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

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.

Chronic respiratory symptoms following deployment-related occupational and environmental exposures among US veterans

OBJECTIVES

Characterise inhalational exposures during deployment to Afghanistan and Southwest Asia and associations with postdeployment respiratory symptoms.

METHODS

Participants (n=1960) in this cross-sectional study of US Veterans (Veterans Affairs Cooperative Study 'Service and Health Among Deployed Veterans') completed an interviewer-administered questionnaire regarding 32 deployment exposures, grouped a priori into six categories: burn pit smoke; other combustion sources; engine exhaust; mechanical and desert dusts; toxicants; and military job-related vapours gas, dusts or fumes (VGDF). Responses were scored ordinally (0, 1, 2) according to exposure frequency. Factor analysis supported item reduction and category consolidation yielding 28 exposure items in 5 categories. Generalised linear models with a logit link tested associations with symptoms (by respiratory health questionnaire) adjusting for other covariates. OR were scaled per 20-point score increment (normalised maximum=100).

RESULTS

The cohort mean age was 40.7 years with a median deployment duration of 11.7 months. Heavy exposures to multiple inhalational exposures were commonly reported, including burn pit smoke (72.7%) and VGDF (72.0%). The prevalence of dyspnoea, chronic bronchitis and wheeze in the past 12 months was 7.3%, 8.2% and 15.6%, respectively. Burn pit smoke exposure was associated with dyspnoea (OR 1.22; 95% CI 1.06 to 1.47) and chronic bronchitis (OR 1.22; 95% CI 1.13 to 1.44). Exposure to VGDF was associated with dyspnoea (OR 1.29; 95% CI 1.14 to 1.58) and wheeze (OR 1.18; 95% CI 1.02 to 1.35).

CONCLUSION

Exposures to burn pit smoke and military occupational VGDF during deployment were associated with an increased odds of chronic respiratory symptoms among US Veterans.

Dysanapsis is differentially related to lung function trajectories with distinct structural and functional patterns in COPD and variable risk for adverse outcomes

Background

Abnormal lung function trajectories are associated with increased risk of chronic obstructive pulmonary disease (COPD) and premature mortality; several risk factors for following these trajectories have been identified. Airway under-sizing dysanapsis (small airway lumens relative to lung size), is associated with an increased risk for COPD. The relationship between dysanapsis and lung function trajectories at risk for adverse outcomes of COPD is largely unexplored. We test the hypothesis that dysanapsis differentially affects distinct lung function trajectories associated with adverse outcomes of COPD.

Methods

To identify lung function trajectories, we applied Bayesian trajectory analysis to longitudinal FEV1 and FVC Z-scores in the COPDGene Study, an ongoing longitudinal study that collected baseline data from 2007 to 2012. To ensure clinical relevance, we selected trajectories based on risk stratification for all-cause mortality and prospective exacerbations of COPD (ECOPD). Dysanapsis was measured in baseline COPDGene CT scans as the airway lumen-to-lung volume (a/l) ratio. We compared a/l ratios between trajectories and evaluated their association with trajectory assignment, controlling for previously identified risk factors. We also assigned COPDGene participants for whom only baseline data is available to their most likely trajectory and repeated our analysis to further evaluate the relationship between trajectory assignment and a/l ratio measures.

Findings

We identified seven trajectories: supranormal, reference, and five trajectories at increased risk for mortality and exacerbations. Three at-risk trajectories are characterized by varying degrees of concomitant FEV1 and FVC impairments and exhibit airway predominant COPD patterns as assessed by quantitative CT imaging. These trajectories have lower a/l ratio values and increased risk for mortality and ECOPD compared to the reference trajectory. Two at-risk trajectories are characterized by disparate levels of FEV1 and FVC impairment and exhibit mixed airway and emphysema COPD patterns on quantitative CT imaging. These trajectories have markedly lower a/l ratio values compared to both the reference trajectory and airway-predominant trajectories and are at greater risk for mortality and ECOPD compared to the airway-predominant trajectories. These findings were observed among the participants with baseline-only data as well.

