Bezuidenhout et al. 2019 [51] | Retrospective single-centre study To evaluate patients with TBM after undergoing tracheobronchoplasty | 18 patients (males (n=5), females (n=13); mean age: 65±12 years) with COPD (n=7), GERD (n=14), OSA (n=8), cardiac disease (n=4) | 8-, 16- and 64-MDCT scan | LAC ≥70% reduction in the CSA | Mean tracheal collapsibility improved by 34% in post-operative CT | Dynamic CT could play an important role in assessing response to tracheobronchoplasty |
Nygaard et al. 2019 [29] | Retrospective/prospective single-centre study To assess TM over time (2 CT scans) in patients with excessive tracheal collapse | 20 patients with respiratory diseases (males (n=6), females (n=14); mean age: 68 years) | high-resolution MDCT scan | TM ≥50% reduction in the CSA | Seven patients showed a tracheal collapse progression (>10% difference) between the scans | Tracheal collapse regressed in half of the patients over a time period of 2 years |
Ciet et al. 2017 [31] | Prospective single-centre study Comparison of MRI to MDCT in assessing TBM | 12 participants (males (n=5), females (n=7); 9 healthy adults and 3 patients with COPD; mean age: 64.5 years, age range: 45–77 years) | 1.5-T Signa MRI 64-MDCT scan | Criterion was not defined | TM was 52% and 77% and BM was 55% and 63% during FVC for healthy and COPD patients, respectively | MRI was found to be a technically feasible alternative to MDCT for assessing TBM |
Nygaard et al. 2017 [30] | Retrospective single-centre study To compare four different image analysis methods for the diagnosis of tracheal collapse using MDCT | 353 patients (males (n=150), females (n=191), mean age: 60 years, age range: 18–88 years) with respiratory diseases (e.g. COPD, ILD, bronchiectasis) | 64-MDCT scan | LAC >50% and >80% reduction in the CSA | LAC prevalence was ∼15.1% when using >50% as a threshold | The different image analysis methods identified LAC in different patients. Thus, the diagnosis of LAC should not solely rely on MDCT images |
Leong et al. 2017 [6] | Prospective single-centre study To explore the prevalence of ECAC in stable and acute exacerbations COPD (AECOPD) patients | 40 COPD patients (males (n=19), females (n=21); age: 70.1±8.2 years); 64 AECOPD (males (n=40), females (n=24); age: 70.2±11.6 years); 53 healthy volunteers (males (n=35), females (n=18); age: 56.6±16.9 years) | 320-slice dynamic MDCT | LAC >50%, >75% and >80% reduction in the CSA were compared | ECAC was observed in 35% of COPD, 39% of AECOPD and no healthy individuals when a >50% was used as a criterion | ECAC can be present in up to one third of patients with stable COPD, and the abnormality does not seem to be worsened during AECOPD |
Bhatt et al. 2016 [44] | Retrospective multicentre study Assessing the association of ECAC to lung disease in smokers | 8820 ex- or active smokers (43.7% had COPD and 16.6% had asthma (males (n=4667), females (n=4153); mean age: 59.7 ±6.9 years)) | CT scan | ECAC ≥50% reduction in CSA | ECAC prevalence was 5% in ex- or active smokers and 5.9% in participants with COPD (n=229/3856) | The presence of ECAC was associated with worse respiratory quality of life in current or former smokers |
Sindhwani et al. 2016 [34] | Prospective single-centre study To assess expiratory wheeze in patients with obstructive airway disorders | 25 patients (males (n=14), females (n=11), mean age: 62.7±7.81 years) with COPD | CT scan | TBM/EDAC ≥50% reduction of the airway lumen | TBM/EDAC was found in 40% of COPD patients | Findings indicate value of screening patients with obstructive airway disease for TBM/EDAC |
El Sorougi et al. 2016 [33] | Prospective single-centre study To determine the prevalence of TM in COPD patients | 30 patients with COPD (demographics were not reported) | 64-MDCT scan | TM ≥50% in the tracheal lumen CSA | 20% of COPD patients showed evidence of TM | A significant proportion of patients with COPD had features consistent with TM on dynamic CT scanning |
Weinstein et al. 2016 [52] | Prospective single-centre study To describe the imaging characteristics of people presenting exertional dyspnoea | 6 military personnel (males (n=5), females (n=1), mean age: 39.5 years, age range: 24 to 53 years) with no underlying lung disease | CT scan Bronchoscopy at rest and during exercise (cycling; n=2). | EDAC ≥75% reduction of the airway lumen | EDAC was detected on expiratory images during dynamic CT (n=2) | EDAC may explain “unexplained” exertional dyspnoea and wheeze in military recruits |
