Tracheobronchomalacia: Current Concepts and Controversies

Prevalence and Clinical Characteristics of Pediatric Lower Airway Malacia: Case Series from a Tertiary Center in Turkey

Introduction: Lower airway malacia (LAM) is characterized by a reduction in the cross-sectional luminal area during quiet respiration. There is no gold standard diagnostic test; however, flexible fiberoptic bronchoscopy (FFB) is most frequently utilized. The exact prevalence and incidence of LAM are unknown. This study aimed to determine the prevalence rates of pediatric patients diagnosed with LAM, offer a detailed understanding of their demographic and clinical characteristics, and investigate distinctions between two specific types of LAM, namely, tracheomalacia (TM) and bronchomalacia (BM). Materials and Methods: Patients younger than 18 years diagnosed with LAM using FFB were included in this retrospective case series. Demographic and clinical characteristics and comorbid disorders were compared between patients with isolated BM and those with isolated TM or tracheobronchomalacia (TM/TBM). Results: Among 390 patients who underwent FFB, 65 (16.6%) were diagnosed with LAM, 16 (24.6%) with TM, and 56 (86.2%) with BM. The median age at diagnosis was 15 months. Among them, 59 (90.8%) had other comorbidities; gastrointestinal (GI) disorders were the most common (38.5%). The most common indications for bronchoscopy were recurrent/prolonged lower respiratory tract infections (LRTI) or wheezing (43.1%), while the most frequently observed respiratory physical examination finding was stridor (35.4%). Patients with TM/TBM had significantly higher frequencies of premature births, stridor, retraction, and GI disorders. Conclusion: Patients with stridor without typical laryngomalacia features or recurrent or prolonged LRTI should undergo prompt evaluation for LAM. The potential coexistence of GI disorders such as gastroesophageal reflux disease and swallowing dysfunction should also be considered.

Excessive Dynamic Airway Collapse Severity Scoring System: A Call Out for an Overall Severity Determination

BACKGROUND

Severe excessive dynamic airway collapse (EDAC) is defined as airway narrowing due to posterior wall protrusion into the airway lumen, >90%. We aimed to establish an overall severity score to assess severe EDAC and the need for subsequent intervention.

METHODS

A retrospective study of patients who underwent dynamic bronchoscopy for evaluation of expiratory central airway collapse between January 2019 and July 2021. A numerical value was given to each tracheobronchial segmental collapse: 0 points (<70%), 1 point (70% to 79%), 2 points (80% to 89%), and 3 points (>90%) to be added for an overall EDAC severity score per patient. We compared the score among patients who underwent stent trials (severe EDAC) and those who did not. Based on the receiver operating characteristics curve, a cutoff total score to predict severe EDAC was calculated.

RESULTS

One hundred fifty-eight patients were included. Patients were divided into severe (n = 60) and nonsevere (n = 98) EDAC. A cutoff of 9 as the total score had a sensitivity of 94% and a specificity of 74% to predict severe EDAC, based on an area under the curve 0.888 (95% CI: 0.84, 0.93; P < 0.001).

CONCLUSION

Our EDAC Severity Scoring System was able to discern between severe and nonsevere EDAC by an overall score cutoff of 9, with high sensitivity and specificity for predicting severe disease and the need for further intervention, in our institution.

Common Noninfectious Complications Following Lung Transplantation

According to the Scientific Registry of Transplant Recipients, both transplant volume and survival among lung transplant recipients are improving over time. However, the outcomes of lung transplantation remain challenged by multiple thoracic and extrathoracic complications. With improving lung transplant survival, patients experience prolonged exposure to chronic immunosuppressive agents that can lead to multiple infectious and noninfectious complications. This article focuses on most common noninfectious complications with significant clinical impact.

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.

BMP4 and Wnt signaling interact to promote mouse tracheal mesenchyme morphogenesis

Tracheobronchomalacia and complete tracheal rings are congenital malformations of the trachea associated with morbidity and mortality for which the etiology remains poorly understood. Epithelial expression of Wls (a cargo receptor mediating Wnt ligand secretion) by tracheal cells is essential for patterning the embryonic mouse trachea's cartilage and muscle. RNA sequencing indicated that Wls differentially modulated the expression of BMP signaling molecules. We tested whether BMP signaling, induced by epithelial Wnt ligands, mediates cartilage formation. Deletion of Bmp4 from respiratory tract mesenchyme impaired tracheal cartilage formation that was replaced by ectopic smooth muscle, recapitulating the phenotype observed after epithelial deletion of Wls in the embryonic trachea. Ectopic muscle was caused in part by anomalous differentiation and proliferation of smooth muscle progenitors rather than tracheal cartilage progenitors. Mesenchymal deletion of Bmp4 impaired expression of Wnt/β-catenin target genes, including targets of WNT signaling: Notum and Axin2. In vitro, recombinant (r)BMP4 rescued the expression of Notum in Bmp4-deficient tracheal mesenchymal cells and induced Notum promoter activity via SMAD1/5. RNA sequencing of Bmp4-deficient tracheas identified genes essential for chondrogenesis and muscle development coregulated by BMP and WNT signaling. During tracheal morphogenesis, WNT signaling induces Bmp4 in mesenchymal progenitors to promote cartilage differentiation and restrict trachealis muscle. In turn, Bmp4 differentially regulates the expression of Wnt/β-catenin targets to attenuate mesenchymal WNT signaling and to further support chondrogenesis.

