Association Between Expiratory Central Airway Collapse and Respiratory Outcomes Among Smokers

Gender, tobacco and chronic obstructive pulmonary disease: analysis of the 2020 National Health Interview Survey

RATIONALE

Recent studies describe an increasing prevalence of chronic obstructive pulmonary disease (COPD) and higher COPD exacerbation rates among women compared with men despite lower average cigarette use, which has raised the question of whether women are more susceptible to the effects of tobacco smoke. We examined associations between gender, cigarette smoking and COPD in a national dataset.

METHODS

We used cross-sectional data for US respondents aged ≥40 years from the 2020 National Health Interview Survey (NHIS). Weighted multivariable logistic regressions assessed the relationship between gender and respondent-reported physician-diagnosed COPD, adjusting for tobacco use and sociodemographic covariates. Additional analyses were performed to determine if the relationship between cigarette smoking and COPD was modified by gender.

RESULTS

Women had a higher COPD prevalence (7.8%) than men (6.5%) despite lower cigarette smoke exposure. Women were less likely to have ever smoked, and among respondents who had smoked, women had a lower average pack-year history compared with men. In multivariable regressions, female gender was associated with a higher risk of COPD (adjusted risk ratio 1.47, 95% CI 1.30 to 1.65) and the relative risk was similar for respondents both with and without a history of smoking. Moreover, there was no significant interaction between gender and smoking status or gender and pack-year exposure relating to COPD prevalence.

CONCLUSIONS

Among adults aged ≥40 years, women had a roughly 50% greater risk of COPD than men. Higher susceptibility to cigarette smoking in women did not explain the difference.

Patient-centred outcome following endoscopic management of benign central airway obstruction

PURPOSE

To examine patient-centred outcome following endoscopic treatment of central airway stenosis in terms of days alive and out of hospital (DAOH), need for re-intervention, and complications, with reference to aetiology of disease and applied treatment methodology.

METHODS

Analyses were based on data from consecutive adult patients treated endoscopically for benign central airway obstruction at Aarhus University Hospital from 2012 to 2022, with a minimum follow-up of one year. DAOH was calculated for 30 and 365 days. Complications were graded based on the Clavien-Dindo classification. Univariate and multivariate analyses were performed to identify predictors for DAOH, re-intervention and complications.

RESULTS

82 consecutive adult patients underwent endoscopic treatment during the period of inclusion, comprising a total of 175 dilatations, 42 benign tumour resections, and 67 stent insertions. Multiple interventions and short re-intervention intervals was more likely amongst patients reporting significant preoperative dyspnoea or requiring preoperative respiratory support, as well as patients treated with endoscopic insertion of silicone stents. The overall complication rate per procedure was 11.7%, and complications were more likely to occur in patients with high age, high BMI and comorbidity. Overall DAOH during the first year after intervention was 343 days, lowest amongst patients with tracheobronchomalacia or severe airway stenosis, and in those who underwent endoscopic stent insertion.

CONCLUSION

Endoscopic treatment is a safe and viable intervention in the management of benign central airway obstruction in adults with few complications and a high overall outcome.

COPD-Associated Expiratory Central Airway Collapse: Current Concepts and New Perspectives

TOPIC IMPORTANCE

COPD-associated expiratory central airway collapse (ECAC) is a frequently overlooked benign airway obstructive disease with complex causes and unclear pathologic and physiologic mechanisms. Although interventions such as noninvasive positive pressure ventilation, airway stenting, and tracheobronchoplasty have shown definite efficacy in the treatment of COPD-associated ECAC, the diagnosis and treatment of this disease remain challenging. This review provides a systematic evaluation and outlook on the epidemiologic features, causes, pathophysiologic characteristics, clinical manifestations, diagnosis, and treatment of COPD-associated ECAC.

REVIEW FINDINGS

COPD-associated ECAC is a benign airway narrowing disease with atypical clinical symptoms and unknown incidence and pathogenesis. Bronchoscopy is considered the gold standard technique for diagnosis of COPD-associated ECAC, with dynamic biphasic CT imaging as an alternative noninvasive method. Noninvasive ventilation treatment can be continued on a long-term basis. Temporary airway stents can alleviate acute and severe tracheobronchomalacia. Long-term stent implantation can be considered after a risk to benefit assessment. Although tracheobronchoplasty has a definite therapeutic effect in patients with severe tracheobronchomalacia, perioperative complications remain a serious issue, and long-term efficacy observation is required. Traditional chinese medicine, other positive expiratory pressure therapies, and lung transplantation have shown potential with limited evidence.

SUMMARY

Although COPD-associated ECAC is attracting considerable attention, its pathophysiologic mechanisms, diagnosis, and management are full of challenges. In the future, randomized controlled trials on different therapies using patient-centered outcomes, cost-effective analysis on different interventions, and consensus guidelines on COPD-associated ECAC will be urgently needed.

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.

Complete expiratory central airway collapse at general anesthesia recovery: a case report

Expiratory central airway collapse is a degenerative tracheobronchial disease that is often overlooked because of its nonspecific clinical features. A man was admitted for evaluation of tracheal nodules. Following bronchoscopic biopsy, a significant increase in airway pressure occurred during anesthesia recovery. Laryngospasm was suspected, and tracheal intubation was performed. Bronchoscopy revealed an almost completely collapsed tracheal lumen. A Y-shaped silicone stent was placed using a rigid bronchoscope to support the airway, allowing spontaneous ventilation to resume. A retrospective review of the images suggested a diagnosis of excessive dynamic airway collapse. The silicone stent was removed after 2 weeks because of discomfort, and no subsequent dyspnea was observed. This case highlights that excessive dynamic airway collapse is easily missed. Anesthesiologists must be educated on this condition, maintain a thorough understanding of the patient's state and illness, and have emergency airway equipment readily available to restore ventilation promptly in cases of severe airway collapse.

[CT imaging of chronic obstructive pulmonary disease: What aspects and what role?]

Chronic obstructive pulmonary disease (COPD), commonly defined as irreversible airflow limitation, is associated with specific morphological changes involving all three parts of the lung, namely the bronchi, parenchyma and pulmonary vessels. In vivo imaging, with its ability to describe the different types of lung alterations and their regional distribution, helps to elucidate the relationship between lung structure and respiratory function. High-resolution computed tomography (CT) of the lung is the imaging modality best suited to assessing the pathological changes associated with airflow obstruction occurring in COPD. Over the last few decades, numerous studies have demonstrated the role of CT as a morphological and functional method conducive to the phenotyping of COPD patients. This review proposes to examine the data on CT imaging of COPD with a critical approach to recent data, and to determine the extent to which CT could be integrated into care or clinical research on patients with this/these disease(s).