Represas-Represas et al. 2015 [43] | Prospective single-centre study To investigate the prevalence of EDAC in COPD | 53 patients (males (n=46), females (n=7), mean age: 65±9 years) with COPD | Helicoidal MDCT | EDAC >50% reduction in CSA | Prevalence of EDAC was 9.4% | EDAC in COPD patients is independent of disease severity and may not relate to symptoms |
O’Donnell et al. 2014 [25]¶ | Prospective single-centre study To determine the tracheal collapse in COPD patients | 67 patients (males (n=38), females (n=29); age: 65.1±6.5 years) with COPD | 64-detector row CT scan | Tracheal collapse ≥80% reduction in CSA | Average forced expiratory collapse (62±16%) was greater to end-expiratory collapse (17±18%) | COPD patients display a wide range of tracheal collapse at end-expiration |
Wielpütz et al. 2014 [53] | Prospective single-centre study To assess the feasibility of low-dose MDCT | 3 patients (3 males; mean age: 63.3 years) with COPD | 4D MDCT scan | TM criterion was not reported | EDAC (n=1), sabre-sheath trachea and TBM (n=1), as well as tracheal stenosis (n=1) were demonstrated | Low-dose MDCT may have equal diagnostic impact as bronchoscopy for tracheal instability |
Boiselle et al. 2013 [54] | Prospective single-centre study To assess the tracheal collapse in morbidly obese, non-morbidly obese and normal weight COPD patients | 100 patients (males (n=52), females (n=48), mean age: 65±7 years) with COPD | 64-detector CT scan | LAC criterion was not reported | Expiratory collapse was directly associated with BMI (p=0.002) | Obesity is positively correlated with the degree of expiratory tracheal collapse among COPD patients |
O’Donnell et al. 2012 [40]# | Prospective single-centre study To explore the association between forced expiratory tracheal collapse and age or sex | 81 healthy volunteers (males (n=41), females (n=40); age: 47±17 years) | 64-detector-row CT scan | Tracheal collapse≥80% reduction in CSA | The mean % collapse was similar for males (55±23%) and females (52±17%). The mean % collapse was correlated to age (r2 = 0.40, p< 0.001) in males | Age and sex should be considered when assessing forced expiratory airway collapse for suspected TM |
Boiselle et al. 2012 [24]¶ | Prospective single-centre study To determine the prevalence of tracheal collapse in COPD patients | 100 patients (males (n=52), females (n=48); age: 65±7 years) with COPD | 64-detector-row CT scan | Tracheal collapse ≥80% reduction in CSA | Prevalence of TM was found in 20 participants (20%) | TM is observed in a subset of patients with COPD, but the magnitude of collapse is independent of disease severity |
Boiselle et al. 2010 [32] | Prospective single-centre study To assess the reproducibility of MDCT in measuring TM in healthy volunteers over time | 14 healthy volunteers (males (n=6), females (n=8), mean age: 48.7 ±13.8 years) | 64-MDCT scan | TM criterion was not reported | 1st and 2nd year measures of tracheal collapse were strongly associated (r2=0.98, p<0.001) | MDCT measurements of forced expiratory tracheal collapse in healthy volunteers is highly reproducible over time |
Litmanovich et al. 2010 [26]# | Prospective single-centre study To assess the forced expiratory bronchial collapsibility in healthy volunteers | 51 healthy volunteers (males (n=25), females (n=26); age: 50±15 years) | 64-detector row MDCT scan | Expiratory reduction in CSA of >50% and >80%, were both used | 73% of participants met the criterion (>50%) in one or both bronchi | The current data suggest the need for more rigorous criteria for the diagnosis of BM |
Wagnetz et al. 2010 [28] | Prospective single-centre study To establish the use of a novel MDCT for the evaluation of TM | 6 patients (males (n=5), females (n=1); mean age: 53 years, age range: 37 to 70 years) with suspected TM (medical history was not reported) | 320-row MDCT scan and fibreoptic bronchoscopy | TM/TBM≥50% reduction in CSA | All patients demonstrated TM/TBM with varying degrees of airway collapse (50% to >90% of the CSA) | The 4D MDCT, isotropic, isovolumetric and isophasic, of the central airway is promising for the diagnosis of TM/TBM |