Bronchoscopy-Guided Intervention Therapy With Extracorporeal Membrane Oxygenation Support for Relapsing Polychondritis With Severe Tracheobronchomalacia: A Case Report and Literature Review

Relapsing polychondritis is an immune disorder of unknown etiology involving multiple systems that is characterized by persistent inflammation and destruction of cartilage, including the ears, nose, costal, joint, and airways. Airway involvement caused by relapsing polychondritis is common, and tracheobronchomalacia is the most serious complication, which is life-threatening. Currently, the exact mechanism of relapsing polychondritis with tracheobronchomalacia is unknown. Although glucocorticoids and immunosuppressive agents are administered, failures often occur. Currently, bronchoscopy-guided intervention therapy used in tracheobronchomalacia caused by chronic obstructive pulmonary disease or other etiology has gradually increased, but bronchoscopy-guided intervention therapy with extracorporeal membrane oxygenation assist used in tracheobronchomalacia caused by relapsing polychondritis has not been reported. Here, we report a case of relapsing polychondritis with severe tracheobronchomalacia. Although drug therapy was provided and airway stent implantation was performed, the tracheal stenosis was further aggravated. Because conventional anesthesia and mechanical ventilation cannot meet the needs of bronchoscopy-guided intervention therapy or guarantee sufficient safety. The intervention treatment was performed with the support of extracorporeal membrane oxygenation, which was successfully completed without obvious complications. The symptoms were significantly improved, and the patient was discharged uneventfully.

Argon Plasma Coagulation (APC) for the Treatment of Excessive Dynamic Airway Collapse (EDAC): An Animal Pilot Study

BACKGROUND

Surgical stabilization of the airway through tracheobronchoplasty (TBP) is the current treatment modality for patients with severe symptomatic excessive dynamic airway collapse. However, TBP is associated with increased morbidity and mortality. Bronchoscopic treatment of the posterior membrane using argon plasma coagulation (APC) may be a safer alternative to TBP in highly selected patients. This study aimed to evaluate the effect of APC in the tracheobronchial tree of a sheep animal model.

PATIENTS AND METHODS

Two adult sheep were used for this study. Under flexible bronchoscopy, the posterior tracheal membrane was treated with precise APC using different power settings. Chest computed tomography was done at 2 days and bronchoscopy was performed at 30 days following initial procedure, before euthanasia. The airways were assessed for the presence of treatment-related histopathologic changes along with expression of genes associated with fibrosis.

RESULTS

There was no perioperative or postoperative morbidity or mortality. Chest computed tomography showed no signs of pneumomediastinum or pneumothorax. Flexible bronchoscopy showed adequate tracheobronchial tissue healing process, independent of the power settings used. Histologic changes demonstrated an increased extent of fibroblastic collagen deposition in the treated posterior membrane when higher power settings were used. In a similar manner, APC treatment managed to activate fibrosis-associated gene transcription factors, with higher settings achieving a higher level of expression.

CONCLUSION

APC at high-power settings achieved higher levels of fibroblast collagen deposition at the posterior membrane and higher expression of fibrosis-associated gene transcription factors, when compared with lower settings.

Imaging Course of Lung Transplantation: From Patient Selection to Postoperative Complications

Lung transplant is increasingly performed for the treatment of end-stage lung disease. As the number of lung transplants and transplant centers continues to rise, radiologists will more frequently participate in the care of patients undergoing lung transplant, both before and after transplant. Potential donors and recipients undergo chest radiography and CT as part of their pretransplant assessment to evaluate for contraindications to transplant and to aid in surgical planning. After transplant, recipients undergo imaging during the postoperative hospitalization and also in the long-term outpatient setting. Radiologists encounter a wide variety of conditions leading to end-stage lung disease and a myriad of posttransplant complications, some of which are unique to lung transplantation. Familiarity with these pathologic conditions, including their imaging findings and their temporal relationship to the transplant, is crucial to accurate radiologic interpretation. Knowledge of the surgical techniques and expected postoperative appearance prevents confusing normal posttransplant imaging findings with complications. A basic understanding of the indications, contraindications, and surgical considerations of lung transplant aids in imaging interpretation and protocoling and also facilitates communication between radiologists and transplant physicians. Despite medical and surgical advances over the past several decades, lung transplant recipients currently have an average posttransplant life expectancy of only 6.7 years. As members of the transplant team, radiologists can help maximize patient survival and hopefully increase posttransplant life expectancy and quality of life in the coming decades. ^©RSNA, 2021 An invited commentary by Bierhals is available online. Online supplemental material is available for this article.

Thermoablative Techniques for Excessive Central Airway Collapse: An Ex Vivo Pilot Study on Sheep Tracheal Tissue

BACKGROUND

Tracheobronchoplasty is the definitive treatment for patients with symptomatic excessive central airway collapse. This procedure is associated with high morbidity and mortality rates. Bronchoscopic techniques are an appealing alternative with less morbidity and the ability to apply it in nonsurgical patients. Although thermoablative methods have been proposed as treatment options to induce fibrosis of the posterior tracheobronchial wall, no studies have compared direct histologic effects of such methods. This study compared the effects of electrocautery, radiofrequency ablation, potassium titanyl phosphate laser, and argon plasma coagulation (APC) in the tracheobronchial tree in an ex vivo animal model.

