Tracheobronchomalacia

State-of-the-art narrative review: Mounier-Kuhn syndrome and tracheobronchomegaly

Mounier-Kuhn syndrome (MKS) or tracheobronchomegaly is an uncommon disease of the central airways. It is characterized by pathological dilatation of the trachea and main bronchi and inevitably leads to recurrent respiratory infections, bronchiectasis, hospitalizations, and results in considerable morbidity and mortality. Despite numerous case reports, there is a shortage of evidence on clinical outcomes and limited data on interventions, thus presenting a significant gap in the literature. Fortunately, new strategies and increasing clinical experience have improved the clinical approach, diagnostic workup, classification, and management of MKS. Articles in English, Spanish, and French were searched from databases, including Pubmed, Google Scholar, Medline, and SCOPUS, using the terms "Mounier-Kuhn syndrome," "Tracheomegaly," "Tracheobronchomegaly," and "Bronchomegaly," without date restrictions. A total of 360 articles with the aforementioned syntax were indexed on Pubmed. This state-of-the-art review attempts to fill a void in the current literature by summarizing the current scientific knowledge and highlighting novel interventional strategies in the management of Mounier Kuhn Syndrome.

Sedation during dynamic bronchoscopy for expiratory central airway collapse: Which is the ideal protocol?

OBJECTIVE

To compare sedation protocols for dynamic bronchoscopy (DB) in the evaluation of expiratory central airway collapse (ECAC).

MATERIALS AND METHODS

This observational study included adult patients (≥18 years) referred to Mayo Clinic, Jacksonville, FL, from March 2023 to July 2024, for suspected ECAC. Patients were grouped based on sedation protocols: propofol (Protocol 1), remimazolam (Protocol 2), and remimazolam/fentanyl (Protocol 3). The primary outcome was the quality of assessment during DB, rated on a 4-point Likert scale (1 = poor, 4 = excellent). Secondary outcomes included anesthesia duration and post-anesthesia care unit (PACU) length of stay. Statistical analyses included Fisher's exact test, ordinal logistic regression, and Kruskal-Wallis tests.

RESULTS

Seventy-three patients met the inclusion criteria. Overall, DB quality of assessment was significantly associated with sedation protocol (P=0.01 Ordinal regression results suggest that protocol 3 (remimazolam/fentanyl) may be comparable to protocol 1 (propofol) (OR0.40, 95%CI 0.12-1.33, P = 0.13), with both showing a tendency for better performance than protocol 2 (remimazolam) (OR0.14, 95%CI 0.04-0.46 P=0.002 vs protocol 3; OR0.35, 95%CI 0.09-0.29 P=0.115 vs protocol 1). No significant differences were found in PACU length of stay among the three protocols (P = 0.13). No post-procedural complications were reported.

CONCLUSION

Protocol 3 (remimazolam/fentanyl) demonstrated significantly higher odds of achieving a better quality of assessment compared to Protocol 2 (remimazolam) and showed comparable performance to Protocol 1 (propofol). These findings suggest that remimazolam/fentanyl is an effective sedation option for DB, providing improved assessment quality without increasing PACU stay. Larger prospective studies are necessary to confirm these results.

Adult Tracheobronchomalacia that Progressed Following Radiotherapy in an Advanced-stage Lung Cancer Patient: A Rare Case Report

Tracheobronchomalacia (TBM) is the collapse of the trachea and bronchi, which leads to respiratory symptoms and complications, often on forced expiration. Radiotherapy (RT) is a rare cause of adult TBM. Here, we report the first case of progressive TBM following palliative RT in a patient with squamous cell lung carcinoma. TBM was diagnosed by fiberoptic bronchoscopy and thoracic CT scans. In patients with advanced-stage lung cancer who experience worsening dyspnea and cough following palliative RT, TBM should also be taken into account.

Assessment of MMP-9 and clinical characteristics in dogs with tracheal collapse based on cough severity and fluoroscopic findings: a cross-sectional study

BACKGROUND

Tracheal collapse (TC), a common disease in dogs, is characterized by cough; however, little is known about the serum biomarkers that can objectively evaluate the severity of cough in canine TC. Furthermore, studies elucidating the relationship of fluoroscopic characteristics with the severity of cough are lacking. Therefore, this study aimed to evaluate the relationship between cough severity and clinical characteristics, fluoroscopic images, and new serum biomarkers in canine TC.