Lung imaging in COPD and asthma

Chronic obstructive pulmonary disease (COPD) and asthma are common lung diseases with heterogeneous clinical presentations. Lung imaging allows evaluations of underlying pathophysiological changes and provides additional personalized approaches for disease management. This narrative review provides an overview of recent advances in chest imaging analysis using various modalities, such as computed tomography (CT), dynamic chest radiography, and magnetic resonance imaging (MRI). Visual CT assessment localizes emphysema subtypes and mucus plugging in the airways. Dedicated software quantifies the severity and spatial distribution of emphysema and the airway tree structure, including the central airway wall thickness, branch count and fractal dimension of the tree, and airway-to-lung size ratio. Nonrigid registration of inspiratory and expiratory CT scans quantifies small airway dysfunction, local volume changes and shape deformations in specific regions. Lung ventilation and diaphragm movement are also evaluated on dynamic chest radiography. Functional MRI detects regional oxygen transfer across the alveolus using inhaled oxygen and ventilation defects and gas diffusion into the alveolar-capillary barrier tissue and red blood cells using inhaled hyperpolarized 129Xe gas. These methods have the potential to determine local functional properties in the lungs that cannot be detected by lung function tests in patients with COPD and asthma. Further studies are needed to apply these technologies in clinical practice, particularly for early disease detection and tailor-made interventions, such as the efficient selection of patients likely to respond to biologics. Moreover, research should focus on the extension of healthy life expectancy in patients at higher risk and with established diseases.

ACR Appropriateness Criteria® Tracheobronchial Disease

A variety of thoracic imaging modalities and techniques have been used to evaluate diseases of the trachea and central bronchi. This document evaluates evidence for the use of thoracic imaging in the evaluation of tracheobronchial disease, including clinically suspected tracheal or bronchial stenosis, tracheomalacia or bronchomalacia, and bronchiectasis. Appropriateness guidelines for initial imaging evaluation of tracheobronchial disease and for pretreatment planning or posttreatment evaluation are included. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Airway Stents for Excessive Central Airway Collapse: A Randomized Controlled Open-label Trial

BACKGROUND

Short-term airway stent placement (stent evaluation) has been employed to evaluate whether patients with excessive central airway collapse (ECAC) will benefit from tracheobronchoplasty. Although retrospective studies have explored the impact of stent placement on ECAC, prospective randomized controlled trials are absent.

METHODS

This was a randomized open-label trial comparing patients receiving airway stent placement and standard medical treatment (intervention group) versus standard medical treatment alone (control group) for ECAC. At baseline, patients' respiratory symptoms, self-reported measures, and functional capabilities were assessed. Follow-up evaluations occurred 7 to 14 days postintervention, with an option for the control group to crossover to stent placement. Follow-up evaluations were repeated in the crossover patients.

RESULTS

The study enrolled 17 patients in the control group [medical management (MM)] and 14 patients in the intervention group. At follow-up, 15 patients in the MM crossed over to the stent group, resulting in a total of 29 patients in the combined stent group (CSG). Subjectively (shortness of breath and cough), 45% of the CSG exhibited improvement with the intervention compared with just 12% in the MM. The modified St. George Respiratory Questionnaire score in the CSG improved significantly from 61.2 at baseline to 52.5 after stent placement (-8.7, P = 0.04). With intervention, the 6-minute walk test in CSG improved significantly from 364 meters to 398 meters (34 m, P < 0.01). The MM did not show a significant change in the St. George Respiratory Questionnaire score or 6-minute walk test distance.

CONCLUSION

Short-term airway stent placement in patients with ECAC significantly improves respiratory symptoms, quality of life, and exercise capacity.

Ultralow-Dose Dynamic Expiratory CT and Repeated Imaging Enhance Evaluation for Tracheomalacia

OBJECTIVE

This study aims to determine if a novel imaging protocol (ultralow-dose dynamic expiratory computed tomography [CT] with repeated imaging) identifies tracheomalacia (TM) more reliably than traditional dynamic tracheal CT.

METHODS

We performed a retrospective evaluation of 184 consecutive ultralow-dose dynamic CTs for TM during 2017. The protocol obtains images during 1 inspiration and 2 forced expirations. Tracheal narrowing during both expirations (airway narrowing [percentage] during first dynamic expiration CT [DE1], airway narrowing [percentage] during second dynamic expiration CT [DE2]) was reported as a percentage of inspiratory area. We identified maximum narrowing of each patient's sequence (maximum narrowing [percentage] on either dynamic expiration CT [DEmax] = greatest narrowing of DE1 or DE2) and compared DE1, DE2, and DEmax in individual studies and between patients. Outcomes included frequency of TM, tracheal narrowing, and severity. Reliability was assessed by comparing tracheal area narrowing and TM grade.

RESULTS

There was significantly more airway narrowing using 2 expiratory image acquisitions. Average DEmax tracheal area was 12% narrower than DE1 alone and 21% worse than DE2 alone (both P < 0.001). Using DEmax, TM was diagnosed 35% more often than DE1 alone and 31% more often than DE2 alone ( P < 0.001). DEmax identified more severe distribution of TM compared with DE1 or DE2 alone ( P < 0.001). Reliability between DE1 and DE2 was good for tracheal narrowing and moderate for TM grade. The mean effective radiation dose was 2.41 millisievert (mSv) for routine inspiration CT and 0.07 mSv for each dynamic expiration CT (total effective radiation, 2.55 mSv).

CONCLUSIONS

Dynamic expiration CT with 2 expiratory image acquisitions enhanced evaluation of TM, minimally increased radiation dose, and should be considered as a noninvasive screening option.

Gender differences in association between expiratory dynamic airway collapse and severity of obstructive sleep apnea

OBJECTIVES

Repetitive unbalances and tensions generated by inspiratory efforts against an obstructive upper airway during sleep predispose the development of expiratory central airway collapse. In addition, structures of the upper airway between men and women have differences and could be the reasons for differences in obstructive sleep apnea (OSA) prevalence between genders. The present study aimed to evaluate the association between parameters of expiratory dynamic tracheal collapse measured using chest multidetector CT and objectively measured OSA severity between men and women.

MATERIALS AND METHODS

A total of 901 participants who underwent chest CT and overnight in-home polysomnography from the Korean Genome and Epidemiology Study were cross-sectionally analyzed (women: 46.2%). The participants were divided into three groups based on OSA severity by apnea-hypopnea index (AHI). Multivariate linear regression analysis was performed to determine the effects of central airway collapse after adjustment for cardiovascular-related covariates.