METHODS

Four adult sheep cadavers were used for this study. Under flexible bronchoscopy, the posterior tracheal membrane was treated using different power settings on 4 devices. The airways were assessed for the presence of treatment-related histopathologic changes.

RESULTS

Histologic changes observed were that of acute thermal injury including: surface epithelium ablation, collagen fiber condensation, smooth muscle cytoplasm condensation, and chondrocyte pyknosis. No distinct histologic differences in the treated areas among different modalities and treatment effects were observed. APC at higher power settings was the only modality that produced consistent and homogenous thermal injury effects across all tissue layers with no evidence of complete erosion.

CONCLUSION

Although electrocautery, radiofrequency ablation, potassium titanyl phosphate laser, and APC all induce thermal injury of the airway wall, only APC at high power settings achieves this effect without complete tissue erosion, favoring potential regeneration and fibrosis. Live animal studies are now plausible.

Risk Factors for Tracheobronchomalacia in Preterm Infants With Bronchopulmonary Dysplasia

Aim: To identify the risk factors associated with the development of tracheobronchomalacia (TBM) in preterm infants with bronchopulmonary dysplasia (BPD). Methods: This was a retrospective cohort study using chart reviews of preterm infants born at ≤ 36 week's gestation who underwent flexible fiberoptic bronchoscopy in a tertiary pediatric referral center between January 2015 and January 2020. Indications for the bronchoscopy examination included lobar atelectasis on plain chest film, persistent CO₂ retention, recurrent extubation failure, or abnormal breathing sounds such as wheeze or stridor. Optimal cutoff values for each risk factor were also determined. Results: Fifty-eight preterm infants with BPD were enrolled, of whom 29 (50%) had TBM. There were no significant differences in gestational age and birth weight between those with and without TBM. Significantly more of the patients with TBM had severe BPD compared to those without TBM (68.9 vs. 20.6%, p < 0.001). Clinical parameters that were significantly different between the two groups were included in multivariate analysis. Among these factors, severe BPD was the most powerful risk factor for the development of TBM (odds ratio 5.57, 95% confidence interval 1.32-23.5, p = 0.019). The areas under the receiver operating characteristic curves for peak inspiratory pressure (PIP) and the duration of intubation were 0.788 and 0.75, respectively. The best predictive cutoff values of PIP and duration of intubation for TBM were 18.5 mmHg and 82 days, respectively. Conclusion: Preterm infants with severe BPD are at high risk for the development of TBM, and the risk is even higher in those who receive a higher PIP or are intubated for longer. Bronchoscopy examinations should be considered for the early diagnosis and management of TBM in infants with these risk factors.

Central Airway Collapse, an Underappreciated Cause of Respiratory Morbidity

Dyspnea, cough, sputum production, and recurrent respiratory infections are frequently encountered clinical concerns leading patients to seek medical care. It is not unusual for a well-defined etiology to remain elusive or for the therapeutics of a presumed etiology to be incompletely effective. Either scenario should prompt consideration of central airway pathology as a contributor to clinical manifestations. Over the past decade, recognition of dynamic central airway collapse during respiration associated with multiple respiratory symptoms has become more commonly appreciated. Expiratory central airway collapse may represent the answer to this diagnostic void. Expiratory central airway collapse is an underdiagnosed disorder that can coexist with and mimic asthma, chronic obstructive pulmonary disease, and bronchiectasis. Awareness of expiratory central airway collapse and its spectrum of symptoms is paramount to its recognition. This review includes clear definitions, diagnostics, and therapeutics for this challenging condition. We performed a narrative review through the PubMed (MEDLINE) database using the following MeSH terms: airway collapse, tracheobronchomalacia, tracheomalacia, and bronchomalacia. We include reports from systematic reviews, narrative reviews, clinical trials, and observational studies from 2005 to 2020. Two reviewers evaluated potential references. No systematic reviews were found. A total of 28 references were included into our review. Included studies report experience in the diagnosis and/or treatment of dynamic central airway collapse; case reports and non-English or non-Spanish studies were excluded. We describe the current diagnostic dilemma, highlighting the role of dynamic bronchoscopy and tracheobronchial stent trial; outline the complex therapeutic options (eg, tracheobronchoplasty); and present future directions and challenges.

Interventional Therapies for Central Airways

Central airway obstruction (CAO) is a dangerous and increasingly common problem. CAO refers to lesions causing narrowing of the trachea or mainstem bronchi and is generally divided into malignant and nonmalignant categories. These 2 entities may be caused by a variety of thoracic and extrathoracic diseases. Imaging is critical during the initial assessment of CAO and may help thoracic physicians focus the differential diagnosis and plan the safest and most appropriate diagnostic and therapeutic interventions. However, direct visualization via flexible or rigid bronchoscopy is often necessary for diagnostic and treatment purposes. A large number of procedures can be performed through bronchoscopy, with the goal of relieving the obstruction and improving patency of the airway. Deciding which procedure to perform is based both upon the type of lesion and whether the lesion is due to a malignant or nonmalignant process. Possible interventions include mechanical debridement, laser therapy, argon plasma coagulation, electrocautery, brachytherapy, and stent placement. Immediate postoperative and follow-up imaging is crucial to monitor for immediate, subacute, and chronic complications as well as disease progression and recurrence.