RESULTS

Fifty-one client-owned dogs diagnosed with TC based on fluoroscopic and clinical signs were enrolled in this study and divided into three groups according to the severity of cough (grade of cough: 0, 1, and 2). Signalments, comorbidities, and fluoroscopic characteristics were compared among the groups retrospectively. The serum matrix metalloproteinase-9 (MMP-9), interleukin-6 (IL-6), surfactant protein-A (SP-A), and syndecan-1 (SDC-1) levels were measured in all groups. No significant differences in age, breed, sex, or clinical history were observed among the groups. Concomitant pharyngeal collapse increased significantly with the severity of cough (p = .031). Based on the fluoroscopic characteristics, the TC grade of the carinal region increased significantly and consistently with the grade of cough (p = .03). The serum MMP-9 level was significantly higher in the grade 2 group than that in the grade 0 group (p = .014). The serum IL-6 level was significantly lower in the grade 1 group than that in the grade 0 group (p = .020). The serum SP-A and SDC-1 levels did not differ significantly among the groups.

CONCLUSIONS

The severity of cough with the progression of TC can be predicted with the fluoroscopic TC grade at the carinal region. MMP-9 may be used as an objective serum biomarker that represents cough severity to understand the pathogenesis.

[Interventionnal bronchoscopy for the treatment of tracheobronchomalacia]

Tracheobronchomalacia is usually characterized by more than 50% expiratory narrowing in diameter of the trachea and the bronchi. The expiratory collapse includes two entities: (1) the TBM related to the weakness of the cartilaginous rings, and (2) the Excessive Dynamic Airway Collapse (EDAC) due to the excessive bulging of the posterior membrane. Patients have nonspecific respiratory symptoms like dyspnea and cough. Diagnosis is confirmed by dynamic tests: flexible bronchoscopy and/or computed tomographic scan of the chest. There are different forms of tracheobronchomalacia in adults: primary (genetic, idiopathic) or secondary to trauma, tracheotomy, intubation, surgery, transplantation, emphysema, infection, inflammation, chronic bronchitis, extrinsic compression; or undiagnosed in childhood vascular rings. Some management algorithms have been proposed, but no specific recommendation was established. Only symptomatic patients should be treated. Medical treatments and noninvasive positive pressure ventilation should be the first line therapy, after evaluation of various quality measures (functional status, performance status, dyspnea and quality of life scores). If symptoms persist, therapeutic bronchoscopy permits: (1) patient's selection by stent trial to determine whether patient benefit for surgical airway stabilization; (2) malacic airways stenting in patients who are not surgical candidates, improving QOL despite a high complication rate; (3) the management of stent-related complication (obstruction, plugging, migration granuloma); (4) alternative therapeutics like thermo-ablative solution. Lasty, the development of new types of stents would reduce the complication rates. These different options remained discussed.

Thermoablative Techniques to Treat Excessive Central Airway Collapse

Excessive central airway collapse (ECAC) is a condition characterized by the excessive narrowing of the trachea and mainstem bronchi during expiration, which can be caused by Tracheobronchomalacia (TBM) or Excessive Dynamic Airway Collapse (EDAC). The initial standard of care for central airway collapse is to address any underlying conditions such as asthma, COPD, and gastro-esophageal reflux. In severe cases, when medical treatment fails, a stent-trial is offered to determine if surgical correction is a viable option, and tracheobronchoplasty is suggested as a definitive treatment approach. Thermoablative bronchoscopic treatments, such as Argon plasma coagulation (APC) and laser techniques (potassium-titanyl-phosphate [KTP], holmium and yttrium aluminum pevroskyte [YAP]) are a promising alternative to traditional surgery. However, further research is needed to assess their safety and effectiveness in humans before being widely used.

Improvement in postoperative lung function in patients with moderate to severe airway obstruction after robotic-assisted thoracoscopic tracheobronchoplasty

OBJECTIVE

The study objective was to examine pulmonary function and quality of life improvement after robotic-assisted thoracoscopic tracheobronchoplasty for patients with different degrees of obstructive airway disease.

METHODS

We performed a retrospective review of a prospective database of patients who underwent robotic-assisted thoracoscopic tracheobronchoplasty between 2013 and 2020.

