Dynamic Expiratory Tracheal Collapse in Morbidly Obese COPD Patients

Excessive Dynamic Airway Collapse: Large Airway Function During Exercise

Large airway collapse on expiration is an increasingly recognized cause of airway centric symptoms. The 2 primary conditions are tracheobronchomalacia and excessive dynamic airway collapse, the latter a common comorbidity in those with underlying lung disease. The exertional dyspnea associated with these conditions is complex and exercise intolerance is a key clinical feature, despite the fact that the precise relationship is not fully understood. Forced expiratory maneuvers during supine bronchoscopy or imaging studies are used to evaluate these conditions. However, it may be relevant to characterize large airway function during occasions when patients present their symptoms.

Low-Dose Whole-Chest Dynamic CT for the Assessment of Large Airway Collapsibility in Patients with Suspected Tracheobronchial Instability

Purpose To quantify tracheal collapsibility using low-dose four-dimensional (4D) CT and to compare visual and quantitative 4D CT-based assessments with assessments from paired inspiratory-expiratory CT, bronchoscopy, and spirometry. Materials and Methods The authors retrospectively analyzed 4D CT examinations (January 2016-December 2022) during shallow respiration in 52 patients (mean age, 66 years ± 12 [SD]; 27 female, 25 male), including 32 patients with chronic obstructive pulmonary disease (mean forced expiratory volume in 1 second percentage predicted [FEV1%], 50% ± 27), with suspected tracheal collapse. Paired CT data were available for 27 patients and bronchoscopy data for 46 patients. Images were reviewed by two radiologists in consensus, classifying patients into three groups: 50% or greater tracheal collapsibility, less than 50% collapsibility, or fixed stenosis. Changes in minimal tracheal lumen area, tracheal volume, and lung volume from inspiration to expiration were quantified using YACTA software. Tracheal collapsibility between groups was compared employing one-way analysis of variance (ANOVA). For related samples within one group, ANOVA with repeated measures was used. Spearman rank order correlation coefficient was calculated for collapsibility versus pulmonary function tests. Results At 4D CT, 25 of 52 (48%) patients had tracheal collapsibility of 50% or greater, 20 of 52 (38%) less than 50%, and seven of 52 (13%) had fixed stenosis. Visual assessment of 4D CT detected more patients with collapsibility of 50% or greater than paired CT, and concordance was 41% (P < .001). 4D CT helped identify more patients with tracheal collapsibility of 50% or greater than did bronchoscopy, and concordance was 74% (P = .39). Mean collapsibility of tracheal lumen area and volume at 4D CT were higher for 50% or greater visually assessed collapsibility (area: 53% ± 9 and lumen: 52% ± 10) compared with the less than 50% group (27% ± 9 and 26% ± 6, respectively) (P < .001), whereas both tracheal area and volume were stable for the fixed stenosis group (area: 16% ± 12 and lumen: 21% ± 11). Collapsibility of tracheal lumen area and volume did not correlate with FEV1% (rs = -0.002 to 0.01, P = .99-.96). Conclusion The study demonstrated that 4D CT is feasible and potentially more sensitive than paired CT for central airway collapse. Expectedly, FEV1% was not correlated with severity of tracheal collapsibility. Keywords: CT-Quantitative, Tracheobronchial Tree, Chronic Obstructive Pulmonary Disease, Imaging Postprocessing, Thorax Supplemental material is available for this article. © RSNA, 2024.

Feasibility of continuous bronchoscopy during exercise in the assessment of large airway movement in healthy subjects

Excessive dynamic airway collapse (EDAC) is a recognized cause of exertional dyspnea arising due to invagination of the trachea and/or main bronchi. EDAC is typically assessed by evaluating large airway movement with forced expiratory maneuvers. This differs from the respiratory response to exercise hyperpnea. We aimed to evaluate large airway movement during physical activity, with continuous bronchoscopy during exercise (CBE), in healthy subjects and compare findings with resting bronchoscopic maneuvers and imaging techniques. Twenty-eight individuals were recruited to complete two visits including treadmill-based CBE, to voluntary exhaustion, and cine magnetic resonance imaging (MRI) with forced expiratory maneuvers at rest. Twenty-five subjects [aged 29 (26-33) yr, 52% female] completed the study (n = 2 withdrew before bronchoscopy, and one was unable to tolerate insertion of bronchoscope). The majority (76%) achieved a peak heart rate of >90% predicted during CBE. The procedure was prematurely terminated in five subjects (n = 3; elevated blood pressure and n = 2; minor oxygen desaturation). The CBE assessment enabled adequate tracheal visualization in all cases. Excessive dynamic airway collapse (tracheal collapse ≥50%) was identified in 16 subjects (64%) on MRI, and in six (24%) individuals during resting bronchoscopy, but in no cases with CBE. No serious adverse events were reported, but minor adverse events were evident. The CBE procedure permits visualization of large airway movement during physical activity. In healthy subjects, there was no evidence of EDAC during strenuous exercise, despite evidence during forced maneuvers on imaging, thus challenging conventional approaches to diagnosis.NEW & NOTEWORTHY This study demonstrates that large airway movement can be visualized with bronchoscopy undertaken during vigorous exercise. This approach does not require sedation and permits characterization of the behavior of the large airways and the tendency toward collapse during upright, ambulatory exercise. In healthy individuals, the response pattern of the large airways during exercise appears to differ markedly from the pattern of airway closure witnessed during forced expiratory maneuvers, assessed via imaging.