RESULTS

In a multivariate analysis, percentages of expiratory lumen structure reductions involving area, diameter, and perimeter were associated with AHI (all p values < 0.05) and with OSA severity (moderate-to-severe OSA than no OSA: β = 3.30%, p = 0.03; β = 2.05%, p = 0.02; β = 1.97%, p = 0.02, respectively) in women, whereas men had only a greater percentage of expiratory wall thickness reduction in moderate-to-severe OSA than no OSA (β = 0.72%, p = 0.003). In addition, women with both mild OSA and moderate-to-severe OSA had higher expiratory tracheal collapse than men without OSA, and a moderate effect of sex was observed (p for interaction = 0.007).

CONCLUSION

The expiratory dynamic tracheal collapse was independently associated with severity of OSA in women than in men.

CLINICAL RELEVANCE STATEMENT

Differences of pharyngeal structures and inherent features of airways by genders may affect the dissimilarities in vulnerability to sleep apnea between men and women.

KEY POINTS

• The expiratory dynamic tracheal collapse was independently associated with severity of OSA in women than in men. • Women with over mild OSA had higher expiratory tracheal collapse than men without OSA, and moderate effect of sex was observed. • Structural differences of airway may affect differences in susceptibility of sleep apnea between genders.

Advances in COPD imaging using CT and MRI: linkage with lung physiology and clinical outcomes

Recent years have witnessed major advances in lung imaging in patients with COPD. These include significant refinements in images obtained by computed tomography (CT) scans together with the introduction of new techniques and software that aim for obtaining the best image whilst using the lowest possible radiation dose. Magnetic resonance imaging (MRI) has also emerged as a useful radiation-free tool in assessing structural and more importantly functional derangements in patients with well-established COPD and smokers without COPD, even before the existence of overt changes in resting physiological lung function tests. Together, CT and MRI now allow objective quantification and assessment of structural changes within the airways, lung parenchyma and pulmonary vessels. Furthermore, CT and MRI can now provide objective assessments of regional lung ventilation and perfusion, and multinuclear MRI provides further insight into gas exchange; this can help in structured decisions regarding treatment plans. These advances in chest imaging techniques have brought new insights into our understanding of disease pathophysiology and characterising different disease phenotypes. The present review discusses, in detail, the advances in lung imaging in patients with COPD and how structural and functional imaging are linked with common resting physiological tests and important clinical outcomes.

Body positioning-related laryngeal narrowing pattern and expiratory mechanical constraints in advanced chronic obstructive pulmonary disease: A case report

We previously reported that laryngeal widening led to improved exercise tolerance in COPD. However, it is not clear whether laryngeal narrowing occurs as a compensatory response to tracheal movement or is affected by posture. Here, we report the case of an advanced COPD patient whose more prolonged expiration in a head-forward leaning position compared with that in a neck-extended position occurred with an excessive duration of severe laryngeal narrowing without tracheal obstruction, which led to exercise intolerance with expiratory mechanical constraints. This case provided useful insights into the regulation of the upper airway with body positioning for improving exercise tolerance.

Tracheobronchomalacia: an unusual cause of debilitating dyspnoea and its surgical management

Tracheobronchomalacia (TBM) is a progressive weakening of the airways, leading to collapse and dyspnoea. TBM can be misdiagnosed when multiple chronic conditions accompany it. Tracheobronchoplasty (TBP) is indicated for severe symptomatic TBM, diagnosed by bronchoscopy and CT thorax. We report the case of a patient who underwent tracheal resection and reconstruction for continuing dyspnoea post argon therapy, TBP and a failure to tolerate extracorporeal membrane oxygenation-assisted Y-stent insertion. Relevant background history includes asthma, sleep apnoea, reflux, cardiomyopathy and a high body mass index. Bronchoscopy postreconstruction showed patent airways. Airway reconstruction was a viable management option for this patient's TBM. TBP is a treatment option for TBM. In this case, tracheal resection was required to sustain benefit. In addition, surveillance bronchoscopies will be carried out every year.

Phenotypes, Etiotypes, and Endotypes of Exacerbations of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease is a major health problem with a high prevalence, a rising incidence, and substantial morbidity and mortality. Its course is punctuated by acute episodes of increased respiratory symptoms, termed exacerbations of chronic obstructive pulmonary disease (ECOPD). ECOPD are important events in the natural history of the disease, as they are associated with lung function decline and prolonged negative effects on quality of life. The present-day therapy for ECOPD with short courses of antibiotics and steroids and escalation of bronchodilators has resulted in only modest improvements in outcomes. Recent data indicate that ECOPD are heterogeneous, raising the need to identify distinct etioendophenotypes, incorporating traits of the acute event and of patients who experience recurrent events, to develop novel and targeted therapies. These characterizations can provide a complete clinical picture, the severity of which will dictate acute pharmacological treatment, and may also indicate whether a change in maintenance therapy is needed to reduce the risk of future exacerbations. In this review we discuss the latest knowledge of ECOPD types on the basis of clinical presentation, etiology, natural history, frequency, severity, and biomarkers in an attempt to characterize these events.

Quantitative CT Scan Imaging of the Airways for Diagnosis and Management of Lung Disease

CT scan imaging provides high-resolution images of the lungs in patients with chronic respiratory diseases. Extensive research over the last several decades has focused on developing novel quantitative CT scan airway measurements that reflect abnormal airway structure. Despite many observational studies demonstrating that associations between CT scan airway measurements and clinically important outcomes such as morbidity, mortality, and lung function decline, few quantitative CT scan measurements are applied in clinical practice. This article provides an overview of the relevant methodologic considerations for implementing quantitative CT scan airway analyses and provides a review of the scientific literature involving quantitative CT scan airway measurements used in clinical or randomized trials and observational studies of humans. We also discuss emerging evidence for the clinical usefulness of quantitative CT scan imaging of the airways and discuss what is required to bridge the gap between research and clinical application. CT scan airway measurements continue to improve our understanding of disease pathophysiologic features, diagnosis, and outcomes. However, a literature review revealed a need for studies evaluating clinical benefit when quantitative CT scan imaging is applied in the clinical setting. Technical standards for quantitative CT scan imaging of the airways and high-quality evidence of clinical benefit from management guided by quantitative CT scan imaging of the airways are required.