RESULTS

A total of 118 patients underwent robotic-assisted thoracoscopic tracheobronchoplasty. Preoperative and postoperative pulmonary function tests were available for 108 patients. Postoperative pulmonary function tests at a median of 16 months demonstrated a significant increase in percent predicted forced expiratory volume in 1 second (preoperative median: 76.76% predicted, postoperative: 83% predicted, P = .002). Preoperative and postoperative St George Respiratory Questionnaires were available for 64 patients with a significant decrease in postoperative score at a median of 7 months (preoperative median: 61, postoperative: 41.60, P < .001). When stratified by preoperative degree of obstruction, robotic-assisted thoracoscopic tracheobronchoplasty improved forced expiratory volume in 1 second in moderate to very severe obstruction with a statistically significant improvement in moderate (preoperative median: 63.91% predicted, postoperative median: 73% predicted, P = .001) and severe (preoperative median: 44% predicted, postoperative median: 57% predicted, P = .007) obstruction. St George Respiratory Questionnaire scores improved for all patients. Improvement for mild (preoperative median: 61.27, postoperative median: 36.71, P < .001) and moderate (preoperative median: 57.15, postoperative median: 47.52, P = .03) obstruction was statistically significant.

CONCLUSIONS

Robotic-assisted thoracoscopic tracheobronchoplasty improves obstruction and symptoms. With limited follow-up, subgroup analysis showed forced expiratory volume in 1 second improved in severe preoperative obstruction and quality of life improved in moderate obstruction. Future follow-up is required to determine robotic-assisted thoracoscopic tracheobronchoplasty effects on the most severe group, but we cannot conclude that increased degree of preoperative obstruction precludes surgery.

Isolated Tracheabronchomalacia Misdiagnosed for Years as Bronchial Asthma

Tracheomalacia (TM) is an abnormal collapse of the tracheal lumen, which often occurs when the cartilaginous part of the trachea has not developed. It is a rare condition but is seen often in infancy and childhood period. The incidence of primary airway malacia in children was estimated to be at least one in 2,100. It has a wide range of etiologies, and it is often localized but rarely generalized as in our case. It could be severe enough to indicate frequent admission and might expose the patient to multiple unnecessary medications. We are reporting a case with unusual primary tracheobronchomalacia (TBM) that was missed for several years with a huge burden on both families and healthcare providers. A five-year-old Saudi girl had multiple admissions to the intensive care unit with similar presentation each time, and she was misdiagnosed as having asthma exacerbation with an occasional chest infection. Bronchoscopy revealed the underlying condition, and the patient was kept on the minimal intervention of nasal continuous positive airway pressure (CPAP) and aggressive airway hydration therapy, all with the goal of improving the patient's outcome and reducing hospital admissions. We emphasize the importance of alerting physicians about malacia as an important cause of recurrent wheezy chest, which is one of the common asthma mimickers; in such cases, flexible bronchoscopy remains the gold standard diagnostic test, while the treatment remained supportive.

Stent Evaluation for Expiratory Central Airway Collapse: Does the Type of Stent Really Matter?

BACKGROUND

Careful selection of patients with expiratory central airway collapse (ECAC) that may benefit from tracheobronchoplasty (TBP) can be aided by a short-term airway stent evaluation. This can be performed with either silicone Y-stents (SYSs) or uncovered self-expanding metallic airway-stents (USEMAS). No direct comparison has been made between these 2 stent types.

METHODS

This was a small retrospective review of consecutive patients that underwent a stent evaluation. A propensity score was used to match patients in the USEMAS and SYS groups. Outcomes included complications, changes in the health-related quality-of-life (HR-QoL), and changes in exercise capacity. Baseline measurements were compared with those obtained during stent evaluation and after TBP.

RESULTS

Forty-two patients with severe ECAC underwent USEMAS placement, while 18 patients had an SYS placed. Propensity score matching resulted in 13 matched SYS and USEMAS pairs. The SYS group had an increased rate of mucus plugging (38.5% vs. 0%, P <0.047). Although not statically significant, a clinical improvement was observed in HR-QoL and exercise capacity in the USEMAS group during stent placement. In patients who underwent TBP, both USEMAS and SYS groups had a statistically significant change in the Modified Medical Research Council Dyspnea Scale during stent evaluation and after TBP.

CONCLUSION

In patients with severe ECAC, short-term evaluation with airway stents appears to be safe and improves respiratory symptoms, HR-QoL, and exercise capacity. The use of USEMAS led to a lower complication rate, a greater improvement in HR-QoL and exercise capacity, and appeared to better predict how the patients would respond to TBP.

Expiratory central airway collapse during positive pressure ventilation: a case report

Background

Physiologic narrowing of the central airway occurs during expiration. Conditions in which this narrowing becomes excessive are referred to as expiratory central airway collapse. Expiratory central airway collapse is usually managed by applying positive pressure to the airways, which acts as a pneumatic stent. The particularity of the case reported here included the patient’s left main bronchus being permeable during spontaneous breathing but collapsing during general anaesthesia, despite positive pressure ventilation and positive end-expiratory pressure.

