedance is performed to evaluate for significant gastroesophageal reflux disease (GERD) since GERD is also prevalent in this population [32].

Occasionally, immunoglobulin levels are performed in those with recurrent infections to evaluate for the presence of immunoglobulin deficiency.

TREATMENT

General approach — A useful approach to the management of TM is shown in the algorithm (algorithm 1). First, it is determined whether a patient with TM is symptomatic. Asymptomatic patients generally do not require therapy, whereas therapy may be warranted for symptomatic patients.

Initial treatment of symptomatic patients targets the underlying cause of the TM and coexisting conditions. Patients with coexisting asthma or chronic obstructive pulmonary disease (COPD) can improve, if their medical regimen is optimized, by decreasing the degree of bronchospasm and large pressure swings in the thorax that worsen the collapse of the central airways. The treatment of gastroesophageal reflux and diseases such as relapsing polychondritis reduces airway inflammation and symptoms and may slow the progression of the disease. Following optimization of all coexisting conditions, a functional assessment is performed (pulmonary function tests [PFTs], six-minute walk test, quality of life assessment, dyspnea, and cough scores) in patients who remain symptomatic [1]. The purpose of this assessment is to establish a baseline from which the response to therapy can be "objectively" measured, bearing in mind that all of these measurements include subjective effort or assessment, and placebo-controlled trials have not been performed in this population.

We insert airway stent(s) (eg, A y-silicone stent or uncovered self-expanding metallic stents [USEMAS]) for one to two weeks, as a means of identifying patients who are most likely to benefit from central airway stabilization. This is frequently referred to as a stent trial; importantly these "trial stents" should not be left in for a prolonged period, especially USEMAS as they have a black box warning against their use in the treatment of benign airway disease.

●Patients who are not surgical candidates, but who objectively improve following stent insertion, may be managed with intermittent continuous positive airway pressure (CPAP) and additional therapies (listed below) and/or long-term stenting (using silicone stents). Due to a high incidence of stent-related complications (mucus plug or granulation tissue formation), it is recommended that these patients have a close clinical and bronchoscopic follow-up.

●Patients who are surgical candidates and objectively improve following stent insertion can be referred for definitive surgical repair at a center with significant experience in tracheobronchoplasty (TBP).

●Patients who do not improve with stenting should have the stents removed. No intervention may, in this case, be offered and other causes for the symptoms should be investigated.

It is important to emphasize that improvement or lack of improvement following the insertion of airway stents needs to be objectively demonstrated and documented before the long-term intervention is chosen and implemented.

An exception to this approach exists when the primary symptom of the TM is not dyspnea. Examples include patients whose primary symptom is severe paroxysmal cough or recurrent infection (more than three per year). In such cases, a stent trial probably will not yield improvement and the decision regarding surgery must be made based on symptoms and abnormal anatomy alone.

Stenting — Relief of focal airway obstruction via stenting often provides immediate improvement of both airflow and symptoms according to several case series and observational studies [19-21,64-66], although these findings have not been universal [67]. The main role of airway stents in patients with diffuse symptomatic TBM is to help identify patients that will benefit from surgical airway stabilization (TBP), through a one to two-week stent trial. In highly selected cases, long-term custom-made y-silicone stents may be used to treat those patients who have shown subjective and objective improvement during the stent trial, and do not develop stent-related complications and are not surgical candidates.  

Silicone stents are preferred for the chronic management of TM. Although their insertion requires rigid bronchoscopy and general anesthesia, they are easily repositioned and removed. Their major disadvantage is that tubular silicone stents often migrate or plug with mucus, which generally manifests as a new cough, hoarseness, or dyspnea. Stent migration requires repositioning, removal, or replacement of the stent, while mucus plugging will need a bronchoscopic aspiration of secretions under direct visualization. More recently, silicone Y-shaped stents are used and migration can be prevented when compared to previous tubular silicone stents. However, other stent-related complications (eg, infection, cough, mucus-plugging, and granulation tissue formation) occur with similar frequency [65,66].

Metal stents have been used to manage many types of airway obstruction [68,69]. Metal stents have some advantages, including easy placement by flexible bronchoscopy, dynamic expansion, and preservation of mucociliary function. A retrospective study of 33 patients with severe symptomatic TBM showed that the short-term use of USEMAS improved respiratory symptoms, quality of life, and exercise capacity with few complications [70]. For this reason, USEMAS have become our preferred stent to help identify patients who would benefit from surgery. However, long-term use is not recommended for benign airway obstruction. In addition, they are a poor choice for the long-term treatment of TM because they cannot be easily removed and are associated with numerous complications such that the US Food and Drug Administration has issued a black box warning regarding their use [71,72]. As such, we recommend their use only in centers of excellence and where patient follow-up is guaranteed. Potential complications include the formation of granulation tissue and breakage [2]. The latter can cause severe problems including airway obstruction and perforation (picture 5). Airway stenting is discussed in detail separately. (See "Airway stents".)