The utility of quantitative computed tomography in cohort studies of chronic obstructive pulmonary disease: a narrative review

Background and Objective

Chronic obstructive pulmonary disease (COPD) is a significant contributor to global morbidity and mortality. Quantitative computed tomography (QCT), a non-invasive imaging modality, offers the potential to assess lung structure and function in COPD patients. Amidst the coronavirus disease 2019 (COVID-19) pandemic, chest computed tomography (CT) scans have emerged as a viable alternative for assessing pulmonary function (e.g., spirometry), minimizing the risk of aerosolized virus transmission. However, the clinical application of QCT measurements is not yet widespread enough, necessitating broader validation to determine its usefulness in COPD management.

Methods

We conducted a search in the PubMed database in English from January 1, 2013 to April 20, 2023, using keywords and controlled vocabulary related to QCT, COPD, and cohort studies.

Key Content and Findings

Existing studies have demonstrated the potential of QCT in providing valuable information on lung volume, airway geometry, airway wall thickness, emphysema, and lung tissue density in COPD patients. Moreover, QCT values have shown robust correlations with pulmonary function tests, and can predict exacerbation risk and mortality in patients with COPD. QCT can even discern COPD subtypes based on phenotypic characteristics such as emphysema predominance, supporting targeted management and interventions.

Conclusions

QCT has shown promise in cohort studies related to COPD, since it can provide critical insights into the pathogenesis and progression of the disease. Further research is necessary to determine the clinical significance of QCT measurements for COPD management.

Influence of Pulsatility and Inflow Waveforms on Tracheal Airflow Dynamics in Healthy Older Adults

Tracheal collapsibility is a dynamic process altering local airflow dynamics. Patient-specific simulation is a powerful technique to explore the physiological and pathological characteristics of human airways. One of the key considerations in implementing airway computations is choosing the right inlet boundary conditions that can act as a surrogate model for understanding realistic airflow simulations. To this end, we numerically examine airflow patterns under the influence of different profiles, i.e., flat, parabolic, and Womersley, and compare these with a realistic inlet obtained from experiments. Simulations are performed in ten patient-specific cases with normal and rapid breathing rates during the inhalation phase of the respiration cycle. At normal breathing, velocity and vorticity contours reveal primary flow structures on the sagittal plane that impart strength to cross-plane vortices. Rapid breathing, however, encounters small recirculation zones. Quantitative flow metrics are evaluated using time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI). Overall, the flow metrics encountered in a real velocity profile are in close agreement with parabolic and Womersley profiles for normal conditions, however, the Womersley inlet alone conforms to a realistic profile under rapid breathing conditions.

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.

Pneumatic stenting in the surgical candidacy assessment for cough variant expiratory central airway collapse

Expiratory Central Airway Collapse (ECAC) is a multifactorial, underdiagnosed entity that poses unique challenges. Airway stenting is used as a predictor for successful outcomes after central airway stabilization surgery via tracheobronchoplasty (TBP). This approach may pose suboptimal performance in certain ECAC variants. We hypothesize that Continuous Positive Airway Pressure (CPAP), used as a pneumatic stent, could be a non-invasive alternative to evaluate surgical candidacy in cough-predominant ECAC presentations. We report on a 67-year-old female with a history of chronic cough and confirmed ECAC. After optimization of medical therapy without significant relief and unsuccessful stent trial. We opted to perform CPAP trial during exercise, the patient exercised on a treadmill, and CPAP was applied at two levels (9 cmH₂O, 11 cmH₂O). The use of CPAP was associated with resolution of cough and a decrease in exercise-related perceived exertion. Applying CPAP during exercise may be a promising alternative to stent trials to determine patients' candidacy for surgical management of cough-predominant ECAC.

Association of dysanapsis with mortality among older adults

Dysanapsis – an anthropometric mismatch between airway tree calibre and lung size that is common in the general population – is strongly associated with all-cause mortality and increases susceptibility to tobacco smoking-related diseases https://bit.ly/42oDe8J

Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report

Multiple thoracic imaging modalities have been developed to link structure to function in the diagnosis and monitoring of lung disease. Volumetric computed tomography (CT) renders three-dimensional maps of lung structures and may be combined with positron emission tomography (PET) to obtain dynamic physiological data. Magnetic resonance imaging (MRI) using ultrashort-echo time (UTE) sequences has improved signal detection from lung parenchyma; contrast agents are used to deduce airway function, ventilation-perfusion-diffusion, and mechanics. Proton MRI can measure regional ventilation-perfusion ratio. Quantitative imaging (QI)-derived endpoints have been developed to identify structure-function phenotypes, including air-blood-tissue volume partition, bronchovascular remodeling, emphysema, fibrosis, and textural patterns indicating architectural alteration. Coregistered landmarks on paired images obtained at different lung volumes are used to infer airway caliber, air trapping, gas and blood transport, compliance, and deformation. This document summarizes fundamental "good practice" stereological principles in QI study design and analysis; evaluates technical capabilities and limitations of common imaging modalities; and assesses major QI endpoints regarding underlying assumptions and limitations, ability to detect and stratify heterogeneous, overlapping pathophysiology, and monitor disease progression and therapeutic response, correlated with and complementary to, functional indices. The goal is to promote unbiased quantification and interpretation of in vivo imaging data, compare metrics obtained using different QI modalities to ensure accurate and reproducible metric derivation, and avoid misrepresentation of inferred physiological processes. The role of imaging-based computational modeling in advancing these goals is emphasized. Fundamental principles outlined herein are critical for all forms of QI irrespective of acquisition modality or disease entity.

Comparison of inspiratory and expiratory airway volumes and luminal areas among standing, sitting, and supine positions using upright and conventional CT

Upright computed tomography (CT) provides physiologically relevant images of daily life postures (sitting and standing). The volume of the human airway in sitting or standing positions remains unclear, and no clinical study to date has compared the inspiratory and expiratory airway volumes and luminal areas among standing, sitting, and supine positions. In this prospective study, 100 asymptomatic volunteers underwent both upright (sitting and standing positions) and conventional (supine position) CT during inspiration and expiration breath-holds and the pulmonary function test (PFT) within 2 h of CT. We compared the inspiratory/expiratory airway volumes and luminal areas on CT among the three positions and evaluated the correlation between airway volumes in each position on CT and PFT measurements. The inspiratory and expiratory airway volumes were significantly higher in the sitting and standing positions than in the supine position (inspiratory, 4.6% and 2.5% increase, respectively; expiratory, 14.9% and 13.4% increase, respectively; all P < 0.001). The inspiratory and expiratory luminal areas of the trachea, bilateral main bronchi, and average third-generation airway were significantly higher in the sitting and standing positions than in the supine position (inspiratory, 4.2‒10.3% increases, all P < 0.001; expiratory, 6.4‒12.8% increases, all P < 0.0001). These results could provide important clues regarding the pathogenesis of orthopnea. Spearman's correlation coefficients between the inspiratory airway volume on CT and forced vital capacity and forced expiratory volume in 1 s on PFT were numerically higher in the standing position than in the supine position (0.673 vs. 0.659 and 0.669 vs. 0.643, respectively); however, no statistically significant differences were found. Thus, the airway volumes on upright and conventional supine CT were moderately correlated with the PFT measurements.