Fleischner Society: Glossary of Terms for Thoracic Imaging

Members of the Fleischner Society have compiled a glossary of terms for thoracic imaging that replaces previous glossaries published in 1984, 1996, and 2008, respectively. The impetus to update the previous version arose from multiple considerations. These include an awareness that new terms and concepts have emerged, others have become obsolete, and the usage of some terms has either changed or become inconsistent to a degree that warranted a new definition. This latest glossary is focused on terms of clinical importance and on those whose meaning may be perceived as vague or ambiguous. As with previous versions, the aim of the present glossary is to establish standardization of terminology for thoracic radiology and, thereby, to facilitate communications between radiologists and clinicians. Moreover, the present glossary aims to contribute to a more stringent use of terminology, increasingly required for structured reporting and accurate searches in large databases. Compared with the previous version, the number of images (chest radiography and CT) in the current version has substantially increased. The authors hope that this will enhance its educational and practical value. All definitions and images are hyperlinked throughout the text. Click on each figure callout to view corresponding image. © RSNA, 2024 Supplemental material is available for this article. See also the editorials by Bhalla and Powell in this issue.

[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.

Sex matters: the frequently overlooked importance of considering sex in computational models

Personalised medicine and the development of a virtual human or a digital twin comprises visions of the future of medicine. To realise these innovations, an understanding of the biology and physiology of all people are required if we wish to apply these technologies at a population level. Sex differences in health and biology is one aspect that has frequently been overlooked, with young white males being seen as the "average" human being. This has not been helped by the lack of inclusion of female cells and animals in biomedical research and preclinical studies or the historic exclusion, and still low in proportion, of women in clinical trials. However, there are many known differences in health between the sexes across all scales of biology which can manifest in differences in susceptibility to diseases, symptoms in a given disease, and outcomes to a given treatment. Neglecting these important differences in the development of any health technologies could lead to adverse outcomes for both males and females. Here we highlight just some of the sex differences in the cardio-respiratory systems with the goal of raising awareness that these differences exist. We discuss modelling studies that have considered sex differences and touch on how and when to create sex-specific models. Scientific studies should ensure sex differences are included right from the study planning phase and results reported using sex as a biological variable. Computational models must have sex-specific versions to ensure a movement towards personalised medicine is realised.

Tracheobronchoplasty yields long-term anatomy, function, and quality of life improvement for patients with severe excessive central airway collapse

OBJECTIVES

This study examines the long-term anatomic and clinical effects of tracheobronchoplasty in severe excessive central airway collapse.

METHODS

Included patients underwent tracheobronchoplasty for excessive central airway collapse (2002-2016). The cross-sectional area of main airways on dynamic airway computed tomography was measured before and after tracheobronchoplasty. Expiratory collapse was calculated as the difference between inspiratory and expiratory cross-sectional area divided by inspiratory cross-sectional area ×100. The primary outcome was improvement in the percentage of expiratory collapse in years 1, 2, and 5 post-tracheobronchoplasty. Secondary outcomes included mean response profile for the 6-minute walk test, Cough-Specific Quality of Life Questionnaire, Karnofsky Performance Status score, and St George Respiratory Questionnaire. Repeated-measures analysis of variance was used for statistical analyses.

RESULTS

The cohort included 61 patients with complete radiological follow-up at years 1, 2, and 5 post-tracheobronchoplasty. A significant linear decrease in the percentage of expiratory collapsibility of the central airways after tracheobronchoplasty was present. Anatomic repair durability was preserved 5 years after tracheobronchoplasty, with decrease in percentage of expiratory airway collapse up to 40% and 30% at years 1 and 2, respectively. The St George Respiratory Questionnaire (74.7 vs 41.8%, P < .001) and Cough-Specific Quality of Life Questionnaire (78 vs 47, P < .001) demonstrated significant improvement at year 5 compared with baseline. Similar results were observed in the 6-minute walk test (1079 vs 1268 ft, P < .001) and Karnofsky score (57 vs 82, P < .001).

CONCLUSIONS

Tracheobronchoplasty has durable effects on airway anatomy, functional status, and quality of life in carefully selected patients with severe excessive central airway collapse.

Successful step-by-step diagnosis and management of expiratory central airway collapse

A 45-year-old woman with recurrent dyspnea for 40 years was previously diagnosed with bronchial asthma and spasmodic dysphonia. On admission, the patient was diagnosed with expiratory central airway collapse (ECAC) due to expiratory dynamic airway collapse based on radiographic examination, chest computed tomography, and bronchoscopy. After continuous positive airway pressure and temporal airway stenting, surgical tracheobronchoplasty and tracheal membranous portion reinforcement using polypropylene mesh successfully relieved the respiratory symptoms. In patients with airway obstructive disease refractory to conventional therapies, ECAC should be considered.

