Excessive dynamic airway collapse in a small cohort of chronic obstructive pulmonary disease patients

Quantifiable features of a tidal breathing phenotype in dogs with severe bronchomalacia diagnosed by bronchoscopy

Dynamic lower airway obstruction is the primary component of canine bronchomalacia, but the ventilatory function remains underinvestigated. This prospective study analyzed tidal breathing characteristics in 28 dogs, comprising 14 with severe bronchomalacia diagnosed by bronchoscopy versus 14 without respiratory disease. Spirometry was conducted in all dogs. Bronchoscopy with bronchoalveolar lavage or brush under anesthesia was performed in 14 dogs with cough and expiratory effort. Severe bronchomalacia was defined by the severity of collapse and total number of bronchi affected. Ventilatory characteristics were compared between groups. Results revealed that dogs with severe bronchomalacia had lower minute volume (218 vs 338 mL/kg, p = .039) and greater expiratory-to-inspiratory time ratio (1.55 vs 1.35, p = .01) compared to control dogs. The tidal breathing pattern of dogs with bronchomalacia was different from that of normal dogs, and the pattern differed from the concave or flat expiratory curves typical of lower airway obstruction. Compared to control dogs, dogs with severe bronchomalacia had a significantly prolonged low-flow expiratory phase (p < .001) on the flow-time plot and a more exponential shape of the expiratory curve (p < .001) on the volume-time plot. Flow-time index ExpLF/Te (>0.14) and volume-time index Vt-AUCexp (≤31%) had a high ROC-AUC (1.00, 95% confidence interval 0.88 to 1.00) in predicting severe bronchomalacia. In conclusion, the tidal breathing pattern identified here indicates abnormal and complicated ventilatory mechanics in dogs with severe bronchomalacia. The role of this pulmonary functional phenotype should be investigated for disease progression and therapeutic monitoring in canine bronchomalacia.

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

Improving Quality of Dynamic Airway Computed Tomography Using an Expiratory Airflow Indicator Device

PURPOSE

Dynamic computed tomography (CT) of the airways is increasingly used to evaluate patients with suspected expiratory central airway collapse, but current protocols are susceptible to inadequate exhalation caused by variable patient compliance with breathing instructions during the expiratory phase. We developed and tested a low-cost single-use expiratory airflow indicator device that was designed to improve study quality by providing a visual indicator to both patient and operator when adequate expiratory flow was attained.

MATERIALS AND METHODS

A total of 56 patients undergoing dynamic airway CT were evaluated, 35 of whom were scanned before introduction of the indicator device (control group), with the rest comprising the intervention group. Lung volumes and tracheal cross-sectional areas on inspiratory/expiratory phases were computed using automated lung segmentation and quantitative software analysis. Inadequate exhalation was defined as absolute volume change of <500 mL during the expiratory phase.

RESULTS

Fewer patients in the intervention group demonstrated inadequate exhalation. The average change in volume was higher in the intervention group (P=0.004), whereas the average minimum tracheal cross-sectional area was lower (P=0.01).

CONCLUSIONS

The described expiratory airflow indicator device can be used to ensure adequate exhalation during the expiratory phase of dynamic airway CT. A higher frequency of adequate exhalation may improve reliability and sensitivity of dynamic airway CT for diagnosis of expiratory central airway collapse.

3D-measurement of tracheobronchial angles on inspiratory and expiratory chest CT in COPD: respiratory changes and correlation with airflow limitation

Purpose

To assess tracheobronchial angles and their changes on combined inspiratory and expiratory thoracic computed tomography (CT) scans and to determine correlations between tracheobronchial angles and several indices of chronic obstructive pulmonary disease (COPD).

Materials and methods

A total of 80 smokers underwent combined inspiratory and expiratory CT scans. Of these, 65 subjects also performed spirometry and 55 patients were diagnosed with COPD. On CT scans, 3-dimensinal tracheobronchial angles (trachea–right main bronchus [RMB], trachea–left main bronchus [LMB], and RMB–LMB) were automatically measured by software. Lung volumes at inspiration and expiration were also automatically calculated. Changes in tracheobronchial angles between inspiration and expiration were assessed by the Mann–Whitney test. Correlations of the angles with lung volume, airflow limitation, and CT-based emphysema index were evaluated by Spearman rank correlation.

Results

The trachea–LMB angle was significantly smaller and the RMB–LMB angle was significantly larger at expiration than inspiration (P<0.0001). The trachea–LMB and RMB–LMB angles were significantly correlated with lung volume, particularly at expiration. The RMB–LMB angle was significantly correlated with airflow limitation and CT emphysema index (P<0.001–0.05) at inspiration and expiration, suggesting that narrowed RMB–LMB angle indicates more severe airflow limitation and larger extent of emphysema.

Conclusion

Tracheobronchial angles change during respiration and are correlated with severity of COPD and emphysema.

Exertional Dyspnea and Excessive Dynamic Airway Collapse

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

Tracheobronchomalacia/excessive dynamic airway collapse in patients with chronic obstructive pulmonary disease with persistent expiratory wheeze: A pilot study

BACKGROUND

Tracheobronchomalacia (TBM) refers to a condition in which structural integrity of cartilaginous wall of trachea is lost. Excessive dynamic airway collapse (EDAC) is characterized by excessive invagination of posterior wall of trachea. In both these conditions, airway lumen gets compromised, especially during expiration, which can lead to symptoms such as breathlessness, cough, and wheezing. Both these conditions can be present in obstructive lung diseases; TBM due to chronic airway inflammation and EDAC due to dynamic compressive forces during expiration. The present study was planned with the hypothesis that TBM/EDAC could also produce expiratory wheeze in patients with obstructive airway disorders. Hence, prevalence and factors affecting presence of this entity in patients with obstructive airway diseases were the aims and objectives of this study.

MATERIALS AND METHODS

Twenty-five patients with obstructive airway disorders (chronic obstructive pulmonary disease [COPD] or bronchial asthma), who were stable on medical management, but having persistent expiratory wheezing, were included in the study. They were evaluated for TBM/EDAC by bronchoscopy and computed tomographic scan of chest. The presence of TBM/EDAC was correlated with variables including age, sex, body mass index (BMI), smoking index, level of dyspnea, and severity of disease.

RESULTS

Mean age of the patients was 62.7 ± 7.81 years. Out of 25 patients, 14 were males. TBM/EDAC was found in 40% of study subjects. Age, sex, BMI, severity of disease, frequency of exacerbations and radiological findings etc., were not found to have any association with presence of TBM/EDAC.

CONCLUSION

TBM/EDAC is common in patients with obstructive airway disorders and should be evaluated in these patients, especially with persistent expiratory wheezing as diagnosis of this entity could provide another treatment option in these patients with persistent symptoms despite medical management.

Excessive Dynamic Airway Collapse Detected Using Nondynamic CT

Excessive dynamic airway collapse (EDAC) has been diagnosed using dynamic CT during inspiration and expiration. We herein report an asthma patient with EDAC that was detected incidentally using nondynamic CT. The patient presented with wheezing, cough and mild fever. Treatment for the asthma did not improve her wheeze. CT revealed tracheal narrowing and bulging of the posterior bronchial wall. The patient was diagnosed with EDAC by bronchoscopy. Her wheeze improved with continuous positive airway pressure therapy. Clinicians should be aware of the airway shape when performing nondynamic CT in refractory asthma patients because recognizing the existence of EDAC may help when deciding on the treatment strategy.