Interpretation

The degree of dysanapsis appears to portend patterns of progression leading to COPD. Assignment of individuals-including those without spirometric obstruction-to distinct trajectories is possible in a clinical setting and may influence management strategies. Strategies that combine CT-assessed dysanapsis together with spirometric measures of lung function and smoke exposure assessment are likely to further improve trajectory assignment accuracy, thereby improving early detection of those most at risk for adverse outcomes.

Funding

United States National Institute of Health, COPD Foundation, and Brigham and Women's Hospital.

[Epidemiology and hospitalization costs analysis of female inpatients with acute exacerbation of chronic obstructive pulmonary disease in Beijing from 2013 to 2020]

OBJECTIVE

To study epidemiological characteristics and hospitalization costs of female inpatients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) in Beijing.

METHODS

A retrospective study was conducted to analyze electronic hospitalization summary reports of female inpatients with AECOPD in Beijing from 2013 to 2020. Clinical characteristics (age distribution and comorbidities), epidemiological characteristics (temporal and spatial distribution characteristics), hospi-talization times and costs of patients were described.

RESULTS

A total of 57 911 subjects in 166 hospitals were included in this study, with a mean age of (78.84±8.59) years and the highest number of patients aged 80-89 years (49.06%), followed by patients aged 70-79 years (31.08%), and the lowest number of patients under 50 years (0.41%). The proportions of patients with coronary heart disease, hypertension and heart failure were 30.60%, 30.52% and 26.54% respectively. The median number of daily hospitalizations during the study period was 18 (IQR: 16). The number of daily hospitalizations for AECOPD showed an overall growth trend over the eight years from 2013 to 2020, starting to increase significantly in 2015 and continuing to increase until 2019, then followed by a decline in 2020. The proportion of inpatient admissions was higher in winter and spring (54.09%) than that in summer and autumn (45.91%). The top three districts in terms of the proportion of total inpatient admissions were Xicheng district (14.18%), Chaoyang district (14.12%) and Fengtai district (13.47%). The density of inpatients was relatively high in the western regions, central urban areas and northeastern regions of the city, while the density of inpatients was relatively low in the near suburbs. The median number of hospital days for female patients with AECOPD was 12 days, and the median hospital costs was CNY 20 648.37. Patients from urban areas had longer hospitalization times and higher hospitalization costs than those from suburban areas (P < 0.001). Western medicine expenses accounted for the largest proportion of total hospital expenses (33.32%). During the study period, hospitalization costs exhibited an overall pattern of initial growth, followed by subsequent decline, eventually stabilizing. The differences in hospitalization costs among the patients with different comorbidities were significant.

CONCLUSION

Female hospitalized patients with AECOPD in Beijing were older than 70 years, often complicated by cardiovascular disease. AECOPD occurred mainly in winter and spring, with regional differences. The hospitalization costs were closely associated with the patients' age, comorbidities, and the geographicical region.

Quantitative assessment of airway wall thickness in COPD patients with interstitial lung abnormalities

Background

Whether the airway is involved in the pathogenesis of interstitial lung abnormalities (ILA) is not well understood. Also the impact of ILA on lung function in COPD patients remains controversial. We aimed to assess the quantitative CT measurements of airway wall thickness (AWT) and lung function according to ILA status in COPD patients.

Methods

157 COPD patients discharged from our hospital from August 1, 2019 through August 31, 2022 who underwent chest CT imagings and pulmonary function tests were retrospectively enrolled. Linear regression analysis and multiple models were used to analyze associations between quantitative assessment of airway wall changes and the presence of ILA.