Longitudinal Follow-up of Patients With Tracheobronchomalacia After Undergoing Tracheobronchoplasty: Computed Tomography Findings and Clinical Correlation

PURPOSE

The purpose of this study was to evaluate intermediate and long-term changes in expiratory tracheal collapsibility by computed tomography (CT) in patients with tracheobronchomalacia following surgical treatment with tracheobronchoplasty and to correlate CT findings with clinical findings.

MATERIALS AND METHODS

Between 2003 and 2016, 18 patients with tracheobronchomalacia underwent tracheobronchoplasty and were imaged preoperatively and postoperatively at both intermediate and long-term intervals. Imaging included end-inspiratory and dynamic expiratory phase scans. The cross-sectional area of the airway lumen was measured at 2 standard levels (1 cm above the aortic arch and carina). These measurements were used to calculate % collapsibility. Clinical findings recorded included a questionnaire on symptomatology and a 6-minute walk test.

RESULTS

Before surgery, expiratory collapsibility of the upper trachea was 72%±25% (mean±SD) and that of the lower trachea was 68%±22%. On intermediate follow-up (mean, 1.5 y), collapsibility significantly decreased to 37%±21% at the upper trachea and 35%±19% at the lower trachea (P<0.001). On long-term follow-up (mean, 6 y), collapsibility increased to 51%±20% at the upper trachea and 47%±17% at the lower trachea and was significantly worse than on intermediate follow-up (P=0.002). However, collapsibility on long-term follow-up remained significantly lower than preoperative collapsibility (P=0.015). Clinical findings showed a similar trend as quantitative CT measurements.

CONCLUSION

Expiratory tracheal collapsibility substantially decreases after tracheobronchoplasty on intermediate follow-up. At long-term follow-up, tracheal collapsibility shows a modest increase, but remains significantly lower than the preoperative baseline. Quantitative measurements from dynamic CT have the potential to play an important role as imaging biomarkers for assessing response to tracheobronchoplasty.

The Prevalence of Gastroesophageal Reflux in Patients With Excessive Central Airway Collapse

BACKGROUND

Gastroesophageal reflux (GER) is increasingly recognized as an exacerbating or causal factor in several respiratory diseases. There is a high prevalence of GER in infants with airway malacia. However, such data are lacking in adults.

METHODS

This retrospective study was conducted to determine the relationship between GER and excessive central airway collapse (ECAC). The study included consecutive patients with ECAC referred to the Complex Airway Center at Beth Israel Deaconess Medical Center who underwent esophageal pH testing for GER between July 2014 and June 2018.

RESULTS

Sixty-three of 139 patients with ECAC (45.3%) had documented GER as shown by an abnormal esophageal pH test result. The mean DeMeester score was 32.2, with a symptom association probability of 39.7% of GER-positive patients. Twenty-nine of 63 patients (46%) with GER reported improvement in respiratory symptoms following maximal medical therapy or antireflux surgery without requiring further treatment for ECAC.

CONCLUSIONS

GER is prevalent among patients with ECAC, and aggressive reflux treatment should be considered in these patients prior to considering invasive airway procedures or surgery.

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.

Applications and challenges of using 3D printed implants for the treatment of birth defects

Pediatric implants are a special subclass of a vast number of clinically used medical implants, uniquely designed to address the needs of young patients who are at the onset of their developmental growth stage. Given the vulnerability of the implant receiver, it is crucial that the implants manufactured for small children with birth-associated defects be given careful considerations and great attention to design detail to avoid postoperative complications. In this review, we focus on the most common types of medical implants manufactured for the treatment of birth defects originating from both genetic and environmental causes. Particular emphasis is devoted toward identifying the implant material of choice and manufacturing approaches for the fabrication of pediatric prostheses. Along this line, the emerging role of 3D printing to enable customized implants for infants with congenital disorders is presented, as well as the possible complications associated with prosthetic-related infections that is prevalent in using artificial implants for the treatment of birth malformations.

Tracheobronchial stenting for airway malacia

Tracheobronchomalacia is a rare but clinically troublesome condition in paediatrics. The softening of the major airways - which can include some or all of the tracheobronchial tree can lead to symptoms ranging from the minor (harsh barking cough, recurrent chest infections) to severe respiratory difficulties including prolonged ventilator support and 'near death attacks'. The causes are broadly divided into intrinsic softening of the airway wall which is considered a primary defect (e.g. syndromes; post tracheo-oesophageal fistula repair; extreme prematurity) or secondary malacia due to external compression from vascular structures or cardiac components. These secondary changes can persist even when the external compression is relieved, for example, following the repair of a pulmonary artery sling or double aortic arch. For children with severe clinical symptoms attributed to malacia, consideration is given to possible surgical remedies such as an aortopexy for short limited areas of malacia, or long term positive pressure support with CPAP either by non invasive or tracheostomy interface. More recently the role of stenting in children is receiving attention, especially with the development of newer techniques such as bioabsorbable stents which buy time for a natural history of improvement in the malacia to occur. This paper reviews the stents available and discusses the pros and cons of stenting in paediatric airway malacia.