Boiselle et al. 2009 [14]# | Prospective single-centre study To assess the tracheal collapsibility in healthy volunteers | 51 healthy volunteers (males (n=25), females (n=26); age: 50±15 years) | 64-detector row MDCT scan | Expiratory reduction in CSA of >50% | 78% of healthy volunteers exceeded the current diagnostic criterion for TM | This study emphasises the need for a more rigorous diagnostic criterion to prevent overdiagnosis of TM |
McDermott et al. 2009 [39] | Prospective single-centre study To determine the prevalence and severity of TM in adults with CF | 40 patients (males (n=22), females (n=18); mean age: 28±8, age range: 18–54) with CF and 10 controls | Dynamic cine MDCT with 64-detector row | TM >50% or >75% reduction in CSA during cough | TM was found in 69% of patients with CF during forced expiration and in 29% during coughing | TM depicted at dynamic cine MDCT is a highly prevalent finding in patients with CF |
Inoue et al. 2009 [45] | Retrospective single-centre study To evaluate the frequency of TBM associated with PE | 56 patients (males (n=55), females (n=1); mean age: 68.9 years, age range: 49–87 years) with PE | MDCT scanner with two-detector row | TBM ≥50% decrease in CSA | Four (7.1%) patients were diagnosed as having TM or BM | TBM might be under- diagnosed in some patients with PE when using the standard criterion (e.g. ≥50%) |
Ochs et al. 2009 [46] | Retrospective multicentre study To investigate the prevalence of TM in an emphysema cohort | 431 patients (males (n=267, mean age: 64 years, range: 41 to 76), females (n=164, mean age: 62 years, range: 41 to 76)) | CT scan | LAC ≥50%, and >70% in the CSA | Prevalence of TM was found in 13.4% participants based on ≥50% criterion | A large degree of tracheal collapse can be found at end-expiration in patients with emphysema |
Ferretti et al. 2008 [27] | Prospective single-centre study To compare dynamic and end-expiratory imaging to assess LAC in patients with suspected TBM | 70 patients (males (n=43), females (n=27); mean age: 57 years, age range: 12–79 years) with respiratory conditions (e.g. COPD) | 16-detector row helical CT scan | TBM was not defined | TBM was not found at the end of expiration, but its prevalence was 13% during dynamic expiration | Dynamic expiratory CT demonstrates a greater degree of LAC than the end-expiratory acquisition in patients with suspected TBM |
Lee et al. 2007 [50] | Retrospective single-centre study To compare the dynamic expiratory CT against bronchoscopy for detecting airway malacia | 29 patients (males (n=12), females (n=17), mean age: 60 years, age range: 36 to 79 years) with COPD and relapsing polychondritis | MDCT helical scan | LAC >50% reduction in CSA | CT findings were concordant with bronchoscopy in 97% of patients | CT is a highly sensitive method for detecting airway malacia and could serve as an effective, noninvasive test for diagnosing LAC |
Boiselle et al. 2006 [20] | Prospective single-centre study To describe the technical aspects of using 64-MDCT during coughing | 17 patients (males (n=6), females (n=11), age range: 62.4 years) with suspected TM | 64-MDCT scan | TM >50% reduction in CSA during coughing | 64-MDCT during a coughing protocol was technically successful in 94% of patients | 64-MDCT is technically feasible and has the potential to make significant contributions to the noninvasive diagnosis of TM |
Lee et al. 2006 [55] | Retrospective single-centre study To assess the prevalence of expiratory CT abnormalities, including malacia | 18 patients (males (n=3), females (n=15), mean age: 47 years; age range: 20–71 years) with relapsing polychondritis | Helical MDCT | LAC >50% reduction in CSA | CT abnormalities were present in 94% and airway malacia in 72% of patients | Dynamic expiratory CT should be considered a standard component of airway evaluation in patients with relapsing polychondritis |
Nishino et al. 2006 [36] | Prospective single-centre study To evaluate the frequency and severity of BM | 46 patients (males (n=10), females (n=36), mean age: 64 years, age range: 44–84 years) with bronchiectasis | Volumetric high-resolution 4- or 8-detector CT | LAC ≥50% reduction in the CSA | Prevalence of BM was found in 70% of patients at end-expiration | Air trapping in bronchiectasis might be greater in bronchiectasis patients with BM compared to those without |
