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

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.

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.

Measuring pulmonary function in COPD using quantitative chest computed tomography analysis

COPD is diagnosed and evaluated by pulmonary function testing (PFT). Chest computed tomography (CT) primarily serves a descriptive role for diagnosis and severity evaluation. CT densitometry-based emphysema quantification and lobar fissure integrity assessment are most commonly used, mainly for lung volume reduction purposes and scientific efforts.

A shift towards a more quantitative role for CT to assess pulmonary function is a logical next step, since more, currently underutilised, information is present in CT images. For instance, lung volumes such as residual volume and total lung capacity can be extracted from CT; these are strongly correlated to lung volumes measured by PFT.

This review assesses the current evidence for use of quantitative CT as a proxy for PFT in COPD and discusses challenges in the movement towards CT as a more quantitative modality in COPD diagnosis and evaluation. To better understand the relevance of the traditional PFT measurements and the role CT might play in the replacement of these parameters, COPD pathology and traditional PFT measurements are discussed.

CT may be used as a proxy for lung function in COPD diagnosis and evaluation, particularly for the hyperinflation markershttps://bit.ly/2RrGAZf

Imbalance Between Injury and Defense in the COPD Emphysematous Phenotype

The chronic obstructive pulmonary disease (COPD) emphysematous phenotype is characterized by destruction of lung tissue structure. Patients with this phenotype usually present with typical emphysema-like changes on chest computed Tomography CT, experience higher mortality and poorer prognosis, and are insensitive to routine pharmacological COPD therapy. However, the pathogenesis for the COPD emphysematous phenotype remains unclear, resulting in diagnostic and therapeutic challenges. The imbalance between injury and defense mechanisms is essential in the progression of many pulmonary diseases. Thus, in this review, we focus on the pathogenesis of the COPD emphysematous phenotype and discuss the pathophysiological processes involved in disease progression, from the perspective of injury and defense imbalance.

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.

Correlation between Computed Tomographic Analysis and Pulmonary Function Measurements in Patients with Relapsing Polychondritis

BACKGROUND

Relapsing polychondritis (RP) is a rare systemic disease of unknown origin, with cartilaginous involvement in multiple organs. Airway involvement is the most important prognostic factor in RP.

OBJECTIVES

Spirometric measurements and minimum tracheal cross-sectional area (mtCSA) have been reported as useful to assess the degree of airway stenosis. Because the length and severity of tracheal involvement in RP can vary, mtCSA might not provide enough information to assess tracheal abnormalities. We introduced tracheal volume (TrV) as a new method to evaluate correlations between chest computed tomography (CT) measurements and pulmonary function tests, including impulse oscillometry (IOS).

METHOD

We analyzed chest CT images, spirometry, and IOS collected at our institution from April 2004 to March 2019. We calculated correlations between chest CT measurements using software (TrV, TrV/tracheal length [TrV/TL], and mtCSA) and pulmonary function parameters.

RESULTS

Twenty-five of 73 clinically diagnosed patients with RP were included. Spirometric findings showed moderate airway obstruction. Peak flow (PEF) was strongly correlated with mtCSA, TrV, and TrV/TL (ρ = 0.74, p < 0.001). FEV1 was significantly correlated with mtCSA (ρ = 0.56, p = 0.004), TrV (ρ = 0.52, p = 0.007), and TrV/TL (ρ = 0.53, p = 0.006). Whereas respiratory resistance at 5 Hz (R5) and 20 Hz (R20) and resonant frequencies (RFs) were significantly correlated with TrV (ρ = -0.46, p = 0.021; ρ = -0.46, p = 0.046; and ρ = -0.42, p = 0.037, respectively), IOS parameters and mtCSA were not.

CONCLUSIONS

In patients with RP, TrV and mtCSA were strongly correlated with spirometric measurements. Respiratory resistances assessed by IOS correlated only with TrV. This suggests TrV assessment reflects pulmonary function in patients with RP more appropriately than mtCSA.

Evaluation of intrathoracic tracheal narrowing in patients with obstructive ventilatory impairment using dynamic chest radiography: A preliminary study

PURPOSE

Dynamic chest radiography (DCR) can observe the dynamic structure of the chest using continuous pulse fluoroscopy irradiation. However, its usefulness remains largely undetermined. The purpose of this study was to examine the relationship between changes in tracheal diameter during deep breathing and obstructive ventilation disorders using DCR.

METHOD

Twelve participants with obstructive ventilatory impairment and 28 with normal pulmonary function underwent DCR during one cycle of deep inspiration and expiration. Three evaluators blinded to pulmonary function test results independently measured lateral diameters of the trachea in DCR images to determine whether there was a difference in the amount of change in tracheal diameter depending on the presence or absence of pulmonary dysfunction. Tracheal narrowing was defined as a decrease in the lateral tracheal diameter of more than 30 %. Participants were divided into a narrowing group and a non-narrowing group, and it was examined whether each group correlated with values of pulmonary function tests.

RESULTS

Tracheal diameter was significantly narrowed in subjects with obstructive ventilatory impairment compared to normal subjects (P <  0.01). When subjects were divided into narrowing (tracheal narrowing rate [TNr] = 41.5 ± 7.7 %, n = 9) and non-narrowing groups (TNr = 9.1 ± 7.0 %, n = 31, p < 0.01), FEV1%-G, and %V25 were significantly smaller in the narrowing group than in the non-narrowing group (p < 0.01).

CONCLUSIONS

Changes in tracheal diameter during deep breathing were easily evaluated using DCR. DCR may, therefore, be useful for evaluating obstructive ventilation disorders.

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.