Airway stenting in excessive central airway collapse

In tracheobronchomalacia (TBM) and other disorders, weakened airway walls lead to expiratory central airway collapse (ECAC) and can cause symptoms of cough, dyspnea, retained secretions, and recurrent pulmonary infections. Diagnosis of severe ECAC is based on the presence of >90% expiratory airway collapse on dynamic computed tomography (CT) and/or bronchoscopy. We offer patients with severe ECAC a trial of airway stenting to determine whether splinting of the central airways leads to improvements in symptoms, quality of life, exercise capacity, or respiratory function. Patients who respond positively to airway stenting are considered for tracheobronchoplasty.

Central airway pathology: clinic features, CT findings with pathologic and virtual endoscopy correlation

Objectives

To describe the imaging features of the central airway pathology, correlating the findings with those in pathology and virtual endoscopy. To propose a schematic and practical approach to reach diagnoses, placing strong emphasis on multidetector computed tomography (MDCT) findings.

Methods

We reviewed our thoracic pathology database and the central airway pathology-related literature. Best cases were selected to illustrate the main features of each disease. MDCT was performed in all cases. Multiplanar and volume-rendering reconstructions were obtained when necessary. Virtual endoscopy was obtained from the CT with dedicated software.

Results

Pathological conditions affecting the central airways are a heterogeneous group of diseases. Focal alterations include benign neoplasms, malignant neoplasms, and non-neoplastic conditions. Diffuse abnormalities are divided into those that produce dilation and those that produce stenosis and tracheobronchomalacia. Direct bronchoscopy (DB) visualises the mucosal layer and is an important diagnostic and therapeutic weapon. However, assessing the deep layers or the adjacent tissue is not possible. MDCT and post-processing techniques such as virtual bronchoscopy (VB) provide an excellent evaluation of the airway wall.

Conclusion

This review presents the complete spectrum of the central airway pathology with its clinical, pathological and radiological features.

Teaching points

• Dividing diseases into diffuse and focal lesions helps narrow the differential diagnosis.

• Focal lesions with nodularity are more likely to correspond to tumours.

• Focal lesions with stenosis are more likely to correspond to inflammatory disease.

• Posterior wall involvement is the main feature in diffuse lesions with stenosis.

Awareness, Competencies, and Practice Patterns in Tracheobronchomalacia: A Survey of Pulmonologists

BACKGROUND

Tracheobronchomalacia (TBM) is a disorder of expiratory central airway collapse. TBM is separate from excessive dynamic airway collapse. Historically TBM has lacked a universally accepted definition. No consensus recommendations on evaluation and management exist. We suspect these unresolved issues contribute to deficits in pulmonologists' awareness and management of TBM.

METHODS

We created a 20-question survey obtaining information about overall awareness, knowledge base, competencies, and practice patterns in managing TBM. The survey was disseminated via email by American College of Chest Physicians to members of their Interventional Chest Diagnostic Procedures Network.

RESULTS

One hundred sixty-five clinicians participated in the survey. Seventy-seven percent of respondents chose the correct definition for TBM. Twenty-two percent of respondents never considered TBM in patients with cough, sputum production, dyspnea, and recurrent infections. Thirty-eight percent did not proceed with further evaluation of TBM if pulmonary function tests were normal. Eighteen percent use a classification system to describe the severity of TBM. Only 29% could identify TBM on bronchoscopy and only 39% identified TBM on computed tomography. Respondents that practice interventional pulmonology demonstrated a better knowledge base of TBM.

CONCLUSION

This survey exposes deficits among pulmonologists in their ability to confidently and correctly diagnose and manage TBM. These deficits are not surprising as our understanding of this clinical entity is evolving. There exists a need for further education of pulmonologists about TBM and a need to promote collaborative efforts through research and expert consensus committees to progress our knowledge and management of this disease.

Spirometer guided chest imaging in children: It is worth the effort!

PURPOSE

Computed tomography (CT) and magnetic resonance imaging (MRI) scans are used to assess and monitor several pediatric lung diseases. It is well recognized that lung volume at the moment of acquisition has a major impact on the appearance of lung parenchyma and airways. Importantly, the sensitivity of chest CT and MRI to detect bronchiectasis and gas trapping is highly dependent on adequate volume control during the image acquisition. This paper describes a feasible method to obtain accurate control of lung volume during chest imaging in pediatric patients with lung disease.

PROCEDURE

A procedure to obtain maximal respiratory manoeuvres with spirometry guidance during image acquisition for CT and MRI is described. This procedure requires training of the subject, an MRI compatible spirometer and close collaboration between a lung function scientist and the radiographer. A good to excellent target volume level for the inspiratory or expiratory scan can be achieved in around 90% of children. An important condition for this success rate is the training of the subject, executed prior to each chest CT or MRI, and instructions by the lung function scientist during the chest CT.