Sex Differences in Airways at Chest CT: Results from the COPDGene Cohort

Background The prevalence of chronic obstructive pulmonary disease (COPD) in women is fast approaching that in men, and women experience greater symptom burden. Although sex differences in emphysema have been reported, differences in airways have not been systematically characterized. Purpose To evaluate whether structural differences in airways may underlie some of the sex differences in COPD prevalence and clinical outcomes. Materials and Methods In a secondary analyses of a multicenter study of never-, current-, and former-smokers enrolled from January 2008 to June 2011 and followed up longitudinally until November 2020, airway disease on CT images was quantified using seven metrics: airway wall thickness, wall area percent, and square root of the wall thickness of a hypothetical airway with internal perimeter of 10 mm (referred to as Pi10) for airway wall; and lumen diameter, airway volume, total airway count, and airway fractal dimension for airway lumen. Least-squares mean values for each airway metric were calculated and adjusted for age, height, ethnicity, body mass index, pack-years of smoking, current smoking status, total lung capacity, display field of view, and scanner type. In ever-smokers, associations were tested between each airway metric and postbronchodilator forced expiratory volume in 1 second (FEV1)-to-forced vital capacity (FVC) ratio, modified Medical Research Council dyspnea scale, St George's Respiratory Questionnaire score, and 6-minute walk distance. Multivariable Cox proportional hazards models were created to evaluate the sex-specific association between each airway metric and mortality. Results In never-smokers (n = 420), men had thicker airway walls than women as quantified on CT images for segmental airway wall area percentage (least-squares mean, 47.68 ± 0.61 [standard error] vs 45.78 ± 0.55; difference, -1.90; P = .02), whereas airway lumen dimensions were lower in women than men after accounting for height and total lung capacity (segmental lumen diameter, 8.05 mm ± 0.14 vs 9.05 mm ± 0.16; difference, -1.00 mm; P < .001). In ever-smokers (n = 9363), men had greater segmental airway wall area percentage (least-squares mean, 52.19 ± 0.16 vs 48.89 ± 0.18; difference, -3.30; P < .001), whereas women had narrower segmental lumen diameter (7.80 mm ± 0.05 vs 8.69 mm ± 0.04; difference, -0.89; P < .001). A unit change in each of the airway metrics (higher wall or lower lumen measure) resulted in lower FEV1-to-FVC ratio, more dyspnea, poorer respiratory quality of life, lower 6-minute walk distance, and worse survival in women compared with men (all P < .01). Conclusion Airway lumen sizes quantified at chest CT were smaller in women than in men after accounting for height and lung size, and these lower baseline values in women conferred lower reserves against respiratory morbidity and mortality for equivalent changes compared with men. © RSNA, 2022 Online supplemental material is available for this article.

CT-Based Commercial Software Applications: Improving Patient Care Through Accurate COPD Subtyping

Chronic obstructive pulmonary disease (COPD) is heterogenous in its clinical manifestations and disease progression. Patients often have disease courses that are difficult to predict with readily available data, such as lung function testing. The ability to better classify COPD into well-defined groups will allow researchers and clinicians to tailor novel therapies, monitor their effects, and improve patient-centered outcomes. Different modalities of assessing these COPD phenotypes are actively being studied, and an area of great promise includes the use of quantitative computed tomography (QCT) techniques focused on key features such as airway anatomy, lung density, and vascular morphology. Over the last few decades, companies around the world have commercialized automated CT software packages that have proven immensely useful in these endeavors. This article reviews the key features of several commercial platforms, including the technologies they are based on, the metrics they can generate, and their clinical correlations and applications. While such tools are increasingly being used in research and clinical settings, they have yet to be consistently adopted for diagnostic work-up and treatment planning, and their full potential remains to be explored.

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.

Oral Positive Expiratory Pressure Device for Excessive Dynamic Airway Collapse Caused by Emphysema

Excessive dynamic airway collapse (EDAC) contributes to breathlessness and reduced quality of life in individuals with emphysema. We tested a novel, portable, oral positive expiratory pressure (o-PEP) device in a patient with emphysema and EDAC. MRI revealed expiratory tracheal narrowing to 80 mm² that increased to 170 mm² with the o-PEP device. After 2-weeks use of the o-PEP device for 33% to 66% of activities, breathlessness, quality of life, and exertional dyspnea improved compared with minimal clinically important differences (MCID): University of California-San Diego Shortness of Breath questionnaire score declined 69 to 42 (MCID, ≥5), St. George's Respiratory Questionnaire score decreased 71 to 27 (MCID, ≥4), and before and after the 6-minute walk test Borg score difference improved from Δ3 to Δ2 (MCID, ≥1). During the 6-minute walk test on room air without the use of the o-PEP device, oxyhemoglobin saturation declined 91% to 83%; whereas, with the o-PEP device, the nadir was 90%. Use of the o-PEP device reduced expiratory central airway collapse and improved dyspnea, quality of life, and exertional desaturation in a patient with EDAC and emphysema.

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

Expiratory central airway collapse and symptoms in smokers

BACKGROUND

The prevalence and clinical impacts of expiratory central airway collapse (ECAC) in smokers remain controversial. Although studies have shown associations of ECAC with airflow limitation and symptoms, others have shown that higher tracheal collapsibility is associated with lower expiratory-to-inspiratory ratio of lung volume (E/I-LV), but not airflow limitation. This study tested whether ECAC of the trachea and main bronchi could occur exclusively in smokers with lower E/I-LV and affect their symptoms independent of emphysema and intrapulmonary airway disease.

METHODS

ECAC was defined as the expiratory-to-inspiratory ratio of cross-sectional lumen area <0.5 for at least one of the three locations, including the trachea, right and left main bronchi on static full-inspiratory, and end-tidal expiratory CT. Symptoms were assessed using the chronic obstructive pulmonary disease (COPD) assessment test (CAT) and modified MRC scale (mMRC).