Postmorterm Computed Tomography and Autopsy to Confirm Sudden Death Due to Tracheal Compression by Mediastinal Fat Tissue in a Young Man With Obesity

A man in his early twenties with obesity was found dead in his apartment. The deceased was found naked and surrounded by empty bottles of electrolytes. An autopsy performed approximately 6 days postmortem and gross inspection revealed the absence of injury and no apparent extrinsic cause of death. It was decided to dissect to investigate the cause of death. The deceased had become morbidly obese (weight, 98 kg; height, 160 cm; body mass index, 38.3). Shortly before his death, he presented at a clinic complaining of gastric discomfort and heartburn, but other than hypertension (155/91 mmHg) no specific abnormality was found. He was normothermic (36.6℃), and his blood oxygen saturation was normal (97%). Postmortem computed tomography of the thorax revealed a mediastinal mass obstructing the trachea, an upper-airway obstruction, and a narrowed thoracic cavity due to upward compression by an enlarged fatty liver. Autopsy confirmed that the tracheal mass was fatty tissue within the thymus and that upward pressure from an enlarged fatty liver had compressed the thoracic cavity. The deceased likely developed nocturnal chronic hypoxia because of compression by the mediastinal fat mass as well as intermittent hypoxia because of obstructive sleep apnea when lying supine. Chronic and intermittent hypoxia, diabetes, and obesity activate the sympathetic nervous system, increasing the risk of hypertension, heart failure, and arrhythmias. Histological findings showed pulmonary congestion and edema, reflecting heart failure as well as myocardial fragmentation and waving, showing hyper-contraction and hyper-relaxation, respectively. Hypertension, feeling overheated, and myocardial hyper-contraction can be explained as sympathetic nerve over-activation. Intra-cardiac coagulation and a renal cortical pallor suggested subacute death from cardiogenic shock due to heart failure. Postmortem computed tomography before autopsy detected airway obstruction and revealed the cause and pathophysiology of unexpected death in a young man with morbid obesity. Therefore, this could be a potentially useful clinical practice for determining the cause of death postmortem.

Semiquantitative Chest Computed Tomography Assessment Identifies Expiratory Central Airway Collapse in Symptomatic Military Personnel Deployed to Iraq and Afghanistan

PURPOSE

We noted incidental findings on chest computed tomography (CT) imaging of expiratory central airway collapse (ECAC) in dyspneic patients after military deployment to southwest Asia (mainly Iraq and Afghanistan). We developed a standardized chest CT protocol with dynamic expiration to enhance diagnostic reliability and investigated demographic, clinical, and deployment characteristics possibly associated with ECAC.

MATERIALS AND METHODS

We calculated ECAC in 62 consecutive post-9/11 deployers with dyspnea who underwent multi-detector chest CT acquisition. ECAC was defined as ≥70% reduction in the cross-sectional tracheal area at dynamic expiration. We compared demographics (age, smoking, body mass index), comorbid conditions (gastroesophageal reflux, obstructive sleep apnea [OSA]), and clinical findings (air trapping, forced expiratory volume in 1 second percent predicted) in deployers with and without ECAC. We examined associations between ECAC and forced expiratory volume in 1 second percent predicted, air trapping, OSA, deployment duration, and blast exposure.

RESULTS

Among 62 consecutive deployers with persistent dyspnea, 37% had ECAC. Three had severe (>85%) collapse. Those with ECAC were older (mean age 46 vs. 40 y, P=0.02), but no other demographic or clinical characteristics were statistically different among the groups. Although not statistically significant, ECAC odds were 1.5 times higher (95% confidence interval: 0.9, 2.5) for each additional year of southwest Asia deployment. Deployers with ECAC had 1.6 times greater odds (95% confidence interval: 0.5, 4.8) of OSA.

CONCLUSIONS

Findings suggest that ECAC is common in symptomatic southwest Asia deployers. Chest high-resolution CT with dynamic expiration may provide an insight into the causes of dyspnea in this population, although risk factors for ECAC remain to be determined. A standardized semiquantitative approach to CT-based assessment of ECAC should improve reliable diagnosis in dyspneic patients.

Detection and diagnosis of large airway collapse: a systematic review

Large airway collapse (LAC) is a frequently encountered clinical problem, caused by tracheobronchomalacia +/− excessive dynamic airway collapse, yet there are currently no universally accepted diagnostic criteria. We systematically reviewed studies reporting a diagnostic approach to LAC in healthy adults and patients, to compare diagnostic modalities and criteria used. Electronic databases were searched for relevant studies between 1989 and 2019. Studies that reported a diagnostic approach using computed tomography (CT), magnetic resonance imaging or flexible fibreoptic bronchoscopy were included. Random effects meta-analyses were performed to estimate the prevalence of LAC in healthy subjects and in patients with chronic obstructive airway diseases. We included 41 studies, describing 10 071 subjects (47% female) with a mean±sd age of 59±9 years. Most studies (n=35) reported CT findings, and only three studies reported bronchoscopic findings. The most reported diagnostic criterion was a ≥50% reduction in tracheal or main bronchi calibre at end-expiration on dynamic expiratory CT. Meta-analyses of relevant studies found that 17% (95% CI: 0–61%) of healthy subjects and 27% (95% CI: 11–46%) of patients with chronic airways disease were classified as having LAC, using this threshold. The most reported approach to diagnose LAC utilises CT diagnostics, and at a threshold used by most clinicians (i.e., ≥50%) may classify a considerable proportion of healthy individuals as being abnormal and having LAC in a quarter of patients with chronic airways disease. Future work should focus on establishing more precise diagnostic criteria for LAC, relating this to relevant physiological and disease sequelae.