Case presentation

We present the case of a 55-year-old man admitted for the placement of a ureteral JJ stent. Rapid desaturation occurred a few minutes after the onset of anaesthesia. After excluding the most common causes of desaturation, fibreoptic bronchoscopy was performed through the tracheal tube and revealed complete collapse of the left main bronchus. The collapse persisted despite the application of positive end-expiratory pressure and several recruitment manoeuvres. After recovery of spontaneous ventilation, the collapse was lifted, and saturation increased back to normal levels. No evidence of extrinsic compression was found on chest X-rays or computed tomography scans.

Conclusion

Cases of unknown expiratory central airway collapse reported in the literature were usually managed with positive pressure ventilation. This approach has been unsuccessful in the case described herein. Our hypothesis is that mechanical bending of the left main bronchus occurred due to loss of the patient’s natural position and thoracic muscle tone under general anaesthesia with neuromuscular blockade. When possible, spontaneous ventilation should be maintained in patients with known or suspected ECAC.

Physiotherapy for large airway collapse: an ABC approach

Large airway collapse (LAC) describes the phenomenon of excessive, abnormal, inward movement of the large airways (i.e. trachea and/or main bronchi and/or bronchus intermedius) occurring during the expiratory phase of the respiratory cycle. It is an increasingly well-recognised problem and a prevalent comorbidity in other chronic respiratory conditions (e.g. COPD and asthma). LAC is associated with pervasive respiratory features such as a barking cough, exertional dyspnoea and an increased propensity to lower respiratory tract infection. These symptoms are unpleasant, and patients are often limited in their daily life and their function. The pathophysiology of this condition impairs airway clearance and can cause breathlessness and exercise intolerance, due to a loss of airway patency during expiratory flow. Dysfunctional adaptations to breathing and coughing may further amplify symptoms. This article provides, for the first time, clinically focused physiotherapeutic intervention advice based on our understanding of the pathophysiology of LAC, to support conservative management. It uses the available evidence from LAC, transferable evidence from other conditions and knowledge based on clinical experience. It proposes a practical "ABC model" to ensure physiotherapy assessment and treatments are centred around optimising three key clinical areas: Airways, including airway clearance and cough; Breathing, including breathlessness and breathing pattern; and Capacity for exercise, including an assessment of functional exercise ability.

Thoracic Computed Tomography Scan and Bronchoscopy Appearance of Mounier-Kuhn Syndrome: A Case Report

Mounier-Kuhn syndrome (MKS) is a rare congenital disease with an autosomal recessive inheritance pattern, characterized by an enlargement of the trachea and bronchi. MKS is secondary to a thinning of the muscular mucosa and atrophy of the longitudinal muscle and elastic fibers of the tracheobronchial tree. As a consequence, tracheal diverticulosis and dilatations in the posterior membranous wall appear, along with bronchiectasis that tend to be cystic in appearance. Overall, there is an impairment of mucocilliary clearance, with an ineffective cough, which predisposes the patient to recurrent lower respiratory tract infections. Clinical manifestations vary from asymptomatic to respiratory failure and death, most patients being diagnosed between the third and fourth decades of life. It is an often undiagnosed disease, with a diagnostic algorithm that includes the use of radiological techniques, alone or in combination with bronchoscopy. Specific diagnostic criteria have been developed, based on patients’ tracheal and main bronchi diameter on chest X-ray and thoracic computed tomography scan. We present the case of a 45-year-old African American man who presented with a history of multiples episodes of pneumonia that required management in the intensive care unit, on whom MKS was diagnosed.

Bronchoscopy for Chronic Unexplained Cough: Use of Biopsies and Cultures Increase Diagnostic Yield

BACKGROUND

Prior studies assessing the diagnostic utility of bronchoscopy for chronic unexplained cough have focused primarily on identifying endobronchial anomalies to determine chronic cough etiology. On the basis of our institutional experience, expanding bronchoscopy to include cultures and biopsies can considerably increase its diagnostic yield for identifying the etiology of chronic unexplained cough.

MATERIALS AND METHODS

This retrospective review analyzed bronchoscopies conducted in our institution between 2013 and 2017. Eligibility criteria were bronchoscopies conducted for chronic unexplained cough for which no etiology had been identified before the bronchoscopy. Microbiology, pathology, and cytology results from bronchoscopy were reviewed to identify the etiology of the cough.

