Airway to Lung Volume Ratio on CT is Associated with Pulmonary Function Transition from Obstructive to Restrictive Pattern in Obesity

Background: Obesity is associated with excessive airway collapse and reduced lung volume; it is unknown whether it affects airway-lung interactions. We sought to compare the airway tree to lung volume ratio, assessed by CT, in obese individuals with and without ventilation disorders.Methods: Participants underwent inspiratory chest CT and pulmonary function. The percentage ratio of the whole airway tree to lung volume, automatically segmented via deep learning, was defined as CT airway volume percent (AWV%). Total airway count (TAC), airway wall area percent (WA%), and other CT indexes were also measured. Results: We evaluated 88 participants including adolescents(age: 14-18, n= 12) and adults (age: 19-25, n= 17; age: 26-35, n= 39; age> 35, n= 20). Obese adolescents had higher forced vital capacity (FVC) (P = 0.001) and lower AWV% (P = 0.008) than obese adults (age >35). Among obese adults, participants with restrictive disorders had larger AWV% (P < 0.001) and those with obstructive disorders showed smaller AWV% (P < 0.001) compared to participants with normal ventilation. AWV% was positively correlated with age and forced expiratory volume in 1 second (FEV1)/FVC and adversely related to FVC (P< 0.05 for all), and in multivariate models, AWV% independently predicted FEV1/FVC (R2 = 0.49, P < 0.001) and FVC (R2 = 0.60, P < 0.001).Conclusion: Transitions in lung function patterns between obese adolescents and adults are associated with airway to lung ratios. The obesity-induced disproportion between the airway tree and lung volume may adversely affect and complicate lung ventilation.

Computed tomography total airway count predicts progression to COPD in at risk smokers

There is limited understanding of how to identify people at high risk of developing chronic obstructive pulmonary disease (COPD). Our objective was to investigate the association between computed tomography (CT) total airway count (TAC) and incident COPD over 3-years among ever-smokers from the population-based Canadian Cohort Obstructive Lung Disease (CanCOLD) study.CT and spirometry were acquired in ever-smokers at baseline; spirometry was repeated at 3-year follow-up. CT TAC was generated by summing all airway segments in the segmented airway tree (VIDA Diagnostics, Inc.). CT airway wall area, wall thickness for a theoretical airway with 10 mm perimeter (Pi10), and low attenuation areas below −856HU (LAA856) were also measured. Logistic and mixed effects regression models were constructed to determine the association for CT measurements with development of COPD and FEV1/FVC decline, respectively.Among 316 at risk participants evaluated at baseline (65±9 years, 40% female, 18±19 pack-years), incident COPD was detected in 56 participants (18%) over a median 3.1±0.6 years of follow-up. Among CT measurements, only TAC was associated with incident COPD (p=0.03), where a 1-sd decrement in TAC increased the odds ratio for incident COPD by a factor of two. In a multivariable linear regression model, reduced TAC was significantly associated with greater longitudinal FEV1/FVC decline (p=0.03), but no other measurements were significant.CT TAC predicts incident COPD in at risk smokers, indicating that smokers exhibit early structural changes associated with COPD prior to abnormal spirometry.

Computed tomography airway tree tortuosity features predict functional small airway disease in chronic obstructive pulmonary disease

Over 1 000 000 Canadians are diagnosed with Chronic Obstructive Pulmonary Disease (COPD) and by 2020 the disease will be the third deadliest on Earth. Despite high prevalence, diagnosis of COPD occurs late in the disease course, after a large portion of the small airways are destroyed. Current methods to quantify small airway disease (SAD) using the Disease Probability Measure (DPM) approach requires CT images acquired at full inspiration and full expiration, and therefore there are technical challenges and dose concerns Computed Tomography (CT) imaging using only a single full inspiration CT image can be used segment the central airway tree and generate quantitative morphometric measurements.

Computed tomography airway tree tortuosity features predict functional small airway disease in chronic obstructive pulmonary disease

Over 1 000 000 Canadians are diagnosed with Chronic Obstructive Pulmonary Disease (COPD) and by 2020 the disease will be the third deadliest on Earth. Despite high prevalence, diagnosis of COPD occurs late in the disease course, after a large portion of the small airways are destroyed. Current methods to quantify small airway disease (SAD) using the Disease Probability Measure (DPM) approach requires CT images acquired at full inspiration and full expiration, and therefore there are technical challenges and dose concerns Computed Tomography (CT) imaging using only a single full inspiration CT image can be used segment the central airway tree and generate quantitative morphometric measurements.

Airway Compliance Measurements in Mouse Models of Respiratory Diseases

The quantification of airway compliance (Caw) is essential to the study of airway alterations in disease models. However, the required measurements of airway pressure and volume are difficult to acquire in mice. We hypothesized that the inflation limb of full-range pressure-volume (PV) curves could be used to quantify Caw, as it contains a segment where only the airway tree is distended. The study objective was to assess the feasibility of the approach by analysis of full-range PV curves previously collected in three mouse models: an elastase model of emphysema, a genetic model spontaneously developing emphysema (leukotriene C4 synthase knock-out; LTC4S-KO) and a bleomycin model of lung fibrosis. Attempts to validate results included Caw change relative to respiratory system compliance (ΔCaw/ΔC), the minute work of breathing (mWOB) and the elastance at 20.5 Hz (Ers_20.5) from prior respiratory mechanics measurements in the same subjects. Caw was estimated at 3% of total compliance in healthy mice or 2.3 ± 1 μL/cmH2O (n=17). The technique detected changes in models of respiratory obstructive and restrictive diseases relative to control mice as well as differences in the two emphysema models studied. The changes in Caw were consistent with those seen in ΔCaw/ΔC, mWOB or Ers_20.5, with some variations according to the model, as well as with results reported in the literature in humans and mice. Direct Caw measurements in subjects as small as mice could prove useful to further characterize other respiratory disease models associated with airway remodeling or to assess treatment effects.

Central airway and peripheral lung structures in airway disease dominant COPD

The concept that the small airway is a primary pathological site for all COPD phenotypes has been challenged by recent findings that the disease starts from the central airways in COPD subgroups and that a smaller central airway tree increases COPD risk. This study aimed to examine whether the computed tomography (CT)-based airway disease-dominant (AD) subtype, defined using the central airway dimension, was less associated with small airway dysfunction (SAD) on CT, compared to the emphysema-dominant (ED) subtype.COPD patients were categorised into mild, AD, ED, and mixed groups based on wall area percent (WA%) of the segmental airways and low attenuation volume percent in the Kyoto-Himeji (n=189) and Hokkaido COPD cohorts (n=93). The volume percent of SAD regions (SAD%) was obtained by nonrigidly registering inspiratory and expiratory CT.The AD group had a lower SAD% than the ED group and similar SAD% to the mild group. The AD group had a smaller lumen size of airways proximal to the segmental airways and more frequent asthma history before age 40 years than the ED group. In multivariable analyses, while the AD and ED groups were similarly associated with greater airflow limitation, the ED, but not the AD group, was associated with greater SAD%, whereas the AD, but not the ED group, was associated with a smaller central airway size.The CT-based AD COPD subtype might be associated with a smaller central airway tree and asthma history, but not with peripheral lung pathologies including small airway disease, unlike the ED subtype.