CT is mostly used to diagnose LAC, and at a threshold used by most clinicians (i.e. ≥50%) that would classify a large proportion of healthy individuals as being abnormal and LAC in a quarter of patients with chronic airway diseaseshttps://bit.ly/3izAuSk

Central airway collapse is related to obesity independent of asthma phenotype

BACKGROUND AND OBJECTIVE

Late-onset non-allergic asthma in obesity is characterized by an abnormally compliant, collapsible lung periphery; it is not known whether this abnormality exists in proximal airways. We sought to compare collapsibility of central airways between lean and obese individuals with and without asthma.

METHODS

A cross-sectional study comparing luminal area and shape (circularity) of the trachea, left mainstem bronchus, right bronchus intermedius and right inferior lobar bronchus at RV and TLC by CT was conducted.

RESULTS

In 11 lean controls (BMI: 22.4 (21.5, 23.8) kg/m² ), 10 lean individuals with asthma (23.6 (22.0, 24.8) kg/m² ), 10 obese controls (45.5 (40.3, 48.5) kg/m² ) and 21 obese individuals with asthma (39.2 (35.8, 42.9) kg/m² ), lumen area and circularity increased significantly with an increase in lung volume from RV to TLC for all four airways (P < 0.05 for all). Changes in area and circularity with lung volume were similar in obese individuals with and without asthma, and both obese groups had severe airway collapse at RV. In multivariate analysis, change in lumen area was related to BMI and change in circularity to waist circumference, but neither was related to asthma diagnosis.

CONCLUSION

Excessive collapse of the central airways is related to obesity, and occurs in both obese controls and obese asthma. Increased airway collapse could contribute to ventilation abnormalities in obese individuals particularly at lower lung volumes, and complicate asthma in obese individuals.

Effect of BMI on health care expenditures stratified by COPD GOLD severity grades: Results from the LQ-DMP study

Chronic Obstructive Pulmonary Disease (COPD) is characterized by persistent respiratory symptoms and airflow limitation, which is progressive and not fully reversible. In patients with COPD, body mass index (BMI) is an important parameter associated with health outcomes, e.g. mortality and health-related quality of life. However, so far no study evaluated the association of BMI and health care expenditures across different COPD severity grades. We used claims data and documentation data of a Disease Management Program (DMP) from a statutory health insurance fund (AOK Bayern). Patients were excluded if they had less than 4 observations in the 8 years observational period. Generalized additive mixed models with smooth functions were used to evaluate the association between BMI and health care expenditures, stratified by severity of COPD, indicated by GOLD grades 1-4. We included 30,682 patients with overall 188,725 observations. In GOLD grades 1-3 we found an u-shaped relation of BMI and expenditures, where patients with a BMI of 30 or slightly above had the lowest and underweight and obese patients had the highest health care expenditures. Contrarily, in GOLD grade 4 we found an almost linear decline of health care expenditures with increasing BMI. In terms of expenditures, the often reported obesity paradox in patients with COPD was clearly reflected in GOLD grade 4, while in all other severity grades underweight as well as severely obese patients caused the highest health care expenditures. Reduction of obesity may thus reduce health care expenditures in GOLD grades 1-3.

Paratracheal Paraseptal Emphysema and Expiratory Central Airway Collapse in Smokers

RATIONALE

Expiratory central airway collapse is associated with respiratory morbidity independent of underlying lung disease. However, not all smokers develop expiratory central airway collapse, and the etiology of expiratory central airway collapse in adult smokers is unclear. Paraseptal emphysema in the paratracheal location, by untethering airway walls, may predispose smokers to developing expiratory central airway collapse.

OBJECTIVES

To evaluate whether paratracheal paraseptal emphysema is associated with expiratory central airway collapse.

METHODS

We analyzed paired inspiratory and expiratory computed tomography scans from participants enrolled in a multicenter study (Genetic Epidemiology of Chronic Obstructive Pulmonary Disease) of smokers aged 45 to 80 years. Expiratory central airway collapse was defined as greater than or equal to 50% reduction in cross-sectional area of the trachea during expiration. In a nested case-control design, participants with and without expiratory central airway collapse were included in a 1:2 fashion, and inspiratory scans were further analyzed using the Fleischner Society criteria for presence of centrilobular emphysema, paraseptal emphysema, airway wall thickening, and paratracheal paraseptal emphysema (maximal diameter ≥ 0.5 cm).