CONCLUSION

Implementing lung volume guidance with a spirometer is an important and feasible step to standardize chest imaging and to optimize the diagnostic yield of chest CT and MRI in children with lung disease. Training and the collaborative effort by a lung function scientist and radiographer is the key factor for success of this procedure. Pediatr Pulmonol. 2017;52:48-56. © 2016 Wiley Periodicals, Inc.

Current concepts in severe adult tracheobronchomalacia: evaluation and treatment

There is increasing recognition of tracheobronchomalacia (TBM) in patients with respiratory complaints, though its true incidence in the adult population remains unknown. Most of these patients have an acquired form of severe diffuse TBM of unclear etiology. The mainstays of diagnosis are dynamic (inspiratory and expiratory) airway computed tomography (CT) scan and dynamic flexible bronchoscopy with forced expiratory maneuvers. While the prevailing definition of TBM is 50% reduction in cross-sectional area, a high proportion of healthy volunteers meet this threshold, thus this threshold fails to identify patients that might benefit from intervention. Therefore, we consider complete or near-complete collapse (>90% reduction in cross-sectional area) of the airway to be severe enough to warrant potential intervention. Surgical central airway stabilization by posterior mesh splinting (tracheobronchoplasty) effectively corrects malacic airways and has been shown to lead to significant improvement in symptoms, health-related quality of life, as well as functional and exercise capacity in carefully selected adults with severe diffuse TBM. A short-term stent trial clarifies a patient's candidacy for surgical intervention. Coordination of care between experienced interventional pulmonologists, radiologists, and thoracic surgeons is essential for optimal outcomes.

Beyond bronchitis: a review of the congenital and acquired abnormalities of the bronchus

Anomalies of the bronchus can be both congenital and acquired. Several different congenital aberrations of the bronchial anatomy are commonly encountered including tracheal bronchus, accessory cardiac bronchus, and bronchial agenesis/aplasia/hypoplasia. In addition, Williams-Campbell syndrome and cystic fibrosis are two other congenital conditions that result in bronchial pathology. Acquired pathology affecting the bronchi can typically be divided into three broad categories of bronchial disease: bronchial wall thickening, dilatation/bronchiectasis, and obstruction/stenosis. Bronchial wall thickening is the common final response of the airways to irritants, which cause the bronchi to become swollen and inflamed. Bronchiectasis/bronchial dilatation can develop in response to many aetiologies, including acquired conditions such as infection, pulmonary fibrosis, recurrent or chronic aspiration, as well as because of congenital conditions such as cystic fibrosis. The causes of obstruction and stenosis are varied and include foreign body aspiration, acute aspiration, tracheobronchomalacia, excessive dynamic airway collapse, neoplasm, granulomatous disease, broncholithiasis, and asthma. Knowledge of normal bronchial anatomy and its congenital variants is essential for any practicing radiologist. It is the role of the radiologist to identify common imaging patterns associated with the various categories of bronchial disease and provide the ordering clinician a useful differential diagnosis tailored to the patient’s clinical history and imaging findings.

Teaching Points

• Bronchial disorders are both congenital and acquired in aetiology.

• Bronchial disease can be divided by imaging appearance: wall thickening, dilatation, or obstruction.

• Bronchial wall thickening is the common final response of the airways to irritants.

• Imaging patterns must be recognised and the differential diagnosis tailored for patient management.

Tracheobronchomalacia diagnosed by tracheobronchography in ventilator-dependent infants

BACKGROUND

Tracheobronchomalacia prevalence in premature infants on prolonged mechanical ventilation is high.

OBJECTIVE

To examine the prevalence of tracheobronchomalacia diagnosed by tracheobronchography in ventilator-dependent infants, and describe the demographic, clinical and dynamic airway characteristics of those infants with tracheobronchomalacia.

MATERIALS AND METHODS

This retrospective review studies 198 tracheobronchograms performed from 1998 to 2011 in a cohort of 158 ventilator-dependent infants <2 years of age. Dynamic airway assessment during tracheobronchography determined the optimal positive end-expiratory pressure to maintain airway patency at expiration in those infants with tracheobronchomalacia.

RESULTS

Tracheobronchograms were performed at a median age of 52 weeks post menstrual age. The primary diagnoses in these infants were bronchopulmonary dysplasia (53%), other causes of chronic lung disease of infancy (28%) and upper airway anomaly (13%). Of those with bronchopulmonary dysplasia, 48% had tracheobronchomalacia. Prematurity (P=0.01) and higher baseline - pre-tracheobronchogram positive end-expiratory pressure (P=0.04) were significantly associated with tracheobronchomalacia. Dynamic airway collapse during tracheobronchography showed statistically significant airway opening at optimal positive end-expiratory pressure (P < 0.001). There were no significant complications noted during and immediately following tracheobronchography.

CONCLUSION

The overall prevalence of tracheobronchomalacia in this cohort of ventilator-dependent infants is 40% and in those with bronchopulmonary dysplasia is 48%. Infants born prematurely and requiring high pre-tracheobronchogram positive end-expiratory pressure were likely to have tracheobronchomalacia. Tracheobronchography can be used to safely assess the dynamic function of the airway and can provide the clinician the optimal positive end-expiratory pressure to maintain airway patency.