RESULTS

Out of 241 smokers with and without COPD (n = 189 and 52, respectively), ECAC was found in 21 (9%) smokers. No ECAC was found in smokers with E/I-LV ≥0.75. CAT and mMRC in smokers with ECAC were higher than in non-ECAC smokers with E/I-LV <0.75, but comparable to those in non-ECAC smokers with E/I-LV ≥0.75. In the multivariable analysis of smokers with E/I-LV <0.75, ECAC was associated with increased mMRC and CAT independent of CT-emphysema severity, wall area percent of segmental airways, and forced expiratory volume in 1 s CONCLUSIONS: ECAC is associated with worsening of symptoms independent of emphysema and segmental airway disease in smokers with a lower expiratory-to-inspiratory lung volume ratio.

Differences in airway lumen area between supine and upright computed tomography in patients with chronic obstructive pulmonary disease

BACKGROUND

No clinical studies to date have compared the inspiratory and expiratory airway lumen area between supine and standing positions. Thus, the aims of this study were twofold: (1) to compare inspiratory and expiratory airway lumen area (IAA and EAA, respectively) on computed tomography (CT) among supine and standing positions; and (2) to investigate if IAA and EAA are associated with lung function abnormality in patients with chronic obstructive pulmonary disease (COPD).

METHODS

Forty-eight patients with COPD underwent both low-dose conventional (supine position) and upright CT (standing position) during inspiration and expiration breath-holds and a pulmonary function test (PFT) on the same day. We measured the IAA and EAA in each position.

RESULTS

For the trachea to the third-generation bronchi, the IAA was significantly larger in the standing position than in the supine position (4.1-4.9% increase, all p < 0.05). The EAA of all bronchi was significantly larger in the standing position than in the supine position (9.7-62.5% increases, all p < 0.001). The correlation coefficients of IAA in the standing position and forced expiratory volume in 1 s were slightly higher than those in the supine position. The correlation coefficients of EAA or EAA/IAA in the standing position and residual volume, and the inspiratory capacity/total lung capacity ratio were higher than those in the supine position.

CONCLUSIONS

Airway lumen areas were larger in the standing position than in the supine position. IAAs reflect airway obstruction, and EAAs reflect lung hyperinflation. Upright CT might reveal these abnormalities more precisely. Trial registration University Hospital Medical Information Network (UMIN 000026587), Registered 17 March 2017. URL: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000030456 .

Comparative effects of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers on pulmonary function in hypertensive patients

OBJECTIVES

Hypertension is a very common cardiovascular disease. Angiotensin-converting enzyme inhibitors (ACEi) and angiotensin II receptor blockers (ARBs) are widely used to treat hypertension. Many patients with hypertension are vulnerable to the antihypertensive adverse effects, which potentially reduces the adherence rate. Therefore, we conducted this study in order to evaluate the safety profile of both classes (ACEi and ARBs) on respiratory functions.

METHODS

Two main groups of subjects were studied: first group is healthy control subjects and the second group is hypertensive patients, which was subdivided into subgroups in order to investigate the effect of all tested medications (captopril, enalapril, lisinopril, losartan, and valsartan). Respiratory efficiency was evaluated by measuring pulmonary function tests: FEV1, FVC, and FEV1%. Measurements were done using micromedical spirometer.

RESULTS

We found that ARBs do not impair normal respiratory functions as measured by FEV1, FEV1%, and FVC in hypertensive patients. While ACEi treatments significantly reduced FEV1, FEV1%, and FVC compared to the other groups.

CONCLUSIONS

ARBs are not associated with any harmful effects on respiratory functions in hypertensive patients, unlike ACEi. As such, they could represent a first-choice treatment for hypertensive patients who are at high risk to the respiratory adverse effects.

Quality of life outcomes in tracheobronchomalacia surgery

Tracheobronchomalacia (TBM) is an obstructive airway disease characterized by laxity and redundancy of the posterior membrane of the main airways leading to dynamic airway collapse during exhalation. The gold standard for diagnosis is dynamic computed tomography (DCT) scan and dynamic flexible bronchoscopy (DFB). Patients with complete or near-complete collapse (>90% reduction in cross-sectional area) of the airway are possible candidates for surgical management. Central airway stabilization by tracheobronchoplasty (TBP) effectively corrects malacic airways and has demonstrated significant improvement in objective functional measures, which is often but not uniformly accompanied by equal improvement in health-related quality of life (HRQOL) metrics. This article reviews HRQOL instruments used to report outcomes after TBM surgery.

Expiratory central airway collapse - an overlooked entity?: Two case reports

INTRODUCTION

Expiratory central airway collapse is defined by excessive inward bulging of either tracheobronchial posterior membrane or cartilage. The former is called excessive dynamic airway collapse (EDAC), and the latter, depending on the site of collapse, tracheomalacia, bronchomalacia or tracheobronchomalacia. Due to their non-specific symptoms and lack of awareness amongst clinicians they tend to be mislabeled as common obstructive lung disorders, or complicate their course undetected. Particular controversies refer to EDAC sometimes considered just as a symptom of obstructive lung disease and not a separate entity. Nonetheless, a growing body of evidence indicates that EDAC might be present in patients without apparent obstructive lung disease or it might be an independent risk factor in chronic obstructive pulmonary disease or asthma patients.

PATIENT CONCERNS

Patient #1 was admitted because of idiopathic chronic cough whereas patient #2 was admitted for differential diagnosis of dyspnea of uncertain etiology. In both patients symptoms were unresponsive to bronchodilators and inhaled corticosteroids.

FINDINGS AND DIAGNOSIS

In both patients an excess collapse of tracheobronchial posterior membrane was detected during bronchoscopy; in patient #1, of right main bronchus and right upper lobe bronchus and in patient #2 of right upper lobe bronchus and both main bronchi. Excess central airway collapse in patient #2 was also visualized on expiratory chest CT. In patient #1 spirometry did not reveal obturation, whereas in patient #2 only mild, irreversible, obstruction was revealed, disproportionate to patients significant breathlessness.

INTERVENTIONS

Both patients were treated with N-acetylcysteine and adjustable positive expiratory pressure valves.

OUTCOMES

Due to aforementioned treatment chronic cough in patient #1 subsided almost completely whereas patient's #2 dyspnea improved significantly.

CONCLUSIONS

In presented cases EDAC was an unexpected finding, even though, it firmly corresponded with reported symptoms. Treatment modification led to improvement of patients quality of life.