RESULTS

A total of 1,320 patients were included, 440 with and 880 without expiratory central airway collapse. Those with expiratory central airway collapse were older, had higher body mass index, and were less likely to be men or current smokers. Paratracheal paraseptal emphysema was more frequent in those with expiratory central airway collapse than control subjects (16.6 vs. 11.8%; P = 0.016), and after adjustment for age, race, sex, body mass index, smoking pack-years, and forced expiratory volume in 1 second, paratracheal paraseptal emphysema was independently associated with expiratory central airway collapse (adjusted odds ratio, 1.53; 95% confidence interval, 1.18-1.98; P = 0.001). Furthermore, increasing size of paratracheal paraseptal emphysema (maximal diameter of at least 1 cm and 1.5 cm) was associated with greater odds of expiratory central airway collapse (adjusted odds ratio, 1.63; 95% confidence interval, 1.18-2.25; P = 0.003 and 1.77; 95% confidence interval, 1.19-2.64; P = 0.005, respectively).

CONCLUSIONS

Paraseptal emphysema adjacent to the trachea is associated with expiratory central airway collapse. The identification of this risk factor on inspiratory scans should prompt further evaluation for expiratory central airway collapse. Clinical trial registered with ClinicalTrials.gov (NCT 00608764).

Expiratory reactance abnormalities in patients with expiratory dynamic airway collapse: a new application of impulse oscillometry

Expiratory dynamic airways collapse (EDAC) is a condition that affects the central airways; it is not well characterised physiologically, with relatively few studies. We sought to characterise impulse oscillometry (IOS) features of EDAC in patients with normal spirometry. Expiratory data were hypothesised to be the most revealing. In addition, we compared IOS findings in chronic obstructive pulmonary disease (COPD) patients with and without EDAC.

EDAC was identified at bronchoscopy as 75–100% expiratory closure at the carina or bilateral main bronchi. Four patient groups were compared: controls with no EDAC and normal lung function; lone EDAC with normal lung function; COPD-only patients; and COPD patients with EDAC.

38 patients were studied. Mean IOS data z-scores for EDAC compared to controls showed significantly higher reactance (X) values including X at 5 Hz, resonance frequency and area under the reactance curve (A_X). EDAC showed significantly greater expiratory/inspiratory differences in all IOS data compared to controls. Stepwise logistic regression showed that resonant frequency best discriminated between EDAC and normal control, whereas classification and regression tree analysis found A_X ≥3.523 to be highly predictive for EDAC in cases with normal lung function (14 out of 15 cases, and none out of eight controls).

These data show a new utility of IOS: detecting EDAC in patients with normal lung function.

Central airway expiratory dynamic airway collapse can be “silent” on breathing tests, but impulse oscillometry can reveal ithttp://ow.ly/9oIb30lIOka

Exertional Dyspnea and Excessive Dynamic Airway Collapse

Excessive dynamic airway collapse is a relatively new diagnosis separate from tracheobronchomalacia that is manifested by functional collapse of the large airways. Most commonly described in patients with underlying obstructive lung disease such as chronic obstructive pulmonary disease and asthma, it may contribute to increased dyspnea, cough, or exacerbations. There are few data published on the role of excessive dynamic airway collapse as related specifically to exercise. It was recently described as the cause for exertional dyspnea in individuals without underlying lung disease.

Exercise-associated Excessive Dynamic Airway Collapse in Military Personnel

RATIONALE

Evaluation of military personnel for exertional dyspnea can present a diagnostic challenge, given multiple unique factors that include wide variation in military deployment. Initial consideration is given to common disorders such as asthma, exercise-induced bronchospasm, and inducible laryngeal obstruction. Excessive dynamic airway collapse has not been reported previously as a cause of dyspnea in these individuals.

OBJECTIVES

To describe the clinical and imaging characteristics of military personnel with exertional dyspnea who were found to have excessive dynamic collapse of large airways during exercise.

METHODS

After deployment to Afghanistan or Iraq, 240 active U.S. military personnel underwent a standardized evaluation to determine the etiology of persistent dyspnea on exertion. Study procedures included full pulmonary function testing, impulse oscillometry, exhaled nitric oxide measurement, methacholine challenge testing, exercise laryngoscopy, cardiopulmonary exercise testing, and fiberoptic bronchoscopy. Imaging included high-resolution computed tomography with inspiratory and expiratory views. Selected individuals underwent further imaging with dynamic computed tomography.

MEASUREMENTS AND MAIN RESULTS

A total of five men and one woman were identified as having exercise-associated excessive dynamic airway collapse on the basis of the following criteria: (1) exertional dyspnea without resting symptoms, (2) focal expiratory wheezing during exercise, (3) functional collapse of the large airways during bronchoscopy, (4) expiratory computed tomographic imaging showing narrowing of a large airway, and (5) absence of underlying apparent pathology in small airways or pulmonary parenchyma. Identification of focal expiratory wheezing correlated with bronchoscopic and imaging findings.

CONCLUSIONS

Among 240 military personnel evaluated after presenting with postdeployment exertional dyspnea, a combination of symptoms, auscultatory findings, imaging, and visualization of the airways by bronchoscopy identified six individuals with excessive dynamic central airway collapse as the sole apparent cause of dyspnea. Exercise-associated excessive dynamic airway collapse should be considered in the differential diagnosis of exertional dyspnea.