Results

In 157 COPD patients, 23 patients (14.6%) had equivocal ILA, 42 patients (26.8%) had definite ILA. The definite ILA group had the highest measurements of Pi10 (square root of theoretical airway wall area with a lumen perimeter of 10 mm), segmental AWT and segmental WA% (percentage of wall area), whereas the no ILA group had the lowest measurements of Pi10, segmental AWT and segmental WA%. In the adjusted analyses (adjusted by age, sex, body mass index, smoking intensity, COPD GOLD stage, lung function, slice thickness and scanner type), compared to COPD patients without ILA, the measurements of Pi10, segmental AWT and segmental WA% were higher in definite ILA group with differences of 0.225 mm (p = 0.012), 0.152 mm (p < 0.001), 4.8% (p < 0.001) respectively. COPD patients with definite ILA tended to have higher FEV1% predicted, FVC% predicted and lower MMEF75/25% predicted, but there were no statistically differences among the three groups.

Conclusion

Our study demonstrates the higher AWT measures in COPD patients with ILA compared to the patients without ILA. These findings suggest that the airway may be involved in the pathogenesis of ILA.

Cigarette smoking and disproportionate changes of thoracic skeletal muscles in low-dose chest computed tomography

Association between smoking intensity and the quantity and quality of thoracic skeletal muscles (TSMs) remains unexplored. Skeletal muscle index (SMI; skeletal muscle area/height2) and percentage of normal attenuation muscle area (NAMA%) were measured to represent the quantity and quality of the skeletal muscles, respectively, and quantification was performed in pectoralis muscle at aortic arch (AA-PM), TSM at carina (C-TSM), erector spinae muscle at T12 (T12-ESM), and skeletal muscle at L1 (L1-SM). Among the 258 men (median age, 62 years [IQR: 58-69]), 183 were current smokers (median smoking intensity, 40 pack-years [IQR: 30-46]). SMI and NAMA% of AA-PM significantly decreased with pack-year (β =  - 0.028 and - 0.076; P < 0.001 and P = 0.021, respectively). Smoking intensity was inversely associated with NAMA% of C-TSM (β =  - 0.063; P = 0.001), whereas smoking intensity showed a borderline association with SMI of C-TSM (β =  - 0.023; P = 0.057). Smoking intensity was associated with the change in NAMA% of L1-SM (β =  - 0.040; P = 0.027), but was not associated with SMI of L1-SM (P > 0.05). Neither NAMA% nor SMI of T12-ESM was affected by smoking intensity (P > 0.05). In conclusion, smoking intensity was associated with the change of TSMs. Its association varied according to the location of TSMs, with the most associated parts being the upper (AA-PM) and middle TSMs (C-TSM).

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.

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.

Quantitative Analysis for Lung Disease on Thin-Section CT

Thin-section computed tomography (CT) is widely employed not only for assessing morphology but also for evaluating respiratory function. Three-dimensional images obtained from thin-section CT provide precise measurements of lung, airway, and vessel volumes. These volumetric indices are correlated with traditional pulmonary function tests (PFT). CT also generates lung histograms. The volume ratio of areas with low and high attenuation correlates with PFT results. These quantitative image analyses have been utilized to investigate the early stages and disease progression of diffuse lung diseases, leading to the development of novel concepts such as pre-chronic obstructive pulmonary disease (pre-COPD) and interstitial lung abnormalities. Quantitative analysis proved particularly valuable during the COVID-19 pandemic when clinical evaluations were limited. In this review, we introduce CT analysis methods and explore their clinical applications in the context of various lung diseases. We also highlight technological advances, including images with matrices of 1024 × 1024 and slice thicknesses of 0.25 mm, which enhance the accuracy of these analyses.

Defining and Promoting Pediatric Pulmonary Health: Assessing Lung Function and Structure

Lifelong respiratory health is rooted in the structural and functional development of the respiratory system in early life. Exposures and interventions antenatally through childhood can influence lung development into young adulthood, the life stage with the highest achievable lung function. Because early respiratory health sets the stage for adult lung function trajectories and risk of developing chronic obstructive pulmonary disease, understanding how to promote lung health in children will have far reaching personal and population benefits. To achieve this, it is critical to have accurate and precise measures of structural and functional lung development that track throughout life stages. From this foundation, evaluation of environmental, genetic, metabolic, and immune mechanisms involved in healthy lung development can be investigated. These goals require the involvement of general pediatricians, pediatric subspecialists, patients, and researchers to design and implement studies that are broadly generalizable and applicable to otherwise healthy and chronic disease populations. This National Institutes of Health workshop report details the key gaps and opportunities regarding lung function and structure.

