Tracheobronchomalacia (TBM) is an abnormal collapse of the tracheal and bronchial walls. It is characterized by flaccidity of the supporting tracheal and bronchial structures resulting in a significant reduction of airway diameter on expiration. This pathologic narrowing can produce dynamic outflow obstruction causing pulmonary symptoms that can mimic those of asthma, tracheal stenosis, foreign body aspiration, congestive heart failure, chronic obstructive pulmonary disease, anxiety disorder and pneumonia.
The incidence of TBM in adults has been reported to be as high as 23% among patients with COPD undergoing bronchoscopy. It has been shown in one study that TBM causes chronic cough and wheezing in 14% of nonsmoking patients.
Patients with TBM typically complain of wheezing, uncontrollable cough (described as a“barking cough” and with spells causing syncope/near syncope), dyspnea, orthopnea, recurrent pneumonia or bronchitis. In severe cases, patients present with choking episodes, stridor, respiratory failure and death. Many of these patients are erroneously labeled as having pulmonary symptoms of unknown etiology given that conventional computed tomography imaging, pulmonary function testing and oxygen saturation levels are normal in patients with TBM.
There are subtleties to each of these symptoms that make it more likely for these possibly generic symptoms to be more consistent with TBM than with other more common conditions (such as asthma or COPD). Most of these patients will describe having severe laryngopharyngeal reflux that has not been well controlled and typically has been present for years. Although no causal relation has been proven between reflux and TBM, review of the largest database in the world showed a preponderance of reflux disease in this patient population. Furthermore, once the tracheobronchomalacia is surgically corrected, recurrence has been seen primarily in patients with untreated (or unsuccessfully treated) reflux disease.
Often these patients are misdiagnosed with a severe anxiety disorder, which further limits their options of seeking further medical attention given that they are labeled as having a mental disorder. Many TBM patients report that bronchodilators do not improve their wheezing. In fact, some notice that their symptoms can worsen with the use of bronchodilators (as they facilitate the airway collapse).
A high degree of suspicion needs to be present when dealing with patients with “difficult to treat asthma or COPD”, as a classic example. One should consider the possibility of TBM and the patient should be referred to an interventional pulmonologist with expertise in this condition.
The gold standard for the diagnosis of TBM is dynamic flexible bronchoscopy. This protocol involves sequential dynamic maneuvers where the patient is asked to inhale and exhale while measurements are performed in the airways to measure the degree of airway collapse. Normal individuals can have up to 60% of dynamic collapse of the airway during forced exhalation. Therefore, accurate recording with video (or still photography) is necessary during bronchoscopy to precisely measure the change in airway diameter during inspiration and exhalation. In severe cases, this is not mandatory when it is obvious that the decree of collapse is near 100%.
The goal is to correct the excessive dynamic collapse. The ultimate treatment is surgical repair which requires a right posterolateral thoracotomy and placement of a marlex mesh carefully sutured onto the posterior tracheal membrane. This operation takes between 6 to 7 hours. Given the perioperative risks intrinsic to such surgery, it is mandatory to first stabilize the central airways with a silicone tracheobronchial stent. It is important to understand that metallic or hybrid (polyurethane covered metallic stents) stents have a black box warning imposed by the FDA and cannot be used for tracheobronchomalacia or similar benign conditions. The reason for this is that hybrid or metallic stents easily become epithelialized and cannot be easily removed if they are rejected by the patient’s airway (or if there is another reason to remove them). Furthermore, they are less durable than silicone stents and have a high index of fracture.
It is important to understand that silicone stents can only be deployed into the airway via rigid bronchoscopy and therefore only an interventional pulmonologist or thoracic surgeon facile at this skill can treat this condition. Furthermore, knowledge and finesse on how to manually tailor the silicone stent and how to place it to perfection is an additional skill necessary to be able to adequately treat these patients.
Dr. Guerrero deploys a Silicone Y shaped stent using rigid bronchoscopy to treat a patient with severe distal tracheal and bilateral bronchomalacia. The patient experienced complete resolution of his symptoms immediately following the procedure and was discharged home the same day of stent placement.
The patient is then seen following stent placement to assess if there is significant improvement of the symptoms. One would expect significant improvement prior to committing the patient to a thoracotomy with surgical repair of the trachea. Patients who improve with the stent and are good surgical candidates, will have the stent removed and they will move on to surgery. Those who improve with the stent but are deemed high risk due to other comorbidities, can keep the stent in place. However, it is important to note that the risk of stent obstruction and mucus plugging is high and the risks and benefits should be carefully assessed for each patient. Sequential bronchoscopic sessions are typically needed in order to keep the stent patent and patients should be placed on aggressive mucolytic and expectorant therapy.
As previously mentioned, it is important to understand that bronchodilators may worsen the degree of malacia and symptoms in some patients with TBM. Given that most of these patients are labeled as having asthma or “reactive airways disease”, they present for evaluation with a multitude of bronchodilators that may need to be promptly stopped (unless the patient unequivocally has concomitant severe asthma needing bronchodilation of the distal airways). Moreover, inhaled steroids may also put these patients at risk of respiratory infections given that these patients have an inability to clear secretions and are frequently colonized with bacteria in their airways.
Two prospective observational studies have demonstrated that airway stabilization of patients with severe TBM with silicone stents improves patient symptoms. The majority of patients demonstrate marked improvement in dyspnea, health-related quality of life and functional status. Improvement in cough is variable with the stent but reliable with surgical plication of the posterior membrane. It is paramount to note that these trials showed that even patients with severe parenchymal disease due to emphysema significantly benefit from stent placement followed by surgical correction with tracheobronchoplasty. In other words, having severe emphysema is not a contraindication to stent placement if the patient has concomitant severe TBM. A randomized, sham controlled rigid bronchoscopy and stent deployment trial is currently being contemplated. For the time being, patients should undergo a silicone stent trial as the first step in order to predict their response with definite surgical correction.
Tracheobronchomalacia is not a rare disorder. It is rather prevalent but remains under diagnosed and buried under the label of severe asthma, reactive airway disease or emphysema. Many patients are labeled as having anxiety disorder and most physicians give up on these patients. Unfortunately, even many Pulmonary and Critical Care fellowship programs (except for a very few centers with expertise in this condition) do not include teaching on how to diagnose and treat TBM. One reason for this is that the first prospective trial explaining how to diagnose and treat these patients was published after 2007. Fortunately, pulmonologists are starting to learn how to identify patients who may have TBM. This will allow some of these individuals to improve their quality of life when they are referred to a center that can provide proper diagnosis and treatment of this condition.
By Jorge Guerrero, MD, FCCP