Tracheal collapse diagnosed by multidetector computed tomography: evaluation of different image analysis methods

Background: The gold standard for diagnosing excessive tracheal collapse is still evaluation during bronchoscopy. Today, multidetector computed tomography (MDCT) is used to confirm a suspicion of abnormal tracheal collapse. There is no gold standard for computed tomography (CT) image analysis of tracheal collapse.

Purpose: To evaluate four different methods for the diagnosis of tracheal collapse using the images obtained through MDCT to help clinicians evaluate the images in daily practice.

Objectives: 374 consecutive high-resolution CT scans with full inspiratory and end-expiratory CT scans were retrospectively analyzed.

Methods: The images were analyzed in four different ways. The degree of collapse was based on cross-sectional areas of individual locations or volumes of entire regions: (1) 1 cm above the carina, (2) the level of maximal collapse of the trachea, (3) the entire region from the carina to the thoracic inlet, and (4) the trachea and bronchial region as defined by the software.

Results: We compared three existing and one new method for image analysis of tracheal collapse by MDCT. The prevalence of tracheal collapse varied from 10.7% to 19.5% in this cohort of patients suffering from mixed lung diseases when using an expiratory collapse of ≥50% as a threshold. The four methods were comparable with highly significant Pearsons correlation coefficients (0.764–0.856). However, the four methods identified different patients with collapse of ≥50%. There was no correlation between symptoms and the degree of collapse.

Conclusion: The different methods identify tracheal collapse in different patients. Hence, the diagnosis of excessive tracheal collapse can not rely solely on MDCT images. Generally, there is a poor correlation between symptoms and the degree of collapse in the different methods. However, when using the maximal collapse, there is some correlation with symptoms. When in doubt regarding the diagnosis, further investigations, such as bronchoscopy, should be carried out.

Glottis Closure Influences Tracheal Size Changes in Inspiratory and Expiratory CT in Patients with COPD

RATIONALE AND OBJECTIVES

The opened or closed status of the glottis might influence tracheal size changes in inspiratory and expiratory computed tomography (CT) scans. We investigated if the glottis status makes the tracheal collapse differently correlate with lung volume difference between inspiratory and expiratory CT scans.

MATERIALS AND METHODS

Forty patients with chronic obstructive pulmonary disease whose glottis was included in the acquired scanned volume for lung CT were divided into two groups: 16 patients with the glottis closed in both inspiratory and expiratory CT, and 24 patients with the glottis open in at least one CT acquisition. Lung inspiratory (Vinsp) and expiratory (Vexp) volumes were automatically computed and lung ΔV was calculated using the following formula: (Vinsp - Vexp)/Vinsp × 100. Two radiologists manually measured the anteroposterior diameter and cross-sectional area of the trachea 1 cm above the aortic arch and 1 cm above the carina. Tracheal collapse was then calculated and correlated with lung ΔV.

RESULTS

In the 40 patients, the correlations between tracheal Δanteroposterior diameter and Δcross-sectional area at each level and lung ΔV ranged between 0.68 and 0.74 (ρ) at Spearman rank correlation test. However, in the closed glottis group, the correlations were higher for all measures at the two levels (ρ range: 0.84-0.90), whereas in the open glottis group, correlations were low and not statistically significant (ρ range: 0.29-0.34) at the upper level, and moderate at the lower level (ρ range: 0.51-0.55).

CONCLUSIONS

A closed or open glottis influences the tracheal size change in inspiratory and expiratory CT scans. With closed glottis, the tracheal collapse shows a stronger correlation with the lung volume difference between inspiratory and expiratory CT scans.

Our Experience on Silicone Y-Stent for Severe COPD Complicated With Expiratory Central Airway Collapse

BACKGROUND

Expiratory central airway collapse (ECAC) is abnormal central airway narrowing during expiration. ECAC involves 2 different pathophysiological entities as tracheobronchomalacia and excessive dynamic airway collapse (EDAC). Although the exact cause is unknown, chronic obstructive pulmonary disease (COPD) is frequently accompanied by ECAC. Although there are various publications on the relationship between COPD and ECAC, there are very few data for stent placement in patients with tracheobronchomalacia accompanied severe COPD. We share our results for stenting in ECAC among patients with severe COPD.

METHODS

The data in this case series were collected retrospectively. The ECAC diagnosis was made during flexible bronchoscopy with severe COPD. Silicone Y-stents were placed via rigid bronchoscopy under general anesthesia.

RESULTS

A total of 9 patients' (7 men) data were evaluated with an average age of 67±10.73 years. One patient experienced stent migration on the second day of stenting prompting stent removal. Another patient died 1 month after stenting. Consequently, we evaluated the follow-up data of remaining 7 patients. The changes in forced expiratory volume 1 was not significant for these 7 cases (P=0.51). The modified Medical Research Council (mMRC) score improvement was statistically significant (P=0.03). Functional status improvement was observed in 4 of 7 patients. Of the 7 patients, mean additional follow-up bronchoscopic interventions requirement was 2.2 times.

CONCLUSIONS

Our study showed significant decrease in mMRC score with stenting for ECAC in severe COPD. For 2 patients, we experienced severe complications during short-term follow-up period after stenting. Additional follow-up bronchoscopic interventions were required.