Association of T cell infiltration and morphological change of thymus gland with the aggravation of pulmonary emphysema in testosterone deficiency

Chronic obstructive pulmonary disease is an inflammatory lung disease characterized by chronic bronchitis and emphysema. Our previous study revealed that testosterone depletion induced T cell infiltration in the lungs and aggravated pulmonary emphysema in orchiectomized (ORX) mice exposed to porcine pancreatic elastase (PPE). However, the association between T cell infiltration and emphysema remains unclear. The aim of this study was to determine whether thymus and T cells are involved in the exacerbation of PPE-induced emphysema in ORX mice. The weight of thymus gland in ORX mice was significantly greater than that of sham mice. The pretreatment of anti-CD3 antibody suppressed PPE-induced thymic enlargement and T cell infiltration in the lungs in ORX mice, resulting in improved expansion of the alveolar diameter, a marker of emphysema exacerbation. These results suggest that increased thymic function due to testosterone deficiency and the associated increased pulmonary infiltration of T cells may trigger the development of emphysema.

New Evidence of Microplastics in the Lower Respiratory Tract: Inhalation through Smoking

To investigate the relation of smoking and microplastic inhalation, we conducted a prospective study combining population-based and experimental work. Bronchoalveolar lavage fluid (BALF) samples from 17 smokers and 15 nonsmokers were collected in Zhuhai City, China. We simulated an active smoking model to explore the contribution of smoking to inhaled microplastics. The characteristics of microplastics in BALF samples and cigarette smoke were determined using laser direct infrared spectroscopy. We compared the differences between smokers and nonsmokers as well as between cigarette smoke and control groups. Microplastics were identified positive in all BALF samples. Smokers had higher concentrations of total microplastics (25.86 particles/g), polyurethane (11.34 particles/g), and silicone (1.15 particles/g) than nonsmokers. In the cigarette smoking simulation model, higher concentrations of total microplastics (9.99 particles/L), polyurethane (4.66 particles/L), and silicone (2.78 particles/L) were present in the cigarette smoke than those in the control group. We confirmed and extended the evidence on the presence of microplastics in the lower respiratory tract. These findings also provide new evidence on the relation between cigarette smoking and microplastic inhalation.

Association of age with computed tomography airway tree morphology in male and female never smokers without lung disease history

BACKGROUND

Sex and aging may affect the airway tree structure in patients with airway diseases and even healthy subjects. Using chest computed tomography (CT), this study sought to determine whether age is associated with airway morphological features differently in healthy males and females.

METHODS

This retrospective cross-sectional study consecutively incorporated lung cancer screening CT data of asymptomatic never smokers (n = 431) without lung disease history. Luminal areas were measured at the trachea, main bronchi, bronchus intermedius, segmental and subsegmental bronchus, and the ratio of their geometric mean to total lung volume (airway-to-lung size ratio, ALR) was determined. Airway fractal dimension (AFD) and total airway count (TAC) were calculated for the segmented airway tree resolved on CT.

RESULTS

The lumen areas of the trachea, main bronchi, segmental and subsegmental airways, AFD and TAC visible on CT were smaller in females (n = 220) than in males (n = 211) after adjusting for age, height, and body mass index, while ALR or count of the 1st to 5th generation airways did not differ. Furthermore, in males but not in females, older age was associated with larger lumen sizes of the main bronchi, segmental and subsegmental airways, and ALR. In contrast, neither male nor female had any associations between age and AFD or TAC on CT.

CONCLUSION

Older age was associated with larger lumen size of the relatively central airways and ALR exclusively in males. Aging may have a more profound effect on airway lumen tree caliber in males than in females.