RESULTS

Over the study period, 169 bronchoscopies met the eligibility criteria. The average patient age at bronchoscopy was 59.7±14.8 years; 61% were female individuals. Direct visualization identified anatomic etiologies in 48 (28%) patients, most commonly tracheobronchomalacia, and less common conditions, such as tracheobronchopathia osteochondroplastica. Microbiology cultures were positive in 33 (20%) patients, principally Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and nontuberculosis mycobacterium. Pathology results from endobronchial biopsies identified respiratory conditions associated with cough, primarily eosinophilic bronchitis (n=15), as well as neurofibromatosis (n=1) and amyloidosis (n=1). Cytology results did not reveal alternate diagnoses not previously identified.

CONCLUSION

Inclusion of bronchial washings and endobronchial biopsies during bronchoscopy for chronic unexplained cough increased diagnostic yield from 28%, attributable to directly visualized anatomic etiologies, to 41%. The addition of microbiology cultures and pathology analysis significantly increased the diagnostic yield of bronchoscopy in identifying the potential etiology of chronic heretofore unexplained cough.

First series of minimally invasive, robot-assisted tracheobronchoplasty with mesh for severe tracheobronchomalacia

OBJECTIVE

Tracheobronchomalacia is a progressive, debilitating disease with limited treatment options. Open tracheobronchoplasty (TBP) is an accepted surgical option for management of severe tracheobronchomalacia. This study examined the outcomes of the first reported series of robot-assisted TBP (R-TBP).

METHODS

We retrospectively reviewed the records of patients with clinical suspicion for tracheobronchomalacia who had dynamic computed tomography scan and subsequent R-TBP from May 2016 to December 2017.

RESULTS

Four hundred thirty-five patients underwent dynamic computed tomography scan for suspicion of tracheobronchomalacia. Of this group, 42 patients underwent R-TBP. In the surgery group, the median age was 66 years (interquartile range, 39-72 years) and there were 30 women (71%). Respiratory comorbidities included asthma (88%) and chronic obstructive pulmonary disease (52%). The median operative time was 249 minutes (interquartile range, 266-277 minutes). Median hospital length of stay was 3 days (interquartile range, 2-4.75 days), and there were 19 postoperative complications (11 minor and 8 major). There were no mortalities at 90 days. Comparison of preoperative and postoperative pulmonary function testing demonstrated improvement in forced expiratory volume at 1 second by 13.5% (P = .01), forced vital capacity by 14.5% (P < .0001), and peak expiratory flow rate by 21.0% (P < .0001). Quality of life questionnaires also showed improvement with 82% reporting overall satisfaction with the procedure.

CONCLUSIONS

R-TBP can be performed with low morbidity and mortality. Early follow-up reveals significant improvement in pulmonary function testing and high patient satisfaction when compared with preoperative baseline. Long-term follow-up is needed to demonstrate the durability of R-TBP and substantiate its role in the management of patients with symptomatic, severe tracheobronchomalacia.

Improving Quality of Dynamic Airway Computed Tomography Using an Expiratory Airflow Indicator Device

PURPOSE

Dynamic computed tomography (CT) of the airways is increasingly used to evaluate patients with suspected expiratory central airway collapse, but current protocols are susceptible to inadequate exhalation caused by variable patient compliance with breathing instructions during the expiratory phase. We developed and tested a low-cost single-use expiratory airflow indicator device that was designed to improve study quality by providing a visual indicator to both patient and operator when adequate expiratory flow was attained.

MATERIALS AND METHODS

A total of 56 patients undergoing dynamic airway CT were evaluated, 35 of whom were scanned before introduction of the indicator device (control group), with the rest comprising the intervention group. Lung volumes and tracheal cross-sectional areas on inspiratory/expiratory phases were computed using automated lung segmentation and quantitative software analysis. Inadequate exhalation was defined as absolute volume change of <500 mL during the expiratory phase.

RESULTS

Fewer patients in the intervention group demonstrated inadequate exhalation. The average change in volume was higher in the intervention group (P=0.004), whereas the average minimum tracheal cross-sectional area was lower (P=0.01).

CONCLUSIONS

The described expiratory airflow indicator device can be used to ensure adequate exhalation during the expiratory phase of dynamic airway CT. A higher frequency of adequate exhalation may improve reliability and sensitivity of dynamic airway CT for diagnosis of expiratory central airway collapse.