Association Between Expiratory Central Airway Collapse and Respiratory Outcomes Among Smokers

IMPORTANCE

Central airway collapse greater than 50% of luminal area during exhalation (expiratory central airway collapse [ECAC]) is associated with cigarette smoking and chronic obstructive pulmonary disease (COPD). However, its prevalence and clinical significance are unknown.

OBJECTIVE

To determine whether ECAC is associated with respiratory morbidity in smokers independent of underlying lung disease.

DESIGN, SETTING, AND PARTICIPANTS

Analysis of paired inspiratory-expiratory computed tomography images from a large multicenter study (COPDGene) of current and former smokers from 21 clinical centers across the United States. Participants were enrolled from January 2008 to June 2011 and followed up longitudinally until October 2014. Images were initially screened using a quantitative method to detect at least a 30% reduction in minor axis tracheal diameter from inspiration to end-expiration. From this sample of screen-positive scans, cross-sectional area of the trachea was measured manually at 3 predetermined levels (aortic arch, carina, and bronchus intermedius) to confirm ECAC (>50% reduction in cross-sectional area).

EXPOSURES

Expiratory central airway collapse.

MAIN OUTCOMES AND MEASURES

The primary outcome was baseline respiratory quality of life (St George's Respiratory Questionnaire [SGRQ] scale 0 to 100; 100 represents worst health status; minimum clinically important difference [MCID], 4 units). Secondary outcomes were baseline measures of dyspnea (modified Medical Research Council [mMRC] scale 0 to 4; 4 represents worse dyspnea; MCID, 0.7 units), baseline 6-minute walk distance (MCID, 30 m), and exacerbation frequency (events per 100 person-years) on longitudinal follow-up.

RESULTS

The study included 8820 participants with and without COPD (mean age, 59.7 [SD, 6.9] years; 4667 [56.7%] men; 4559 [51.7%] active smokers). The prevalence of ECAC was 5% (443 cases). Patients with ECAC compared with those without ECAC had worse SGRQ scores (30.9 vs 26.5 units; P < .001; absolute difference, 4.4 [95% CI, 2.2-6.6]) and mMRC scale scores (median, 2 [interquartile range [IQR], 0-3]) vs 1 [IQR, 0-3]; P < .001]), but no significant difference in 6-minute walk distance (399 vs 417 m; absolute difference, 18 m [95% CI, 6-30]; P = .30), after adjustment for age, sex, race, body mass index, forced expiratory volume in the first second, pack-years of smoking, and emphysema. On follow-up (median, 4.3 [IQR, 3.2-4.9] years), participants with ECAC had increased frequency of total exacerbations (58 vs 35 events per 100 person-years; incidence rate ratio [IRR], 1.49 [95% CI, 1.29-1.72]; P < .001) and severe exacerbations requiring hospitalization (17 vs 10 events per 100 person-years; IRR, 1.83 [95% CI, 1.51-2.21]; P < .001).

CONCLUSIONS AND RELEVANCE

In a cross-sectional analysis of current and former smokers, the presence of ECAC was associated with worse respiratory quality of life. Further studies are needed to assess long-term associations with clinical outcomes.

Excessive Dynamic Airway Collapse of the Lower Airway: A Cause for Persistent Sleep Disordered Breathing after Tracheostomy

ABSTRACT

Tracheostomy has demonstrated effectiveness in the control of obstructive sleep apnea (OSA) in most patients; however, current evidence suggests significant sleep disordered breathing may persist, particularly in morbidly obese individuals. While several mechanisms have been proposed to explain this phenomenon, we demonstrate evidence of a previously unidentified pathophysiology: excessive dynamic airway collapse (EDAC) of the lower airway. We present the case of a 62-year-old woman status post tracheostomy with persistent dyspnea in the supine position. Both radiographic and bronchoscopic images demonstrate prolapse of the posterior membranous trachea at the level of the trachea and mainstem bronchi with partial or complete obstruction. The prolapse was completely relieved with upright positioning or positive airway pressure. This case illustrates a novel mechanism of post-tracheostomy sleep disordered breathing in obese individuals and emphasizes the need to consider follow-up polysomnography after tracheostomy in this patient population, especially those with persistent symptoms related to sleep or the supine position.

Comorbidities and Chronic Obstructive Pulmonary Disease: Prevalence, Influence on Outcomes, and Management

Comorbidities impact a large proportion of patients with chronic obstructive pulmonary disease (COPD), with over 80% of patients with COPD estimated to have at least one comorbid chronic condition. Guidelines for the treatment of COPD are just now incorporating comorbidities to their management recommendations of COPD, and it is becoming increasingly clear that multimorbidity as well as specific comorbidities have strong associations with mortality and clinical outcomes in COPD, including dyspnea, exercise capacity, quality of life, healthcare utilization, and exacerbation risk. Appropriately, there has been an increased focus upon describing the burden of comorbidity in the COPD population and incorporating this information into existing efforts to better understand the clinical and phenotypic heterogeneity of this group. In this article, we summarize existing knowledge about comorbidity burden and specific comorbidities in COPD, focusing on prevalence estimates, association with outcomes, and existing knowledge about treatment strategies.