Comparison of inspiratory and expiratory lung and lobe volumes among supine, standing, and sitting positions using conventional and upright CT

Currently, no clinical studies have compared the inspiratory and expiratory volumes of unilateral lung or of each lobe among supine, standing, and sitting positions. In this prospective study, 100 asymptomatic volunteers underwent both low-radiation-dose conventional (supine position, with arms raised) and upright computed tomography (CT) (standing and sitting positions, with arms down) during inspiration and expiration breath-holds and pulmonary function test (PFT) on the same day. We compared the inspiratory/expiratory lung/lobe volumes on CT in the three positions. The inspiratory and expiratory bilateral upper and lower lobe and lung volumes were significantly higher in the standing/sitting positions than in the supine position (5.3–14.7% increases, all P < 0.001). However, the inspiratory right middle lobe volume remained similar in the three positions (all P > 0.15); the expiratory right middle lobe volume was significantly lower in the standing/sitting positions (16.3/14.1% decrease) than in the supine position (both P < 0.0001). The Pearson’s correlation coefficients (r) used to compare the total lung volumes on inspiratory CT in the supine/standing/sitting positions and the total lung capacity on PFT were 0.83/0.93/0.95, respectively. The r values comparing the total lung volumes on expiratory CT in the supine/standing/sitting positions and the functional residual capacity on PFT were 0.83/0.85/0.82, respectively. The r values comparing the total lung volume changes from expiration to inspiration on CT in the supine/standing/sitting positions and the inspiratory capacity on PFT were 0.53/0.62/0.65, respectively. The study results could impact preoperative CT volumetry of the lung in lung cancer patients (before lobectomy) for the prediction of postoperative residual pulmonary function, and could be used as the basis for elucidating undetermined pathological mechanisms. Furthermore, in addition to morphological evaluation of the chest, inspiratory and expiratory upright CT may be used as an alternative tool to predict lung volumes such as total lung capacity, functional residual capacity, and inspiratory capacity in situation in which PFT cannot be performed such as during an infectious disease pandemic, with relatively more accurate predictability compared with conventional supine CT.

Chronic Obstructive Pulmonary Disease in Women: A Biologically Focused Review with a Systematic Search Strategy

Purpose

Evidence suggests that chronic obstructive pulmonary disease (COPD) symptoms and progression may differ between men and women. However, limited information is currently available on the pathophysiological and biological factors that may underlie these sex-related differences. The objective of this review is to systematically evaluate reports of potential sex-related differences, including genetic, pathophysiological, structural, and other biological factors, that may influence COPD development, manifestation, and progression in women.

Patients and Methods

A PubMed literature search was conducted from inception until January 2020. Original reports of genetic, hormonal, and physiological differences, and biological influences that could contribute to COPD development, manifestation, and progression in women were included.

Results

Overall, 491 articles were screened; 29 articles met the inclusion criteria. Results from this analysis demonstrated between-sex differences in inflammatory, immune, genetic, structural, and physiological factors in patients with COPD.

Conclusion

Various biological differences are observed between men and women with COPD including differences in inflammatory and metabolic pathways related to obesity and fat distribution, immune cell function and autophagy, extent and distribution of emphysema and airway wall remodeling. An enhanced understanding of these differences has the potential to broaden our understanding of how COPD develops and progresses, thereby providing an opportunity to ultimately improve diagnosis, treatment, and monitoring of COPD in both men and women.

Biomarkers for chronic obstructive pulmonary disease diagnosis and progression: insights, disappointments and promise

PURPOSE OF REVIEW

This article reviews the status of biomarkers useful in the diagnosis and progression of chronic obstructive pulmonary disease (COPD). Biomarkers have been the focus of a great deal of COPD-related research in recent years, although useful markers in these specific arenas remain elusive.

RECENT FINDINGS

No biomarker other than lung function has been shown to be useful, to date, for the diagnosis of COPD. The best blood-based biomarkers for the progression of COPD may involve combinations of individual markers, such as CC16, fibrinogen and sRAGE. New imaging metrics, such as central airway collapse, pulmonary vascular changes and central airway branch variation, may be able to provide valuable prognostic and information, although these remain confined to research applications.

SUMMARY

Blood-based biomarkers for diagnosing and determining the progression of COPD remain disappointingly elusive. Although there have been some advances in nonblood-based markers, such as those from imaging, exhaled breath or physiologic assessment, these remain limited, for the most part, to research applications. Moving toward better markers that could be used in clinical application in the screening and diagnosis of COPD that could also provide prognostic information remains an important goal of research.

Fifty Years of Progress in the Epidemiology of Chronic Obstructive Pulmonary Disease: A Review of National Heart, Lung, and Blood Institute-Sponsored Studies

Our understanding of the epidemiology of chronic obstructive pulmonary disease (COPD), including such metrics as incidence, prevalence, risk factors, outcome, and comorbidities has increased greatly over the past 50 years. Much of this increase is attributable to National Heart Blood and Lung Institute (NHLBI)-sponsored studies. This paper will review 13 of these key studies and their contribution to our understanding of COPD in the last half century.

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).

Recent Advances in Computed Tomography Imaging in Chronic Obstructive Pulmonary Disease

Lung imaging is increasingly being used to diagnose, quantify, and phenotype chronic obstructive pulmonary disease (COPD). Although spirometry is the gold standard for the diagnosis of COPD and for severity staging, the role of computed tomography (CT) imaging has expanded in both clinical practice and research. COPD is a heterogeneous disease with considerable variability in clinical features, radiographic disease, progression, and outcomes. Recent studies have examined the utility of CT imaging in enhancing diagnostic certainty, improving phenotyping, predicting disease progression and prognostication, selecting patients for intervention, and also in furthering our understanding of the complex pathophysiology of this disease. Multiple CT metrics show promise for use as imaging biomarkers in COPD.

Ultralow Dose Dynamic Expiratory Computed Tomography for Evaluation of Tracheomalacia

OBJECTIVE

The aim of this study was to determine the average effective radiation dose and feasibility of ultralow dose dynamic expiratory computed tomography (CT) for evaluation of tracheomalacia (ULD) and to evaluate factors that impact image quality.

METHODS

This is a retrospective study of 64 consecutive patients from September to October 2016 for the evaluation of tracheomalacia. All studies were performed with routine inspiration chest CT followed by ULD z(kilovoltage peak (kVp) 80, 100, or 120 and fixed milliamperage 10) or typical dose CT (TD) (kVp 100 or 120 with automated milliamperage) dynamic expiration CT. Image quality was considered diagnostic if the trachea area could be accurately measured for tracheomalacia assessment, and diagnostic studies were graded fair, good, or excellent. Scan length, image quality, and effective radiation dose were compared for ULD versus TD and ULD at 100 kVp versus ULD at 80 kVp. For ULD studies, patient factors were compared across image quality.