Laser tracheobronchoplasty: a novel technique for the treatment of symptomatic tracheobronchomalacia

The management of tracheobronchomalacia is a very challenging problem with few treatment options. This study aims to evaluate the outcomes of a novel surgical treatment for membranous tracheobronchomalacia. A consecutive series of patients with tracheobronchomalacia were treated with two to three holmium laser scarring surgeries of the hyperdynamic tracheal and bronchial walls for the purpose of stiffening them through fibrosis. Patients filled out a Dyspnea Index questionnaire before and after treatment. Ten patients were treated for their tracheobronchomalacia with a mean age of 54 years. Symptoms included severe dyspnea, dry cough, recurrent pulmonary infections, and respiratory failure. Fifty percent of patients presented with wheezing refractory to traditional treatment. Tracheobronchomalacia was associated with gastroesophageal reflux disease (n = 8), obstructive sleep apnea (n = 5), and tracheal stenosis (n = 3). Only 50 % of patients presented with morbid obesity. All cases showed significant improvement of their respiratory symptoms with a mean postoperative difference of 22.3 out of a maximum impairment score of 40 (P < 0.01) on the Dyspnea Index. The mean number of procedures was 2.3 per patient with the average laser energy delivered per procedure of 1600 J. Laser tracheobronchoplasty is a safe, easy to adopt, and effective technique for the treatment of membranous tracheobronchomalacia. It presents a simple alternative to the commonly used procedures like endoluminal stenting and open tracheobronchoplasty.

Imaging of Diseases of the Large Airways

Imaging of the large airways is key to the diagnosis and management of a wide variety of congenital, infectious, malignant, and inflammatory diseases. Involvement can be focal, regional, or diffuse, and abnormalities can take the form of masses, thickening, narrowing, enlargement, or a combination of patterns. Recognition of the typical morphologies, locations, and distributions of large airways disease is central to an accurate imaging differential diagnosis.

Surgical Treatment of Tracheobronchomalacia: A novel approach

Tracheobronchomalacia, as a whole, is likely misdiagnosed and underestimated as a cause of respiratory compromise in pediatric patients. Currently, there is no standardized approach for the overall evaluation of pediatric tracheobronchomalacia (TBM) and the concept of excessive dynamic airway collapse (EDAC); no grading score for the evaluation of severity; nor a standardized means to successfully approach TBM and EDAC. This paper describes our experience standardizing the approach to these complex patients whose backgrounds include different disease etiologies, as well as a variety of comorbid conditions. Preoperative and postoperative evaluation of patients with severe TBM and EDAC, as well as concurrent development of a prospective grading scale, has allowed us to ascertain correlation between surgery, symptoms, and effectiveness on particular tracheal-bronchial segments. Long-term, continued collection of patient characteristics, surgical technique, complications, and outcomes must be collected given the overall heterogeneity of this particular population.

Imaging of Large Airways Disorders

OBJECTIVE

Recent technical advances, including the routine use of CT thin sections and techniques such as 2D minimum-intensity-projection and 3D volume images, have increased our ability to detect large airways diseases. Furthermore, dedicated CT protocols allow the evaluation of dynamic airway dysfunction.

CONCLUSION

With diseases of the large airways more commonly seen in daily practice, it is important that radiologists be familiar with the appearances, differential diagnosis, and clinical implications of these entities.

Approach to chest computed tomography

Computed tomography (CT) is central to the detection and diagnosis of a wide variety of pulmonary, cardiovascular, and other diseases of the chest. Successful interpretation of thoracic CT requires both an appreciation of the spectrum of normal appearances of the chest and a systematic approach to the characterization of thoracic pathology. This article provides an introduction to basic CT techniques and protocols, a review of normal CT anatomy, and an overview of commonly encountered abnormalities.

[Tracheobronchial prosthesis in Mounier-Kuhn syndrome: New perspectives]

INTRODUCTION

Mounier-Kuhn syndrome or tracheobronchomegaly is a rare congenital condition, the management of which is complex. We report the case of a patient who was treated with interventional endoscopy.

OBSERVATION

We describe the case of a 74-year-old man with a diagnosis of tracheobronchomegaly who was admitted in 2003 with a background of deteriorating respiratory status and the occurrence of postural syncope. He initially received a tracheobronchial silicone Y prosthesis, extended with metal prostheses at the tracheal and bronchial level. This arrangement remained stable until 2011. He then began to develop episodes of asphyxia related to posterior dislocation of the tracheobronchial prosthesis, after breakage of the metallic mesh tracheal prosthesis. A new tracheobronchial prosthesis Y was then placed, custom-made from a 3D model of the airways. This was clinically and functionally effective.

DISCUSSION

This case describes the management of a patient with Mounier-Kuhn syndrome by interventional bronchoscopy, with the adaptation of prosthetic materials, on an individual basis, to the anatomy of the patient's airway.

Treatment of severe porcine tracheomalacia with a 3-dimensionally printed, bioresorbable, external airway splint

IMPORTANCE

The study demonstrates use of a novel intervention for severe tracheobronchomalacia (TBM).

OBJECTIVE

To test a novel, 3-dimensionally (3D) printed, bioresorbable airway splint for efficacy in extending survival in a porcine model of severe, life-threatening TBM.