Surgical repair — Several surgical treatments for TM have been described, primarily in case series [37,73-79].

●Tracheobronchoplasty (TBP) refers to surgical splinting of the posterior wall of the trachea with polypropylene mesh [79]. It is the definitive operative treatment for TM. When an open approach is used, a right posterolateral thoracotomy is used to approach both the thoracic trachea and bilateral bronchi. Polypropylene mesh is sutured to the posterior membranous wall and anchored to the cartilaginous edges of the trachea and bronchi. The sutures are placed in a partial-thickness fashion, resulting in a posterior splint that is entirely external to the airway lumen. This splint reconstitutes a C-shape to the tracheal cartilage and prevents the posterior membrane from intruding into the lumen (picture 6 and image 5). A prospective study that followed 35 patients with severe symptomatic TM for three months following TBP found that quality of life, dyspnea, mean exercise capacity, and functional status significantly improved following the procedure, compared with baseline [78]. Another retrospective study from the same group included 63 patients who underwent TBP and showed a clinical and statistical improvement in functional status, quality of life, dyspnea, and exercise capacity at three months [80].

●TBP can also be performed using a robotic approach. A retrospective study including 42 patients that underwent robotic TBP (R-TBP) showed that at a median follow-up of 40 months, there were no signs or symptoms of mesh infection or erosion. Patients that underwent R-TBP had a significant improvement in dyspnea-related quality of life as measured by the Saint George Respiratory Questionnaire and mean PFT values at a median follow-up of 29 months [81].  

●Conventional resection and reconstruction are utilized in cases of focal malacia, most commonly in the cervical trachea. It has low morbidity and mortality in experienced hands and provides curative relief without the need for multiple endoscopic interventions. However, like any resection of the trachea, it can have the unintended consequence of renarrowing the trachea (ie, tracheal stenosis).

●Tracheal replacement refers to the replacement of the defective trachea with a new trachea made from foreign material, donor tissue, nonviable tissue, autogenous tissue, or engineered tissue [82,83]. It has been considered for decades, but a reliable tracheal replacement has not been developed [84].

Tracheostomy — Tracheostomy alone may be effective if the tracheostomy tube bypasses the abnormal tracheal segment or splints the abnormal airway open. Longer segments of TM may require longer tracheostomy tubes. Even if the TM is diffuse, tracheostomy may be beneficial as a route to deliver positive airway pressure.

A Montgomery T-tube is a type of stent. It has a narrow tube that connects at a right angle to a larger tube, forming the shape of the letter T. The narrow tube passes from the tracheal lumen through a cervical stoma, similar to a standard tracheostomy tube. The larger tube functions like a straight tubular tracheal stent extending both superior and inferior to the stoma. The inferior aspect of the larger tube can extend into the thoracic trachea. The airflow during breathing is through the lumen of the larger tube and the larynx if the narrow tube is capped externally. In contrast, the airflow is through both the narrow tube and the larynx if the narrow tube is uncapped. Occasionally, a silicone tracheal T-tube is used for long-term stenting, especially if the malacic segment is in the cervical or upper thoracic trachea (picture 3).

Tracheostomy itself can worsen TM by destroying the tracheal cartilage and weakening the tracheal wall. For this reason, tracheostomy is a treatment of last resort.

Positive pressure — CPAP can maintain an open airway and facilitate secretion drainage [18,85,86]. This is often initiated in the hospital during an acute illness. The patient initially receives continuous CPAP and is gradually transitioned to intermittent CPAP as tolerated.

Patients may use intermittent CPAP as long-term therapy. However, CPAP does not appear to have a long-term impact on dyspnea or cough [18,85]. The use of automatically adjusting positive airway pressure (APAP) should be used with caution unless it is clear that the minimum pressure provides adequate support. Other types of positive airway pressure, specifically bilevel positive airway pressure should be used if hypercapnic respiratory failure exists.

In highly selected patients we recommend the use of CPAP to facilitate pulmonary rehabilitation prior to surgery or long-term in patients who are deconditioned and are not surgical candidates due to comorbid conditions.