Continuous quantitative measurement of the main bronchial dimensions and lung density in the lateral position by four-dimensional dynamic-ventilation CT in smokers and COPD patients

Purpose

The purpose of this study was to measure changes in lung density and airway dimension in smokers in the lateral position using four-dimensional dynamic-ventilation computed tomography (CT) during free breathing and to evaluate their correlations with spirometric values.

Materials and methods

Preoperative pleural adhesion assessments included dynamic-ventilation CT of 42 smokers (including 22 patients with COPD) in the lateral position, with the unoperated lung beneath (dependent lung). The scanned lungs' mean lung density (MLD) and the bilateral main bronchi's luminal areas (Ai) were measured automatically (13-18 continuous image frames, 0.35 seconds/frame). Calculations included cross-correlation coefficients (CCCs) between the MLD and Ai time curves, and correlations between the quantitative measurements and spirometric values were evaluated by using Spearman's rank coefficient.

Results

The ΔMLD_1.05 (from the peak inspiration frame to the third expiratory frame, 1.05 seconds later) in the nondependent lung negatively correlated with FEV₁/FVC (r=-0.417, P<0.01), suggesting that large expiratory movement of the nondependent lung would compensate limited expiratory movement of the dependent lung due to COPD. The ΔAi_1.05 negatively correlated with the FEV₁/FVC predicted in both the lungs (r=-0.465 and -0.311, P<0.05), suggesting that early expiratory collapses of the main bronchi indicate severe airflow limitation. The CCC correlated with FEV₁/FVC in the dependent lung (r=-0.474, P<0.01), suggesting that reduced synchrony between the proximal airway and lung occurs in patients with severe airflow limitation.

Conclusion

In COPD patients, in the lateral position, the following abnormal dynamic-ventilation CT findings are associated with airflow limitation: enhanced complementary ventilation in the nondependent lung, early expiratory airway collapses, and reduced synchrony between airway and lung movements in the dependent lung.

Hyperinflated lungs compress the heart during expiration in COPD patients: a new finding on dynamic-ventilation computed tomography

Purpose

The aims of this study were to evaluate dynamic changes in heart size during the respiratory cycle using four-dimensional computed tomography (CT) and to understand the relationship of these changes to airflow limitation in smokers.

Materials and methods

A total of 31 smokers, including 13 with COPD, underwent four-dimensional dynamic-ventilation CT during regular breathing. CT data were continuously reconstructed every 0.5 s, including maximum cross-sectional area (CSA) of the heart and mean lung density (MLD). Concordance between the cardiac CSA and MLD time curves was expressed by cross-correlation coefficients. The CT-based cardiothoracic ratio at inspiration and expiration was also calculated. Comparisons of the CT indices between COPD patients and non-COPD smokers were made using the Mann–Whitney test. Spearman rank correlation analysis was used to evaluate associations between CT indices and the forced expiratory volume in 1 s (FEV_1.0) relative to the forced vital capacity (FVC).

Results

Cardiac CSA at both inspiration and expiration was significantly smaller in COPD patients than in non-COPD smokers (P<0.05). The cross-correlation coefficient between cardiac CSA and MLD during expiration significantly correlated with FEV_1.0/FVC (ρ=0.63, P<0.001), suggesting that heart size decreases during expiration in COPD patients. The change in the cardiothoracic ratio between inspiration and expiration frames was significantly smaller in COPD patients than in non-COPD smokers (P<0.01).

Conclusion

Patients with COPD have smaller heart size on dynamic-ventilation CT than non-COPD smokers and have abnormal cardiac compression during expiration.

Role of inspiratory capacity on dyspnea evaluation in COPD with or without emphysematous lesions: a pilot study

Background

Since forced expiratory volume in 1 second (FEV₁) shows a weak correlation with patients’ symptoms in COPD, some volume parameters may better reflect the change in dyspnea symptoms after treatment. In this article, we investigated the role of inspiratory capacity (IC) on dyspnea evaluation among COPD patients with or without emphysematous lesions.

Methods

In this prospective study, 124 patients with stable COPD were recruited. During the baseline visit, patients performed pulmonary function tests and dyspnea evaluation using the modified Medical Research Council (mMRC) scale. Partial patients underwent quantitative computerized tomography scans under physicians’ recommendations, and emphysematous changes were assessed using the emphysema index (EI; low attenuation area [LAA]% −950). These subjects were then divided into the emphysema-predominant group (LAA% −950≥9.9%) and the non-emphysema-predominant group (LAA% −950<9.9%). After treatment for ~1 month, subjects returned for reevaluation of both pulmonary function parameters and dyspnea severity. Correlation analysis between the change in IC (ΔIC) and dyspnea (ΔmMRC) was performed.

Results

Correlation analysis revealed that ΔIC was negatively correlated with ΔmMRC (correlation coefficient [cc], −0.490, P<0.001) in the total study population, which was stronger than that between ΔFEV₁ and ΔmMRC (cc, −0.305, P=0.001). Patients with absolute ΔmMRC >1 were more likely to exhibit a marked increase in IC (≥300 mL) than those with absolute ΔmMRC ≤1 (74.36% versus 35.29%; odds ratio [OR], 5.317; P<0.001). In the emphysema-predominant group, only ΔIC strongly correlated with ΔmMRC (cc, −0.459, P=0.005), while ΔFEV₁ did not (P>0.05).

Conclusion

IC could serve as an effective complement to FEV₁ in COPD patients undergoing dyspnea evaluation after treatment. For COPD patients with predominant emphysematous lesions, an increase in IC is particularly more suitable for explaining dyspnea relief than FEV₁.

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

RATIONALE AND OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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