RESULTS

The ULD had a mean effective radiation dose of 0.08 mSv, with all studies of diagnostic image quality. The ULD showed 95% reduction in effective radiation dose (P < 0.001), 14% significant reduction in scan length (P = 0.029), and qualitatively decreased image quality compared w2 ith TD (P < 0.001). The ULD at 100 kVp had significantly better image quality compared with ULD at 80 kVp (P = 0.041) with higher effective radiation dose (0.09 vs 0.05 mSv) (P < 0.001). Body mass index significantly impacted image quality for all ULD studies but not for ULD at 80 or 100 kVp.

CONCLUSION

For evaluation of tracheomalacia, ULD showed low effective radiation dose less than 0.1 mSv and maintained diagnostic image quality.

Respiratory symptoms in smokers with normal spirometry: clinical significance and management considerations

PURPOSE OF REVIEW

Current respiratory society guidelines recommend confirming the diagnosis of chronic obstructive pulmonary disease (COPD) with demonstration of airflow obstruction on spirometry. However, multiple recent studies have demonstrated that smokers without overt airflow obstruction on spirometry, termed symptomatic smokers, have evidence of structural lung disease on imaging, have a substantial symptom burden, and also suffer respiratory exacerbations. In this review, we provide an overview of the epidemiology of symptomatic smokers, and address issues of screening and diagnosis, evaluation, and management considerations.

RECENT FINDINGS

Two large prospective cohorts of adults with and at risk for COPD quantified the respiratory morbidity of symptomatic smokers. These studies demonstrated that approximately half of smokers without spirometrically defined airflow obstruction have increased respiratory symptoms, poor quality of life, low functional capacity, and suffer from respiratory exacerbations. Symptomatic smokers also have evidence of structural lung disease on imaging, and are at risk for faster lung function decline compared with those without respiratory symptoms. Several methods have been proposed to detect smoking-related lung damage among symptomatic smokers with normal forced expired volume in 1 second (FEV1)/forced vital capacity (FVC) ratio. Novel spirometry measures have been reported to diagnose disease before detection using traditional spirometry thresholds. Small airway involvement can be detected earlier using impulse oscillometry and metrics on multiple breath nitrogen washout tests. Imaging biomarkers have been developed that are associated with respiratory morbidity and lung function decline in symptomatic smokers. The translation of novel methods for COPD disease detection into more timely introduction of therapeutics and a consequent reduction in long-term morbidity and mortality has not yet been observed.

SUMMARY

A better understanding of the pathobiologic basis of disease in smokers without overt airflow limitation, and earlier recognition of lung disease, while also appropriately evaluating for comorbidities that may account for the symptoms, will enhance the management of symptomatic smokers with preserved lung function.

Imaging Advances in Chronic Obstructive Pulmonary Disease. Insights from the Genetic Epidemiology of Chronic Obstructive Pulmonary Disease (COPDGene) Study

The Genetic Epidemiology of Chronic Obstructive Pulmonary Disease (COPDGene) study, which began in 2007, is an ongoing multicenter observational cohort study of more than 10,000 current and former smokers. The study is aimed at understanding the etiology, progression, and heterogeneity of chronic obstructive pulmonary disease (COPD). In addition to genetic analysis, the participants have been extensively characterized by clinical questionnaires, spirometry, volumetric inspiratory and expiratory computed tomography, and longitudinal follow-up, including follow-up computed tomography at 5 years after enrollment. The purpose of this state-of-the-art review is to summarize the major advances in our understanding of COPD resulting from the imaging findings in the COPDGene study. Imaging features that are associated with adverse clinical outcomes include early interstitial lung abnormalities, visual presence and pattern of emphysema, the ratio of pulmonary artery to ascending aortic diameter, quantitative evaluation of emphysema, airway wall thickness, and expiratory gas trapping. COPD is characterized by the early involvement of the small conducting airways, and the addition of expiratory scans has enabled measurement of small airway disease. Computational advances have enabled indirect measurement of nonemphysematous gas trapping. These metrics have provided insights into the pathogenesis and prognosis of COPD and have aided early identification of disease. Important quantifiable extrapulmonary findings include coronary artery calcification, cardiac morphology, intrathoracic and extrathoracic fat, and osteoporosis. Current active research includes identification of novel quantitative measures for emphysema and airway disease, evaluation of dose reduction techniques, and use of deep learning for phenotyping COPD.

Tracheal collapsibility in adults is dynamic over time

BACKGROUND

Tracheal collapse is a weakness of the tracheal wall leading to expiratory central airway collapse of more than 50% compared to inspiration. It has previously been discussed whether the collapsibility of the greater airways is a stable or a dynamic condition. Indeed, other well-known lung diseases such as asthma are characterized by dynamic changes with respect to pulmonary function indices. There are several different morphologies of the trachea related to collapsibility such as the crescent type and the saber-sheath type both involving the tracheal cartilage and excess dynamic airway collapse only involving the posterior membranous part of the trachea. Is the morphology of the trachea important for the course of the disease? The effect or adverse effects of inhaled corticosteroids are thought to play a role in the increasing incidence of the excess tracheal collapse. In this pilot study, we hypothesized that the excess collapsibility of the tracheal wall is dynamic.

METHODS

We prospectively examined 20 patients with excessive tracheal collapse on previous CT scans performed primarily due to bronchiectasis. A repeat CT scan was performed in order to evaluate the collapsibility. Before the repeat scan, patients were trained in maximal inspiration, expiration and breathholding. CT was performed in full inspiration and at end-expiration. Image assessment was performed on a dedicated CT workstation using standard lung window display settings. The percentage expiratory collapse based on cross sectional areas from carina to the thoracic inlet was calculated. Pulmonary function tests were performed and analysed in accordance with the American Thoracic Society and the European Respiratory Society guidelines.

RESULTS

Repeat CT scan were performed after 24 month +/- 7.2. Six of the 20 participants (30%) were males. Mean age was 67 +/- 11.3 years. Mean FEV1 was 83% of predicted, FVC 96.6 % of predicted and FEV1/FVC-ratio 71%. In 45% of the patients tracheal expiratory collapse improved (by more than 10%) based on percentage change in cross sectional areas in expiration compared to inspiration. 35% of patients showed disease progression with increased collapse and in 20% the collapsibility remained unchanged.

CONCLUSION

We demonstrate that the collapsibility in a large fraction of the patients had actually improved at the follow up examination. We do not find any dependency of the change in collapsibility on the morphology of the trachea after end expiration, use of corticosteroid, or recurrent infections. In addition, no correlation between the changes in collapse and changes in the pulmonary function tests and the symptoms is observed.