Excessive Dynamic Airway Collapse: An Unexpected Contributor to Respiratory Failure in a Surgical Patient

Central airway collapse plays a significant, underrecognized role in respiratory failure after extubation of critically ill patients. Historically, airway collapse has been attributed to tracheomalacia (TM), softening of the cartilage in the trachea and other large airways. More recently, excessive dynamic airway collapse (EDAC) has been described as a distinct process unrelated to a loss of cartilaginous airway support. EDAC is caused by the posterior wall of the trachea bulging forward and causing airway obstruction during exhalation. This process is exaggerated when intrathoracic pressure is increased and results in a clinical picture of coughing, difficulty clearing secretions, dyspnea, and stridor. The increased use of computerized tomography and fiberoptic bronchoscopy has identified varying degrees of EDAC and TM in both symptomatic and asymptomatic individuals. This has led to renewed consideration of airway collapse and the different processes that contribute to it. Here we describe a 43-year-old morbidly obese patient who failed repeated attempts at extubation after elective hysterectomy. We will discuss the processes of EDAC and TM, describe how this condition contributed to this patient's respiratory failure, and review diagnosis and management options.

Is intrathoracic tracheal collapsibility correlated to clinical phenotypes and sex in patients with COPD?

A substantial proportion of patients with chronic obstructive pulmonary disease (COPD) develops various degree of intrathoracic tracheal collapsibility. We studied whether the magnitude of intrathoracic tracheal collapsibility could be different across clinical phenotypes and sex in COPD. Intrathoracic tracheal collapsibility measured at paired inspiratory-expiratory low dose computed tomography (CT) and its correlation with clinical, functional, and CT-densitometric data were investigated in 69 patients with COPD according to their predominant conductive airway or emphysema phenotypes and according to sex. Intrathoracic tracheal collapsibility was higher in patients with predominant conductive airway disease (n=28) and in females (n=27). Women with a predominant conductive airway phenotype (n=10) showed a significantly greater degree of collapsibility than women with predominant emphysema (28.9%±4% versus 11.6%±2%; P<0.001). Intrathoracic tracheal collapsibility was directly correlated with inspiratory-expiratory volume variation at CT and with forced expiratory volume (1 second), and inversely correlated with reduced CT lung density and functional residual capacity. Intrathoracic tracheal collapsibility was not correlated with cough and wheezing; however, intrathoracic tracheal collapsibility and clinical phenotypes of COPD are closely correlated. In patients with a predominant emphysematous phenotype, a reduced collapsibility may reflect the mechanical properties of the stiff hyperinflated emphysematous lung. The high collapsibility in patients with predominant airway disease, mild airway obstruction, and in women with this phenotype may reflect chronic airway inflammation. The lack of relationship with such symptoms as wheezing, cough, and dyspnea could indicate that intrathoracic tracheal collapsibility itself should be considered neither an abnormal feature of COPD nor a relevant clinical finding.

Potential role of the airway wall in the asthma of obesity

The pathogenesis of late-onset TH2-low asthma in obesity is thought to be related to weight-related decreases in lung volume, but why only a subset of individuals with obesity develop this condition is unknown. We tested the hypothesis that natural variations in both airway wall stiffness and airway wall thickness could lead to a subpopulation of hyperresponsive individuals exhibiting the symptoms of asthma in the setting of obesity. Increases in airway resistance (Raw) after airway smooth muscle stimulation were simulated using a computational model of an elastic airway embedded in elastic parenchyma. Using a range of randomly chosen values for both airway wall stiffness and thickness, we determined the resulting probability distributions of Raw responsiveness for a variety of different levels of transpulmonary pressure (Ptp). As Ptp decreased from 5 to 1 cmH2O, the resulting distributions of Raw moved toward progressively higher levels of responsiveness. With appropriate choices for the mean and standard deviation of the parameter that controls either airway wall stiffness or thickness, the model predicts a relationship between airway hyperresponsiveness and body mass index that is similar to that which has been reported in populations with obesity. We conclude that natural variations in airway wall mechanics and geometry between different individuals can potentially explain why an increasing percentage of the population exhibits the symptoms of asthma as the obesity of the population increases.

Pathogenesis of hyperinflation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a preventable and treatable lung disease characterized by airflow limitation that is not fully reversible. In a significant proportion of patients with COPD, reduced lung elastic recoil combined with expiratory flow limitation leads to lung hyperinflation during the course of the disease. Development of hyperinflation during the course of COPD is insidious. Dynamic hyperinflation is highly prevalent in the advanced stages of COPD, and new evidence suggests that it also occurs in many patients with mild disease, independently of the presence of resting hyperinflation. Hyperinflation is clinically relevant for patients with COPD mainly because it contributes to dyspnea, exercise intolerance, skeletal muscle limitations, morbidity, and reduced physical activity levels associated with the disease. Various pharmacological and nonpharmacological interventions have been shown to reduce hyperinflation and delay the onset of ventilatory limitation in patients with COPD. The aim of this review is to address the more recent literature regarding the pathogenesis, assessment, and management of both static and dynamic lung hyperinflation in patients with COPD. We also address the influence of biological sex and obesity and new developments in our understanding of hyperinflation in patients with mild COPD and its evolution during progression of the disease.