DESIGN AND PARTICIPANTS

A randomized, prospective animal trial was used to evaluate an external airway splint as treatment of severe, life-threatening TBM in a multi-institutional, multidisciplinary collaboration between a biomedical engineering department and an academic animal surgery center. Six 2-month-old Yorkshire pigs underwent tracheal cartilage division and inner tracheal lumen dissociation and were randomly assigned to splint treatment (n = 3) or control groups (n = 3). Two additional pigs had the splint placed over their normal trachea.

INTERVENTIONS

A 3D-printed, bioresorbable airway splint was assessed in a porcine animal model of life-threatening TBM. The open-cylindrical, bellow-shaped, porous polycaprolactone splint was placed externally and designed to suspend the underlying collapsed airway. Two additional animals were splinted without model creation.

MAIN OUTCOMES AND MEASURES

The observer-based Westley Clinical Croup Scale was used to assess the clinical condition of animals postoperatively. Animal survival time was noted.

RESULTS

Complete or nearly complete tracheal lumen collapse was observed in each animal, with resolution of symptoms in all of the experimental animals after splint placement. Using our severe TBM animal model, survival was significantly longer in the experimental group receiving the airway splint after model creation than in the control group (P = .0495).

CONCLUSIONS AND RELEVANCE

A multidisciplinary effort producing a computer-aided designed, computer-aided manufactured bioresorbable tracheobronchial splint was tested in a porcine model of severe TBM and was found to extend survival time. Mortality in the splinted group was ascribed to the TBM model based on the lack of respiratory distress in splinted pigs, long-term survival in animals implanted with the splint without TBM, and necropsy findings.

Static end-expiratory and dynamic forced expiratory tracheal collapse in COPD

AIM

To determine the range of tracheal collapse at end-expiration among chronic obstructive pulmonary disease (COPD) patients and to compare the extent of tracheal collapse between static end-expiratory and dynamic forced-expiratory multidetector-row computed tomography (MDCT).

MATERIALS AND METHODS

After institutional review board approval and obtaining informed consent, 67 patients meeting the National Heart, Lung, and Blood Institute (NHLBI)/World Health Organization (WHO) Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria for COPD were sequentially imaged using a 64-detector-row CT machine at end-inspiration, during forced expiration, and at end-expiration. Standardized respiratory coaching and spirometric monitoring were employed. Mean percentage tracheal collapse at end-expiration and forced expiration were compared using correlation analysis, and the power of end-expiratory cross-sectional area to predict excessive forced-expiratory tracheal collapse was computed following construction of receiver operating characteristic (ROC) curves.

RESULTS

Mean percentage expiratory collapse among COPD patients was 17 ± 18% at end-expiration compared to 62 ± 16% during forced expiration. Over the observed range of end-expiratory tracheal collapse (approximately 10-50%), the positive predictive value of end-expiratory collapse to predict excessive (≥80%) forced expiratory tracheal collapse was <0.3.

CONCLUSION

COPD patients demonstrate a wide range of end-expiratory tracheal collapse. The magnitude of static end-expiratory tracheal collapse does not predict excessive dynamic expiratory tracheal collapse.

Advanced large airway CT imaging in children: evolution from axial to 4-D assessment

Continuing advances in multidetector computed tomography (MDCT) technology are revolutionizing the non-invasive evaluation of congenital and acquired large airway disorders in children. For example, the faster scanning time and increased anatomical coverage that are afforded by MDCT are especially beneficial to children. MDCT also provides high-quality multiplanar 2-dimensional (2-D), internal and external volume-rendering 3-dimensional (3-D), and dynamic 4-dimensional (4-D) imaging. These advances have enabled CT to become the primary non-invasive imaging modality of choice for the diagnosis, treatment planning, and follow-up evaluation of various large airway disorders in infants and children. It is thus essential for radiologists to be familiar with safe and effective techniques for performing MDCT and to be able to recognize the characteristic imaging appearances of large airway disorders affecting children.

[Tracheobronchomalacia in adults: breakthroughs and controversies]

Tracheobronchomalacia (TBM) in adults is a disease defined by a reduction of more than 50% of the airway lumen during expiration. It encompasses many etiologies that differ in their morphologic aspects, pathophysiological mechanisms and histopathologies. TBM is encountered with increasing frequency, as it is more easily diagnosed with new imaging techniques and diagnostic bronchoscopy, as well as because of its frequent association with Chronic Obstructive Pulmonary Disease (COPD), which represents the most frequent etiology for acquired TBM in adults. A distinction between TBM in association with failure of the cartilaginous part of the airways and TBM affecting only the posterior membranous part is emerging since their physiopathology and treatment differ. The therapeutic management of TBM should be as conservative as possible. Priority should be given to identification and treatment of associated respiratory diseases, such as asthma or COPD. Surgery addressing extrinsic compression (thyroid goiter or tumor, for example) may be necessary. Noninvasive ventilation can be considered in patients with increasing symptoms. Endoscopic options, such as the placement of stents, should only be used as palliative or temporary solutions, because of the high complication rates. Symptomatic improvement after stenting might be helpful in selecting patients in whom a surgical management with tracheobronchoplasty can be useful.