Additional therapies

●Airway clearance techniques – Retained secretions are an important cause of recurrent infections, airway obstruction, and airway/lung injury. In order to minimize mucostasis, we typically use airway oscillatory devices (flutter valve) or external percussion vests twice or three times per day.

●Pulmonary rehabilitation – For patients with dyspnea and deconditioning we often refer patients to pulmonary rehabilitation regardless of whether the airway has undergone an intervention or not.  

●Breathing techniques – All patients with severe TBM should be educated in the pursed lip breathing (PLB) technique. PLB is a breathing technique that consists of exhaling through tightly pressed lips and inhaling through the nose with the mouth closed. The purpose of this technique is to create pressure inside the airways thus producing a pneumatic split during exhalation and decreasing the work of breathing.

Investigational therapies — Case series have shown promising results when using thermoablative techniques (ie, holmium laser) to treat the posterior membrane wall of patients with excessive dynamic airway collapse (EDAC) morphology [87,88]. Despite promising initial results, additional evidence is needed to recommend the use of bronchoscopic thermoablative techniques in this patient population.

While preclinical data in sheep suggest that argon plasma coagulation (APC) may be a feasible modality for thermoablation compared with electrocautery, radiofrequency ablation, and potassium titanyl phosphate laser [89,90], human trials are needed to demonstrate the feasibility and effectiveness of APC treatment of the posterior membrane wall in patients with EDAC.

SUMMARY AND RECOMMENDATIONS

●Introduction and terminology – Tracheomalacia (TM) refers to diffuse or segmental tracheal weakness. There are two distinct anatomical forms, cartilaginous (TM) and membranous (excessive dynamic airway collapse [EDAC]). Tracheobronchomalacia (TBM) exists when the weakness extends into one or both mainstem bronchi. Both conditions result in exaggerated luminal narrowing during expiration and widening during inspiration. TM and EDAC have similar clinical presentation, diagnostic evaluation and treatment and for that reason the terms are often used interchangeably. (See 'Introduction' above.)

●Clinical manifestations – TM can be asymptomatic, especially if the airway narrowing is mild. However, symptoms and signs frequently develop as the severity of airway narrowing progresses, if the patient becomes challenged, or in certain clinical situations. The major symptoms and signs of TM in adults are dyspnea, cough, sputum retention, expiratory wheezing or stridor, and recurrent respiratory infections. (See 'Clinical manifestations' above.)

●Diagnosis – Dynamic computed tomography (CT) and bronchoscopy with forced exhalation maneuvers should both be performed when TM is suspected. Criteria for the diagnosis of TM are the same, regardless of which test is used to measure luminal narrowing. (See 'Diagnosis' above.)

•TM is diagnosed if there is >70 percent decrease in airway lumen.

•TM is classified as the following:

-Mild if the lumen narrows 70 to 80 percent of its initial size during expiration,

-Moderate if it narrows by 81 to 90 percent of its initial size,

-Severe if it narrows by >90 percent or the anterior and posterior walls touch (picture 4).

●Management – Therapy is warranted in symptomatic patients with severe TM, but not asymptomatic patients. Initial treatment targets the underlying cause of the TM and all coexisting conditions that may be contributing to the symptoms. Patients who remain symptomatic after initial therapy should undergo a functional assessment (pulmonary function tests, six-minute walk test, dyspnea and cough score). This functional assessment provides a baseline from which treatment response can be measured. (See 'Treatment' above and 'General approach' above.)

•For patients who remain symptomatic after initial therapy, we suggest a stent trial as the next therapy (Grade 2C). (See 'General approach' above and 'Stenting' above.)

•For patients who improve following stent insertion, but are not surgical candidates, we suggest long-term stenting with a custom made Y-silicone stent with close bronchoscopic follow up to identify stent related complications (like granulation tissue formation) (Grade 2C). (See 'Stenting' above.)

•For patients who improve following stent insertion and are surgical candidates, we suggest evaluation for definitive surgical correction (Grade 2C). Tracheobronchoplasty (open or robotic) is the definitive operative technique for most patients. This should take place in medical centers with specific expertise in this procedure. (See 'Surgical repair' above.)

•For patients who do not improve after stent insertion, we suggest that the stents be removed (Grade 2C) and diagnostic workup is recommended to help identify an alternative cause for the patients symptoms. (See 'Tracheostomy' above and 'Positive pressure' above and 'Additional therapies' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Armin Ernst, MD, FCCP, Kelly Carden, MD, and Sidhu Gangadharan, MD, who contributed to an earlier version of this topic review.