Baroni et al. 2005 [38] | Retrospective single-centre study To compare the dynamic- and end-expiratory CT in assessing LAC | 14 patients (males (n=11), females (n=3), mean age 53 years old and age range: 19–79 years) with various conditions | Eight-detector row helical CT scan | LAC ≥50% reduction in the CSA | Collapse was greater in dynamic expiration than in end-expiration (p<0.004) | The reliance on end-expiratory imaging alone might result in a high level of false-negative results |
Baroni et al. 2005 [37] | Prospective single-centre study To describe the role of pre- and post-operative dynamic CT in patients undergoing tracheoplasty | 5 patients (males (n=4), woman (n=1); mean age: 62, age range: 56–78) | 8-MDCT helical scan | TBM ≥50% reduction in the CSA | Tracheal collapse was found to be 58.9% pre- and 26.9% post-operatively during dynamic expiration | Dynamic expiratory CT is a potentially valuable tool in the pre- and post-operative evaluations of patients undergoing tracheoplasty |
Nishino et al. 2005 [35] | Prospective single-centre study To investigate the frequency of BM associated with sarcoidosis | 18 patients (males (n=6), females (n=12); mean age: 47 years, age range: 29–64 years) with pulmonary sarcoidosis | High-Resolution CT | LAC >50% reduction in CSA | BM was found in 61% of patients | BM is frequently associated with sarcoidosis |
Heussel et al. 2004 [42] | Prospective single-centre study To assess the respiratory lumen diameter, change in the tracheal level during continuous respiration | 38 subjects, 23 patients with COPD (age: 59 years, age range: 41–68 years) and 15 healthy adults (age: 62 years, age range: 48 to 74 years) | Cine-MRI | LAC >50% reduction in CSA | A pathological collapse occurred in 33% of volunteers and in 69.6% of patients with COPD | The airway collapse is significantly larger in patients with COPD compared to volunteers |
Hasegawa et al. 2003 [21] | Retrospective single-centre study To determine the frequency of TM incidentally detected on CT pulmonary angiography (CTPA) | 163 (73 males (n=73), females (n=90); mean age: 60 years) with suspected pulmonary embolism | Single detector CT and MDCT (with 4 and 8 detectors) | TM ≥50% decrease in tracheal lumen | Prevalence of TM was found in 10% of the participants with suspected pulmonary embolism | TM is a relatively common finding in CTPA when assessing patients with suspected pulmonary embolism |
Zhang et al. 2003 [3] | Prospective single-centre study To compare standard- and low-dose CT images assessing tracheal lumen | 10 patients (males (n=5), females (n=5), mean age: 56 ±11 years) with bronchoscopically proved TBM | Multi-section helical MDCT scan | LAC >50% reduction in the CSA | TBM was found in all 10 patients | Paired inspiratory and dynamic expiratory CT images is a promising method for diagnosing TBM |
Aquino et al. 2001 [56] | Retrospective and prospective single-centre study To explore the measurements of the trachea between inspiration and end-expiration on CT | 10 TM patients (males (n=6), females (n=4); mean age: 60 years, age range: 42 to 84 years) and 23 normal control patients (males (n=15), females (n=8); mean age: 40 years, age range: 27 to 57 years) | CT scan | Diagnostic criterion for TM was not reported | Collapsibility in tracheal CSA was significantly greater in patients with TM (1.9±0.9 cm2) compared to controls (2.4±0.6 cm2) during end-expiration | Patients with TM demonstrate a higher airway collapse compared to controls |
Gilkeson et al. 2001 [4] | Prospective single-centre study To examine the role of dynamic inspiratory-expiratory imaging with MDCT in patients with suspected TBM | 13 patients (males (n=7), females (n=6); mean age: 49 years and age range: 14–88 years) with respiratory conditions (e.g. asthma, chronic cough, smoking) | MDCT scan, bronchoscopy | LAC >50% reduction in the CSA | All patients showed evidence of TBM of different degrees, 50–75% (n=3) 75–100% (n=7), and 100% (n=3) | MDCT with inspiratory-expiratory imaging is a promising method in the evaluation of patients with suspected TBM |
Heussel et al. 2001 [22] | Prospective (including retrospective analysis) single-centre study To compare CT, MRI bronchoscopy, in the diagnosis of LAC | 29 patients (males (n=10), females (n=19); mean age: 61 years, age range: 27–82 years) with suspicion of or previously bronchoscopically verified tracheal collapse | CT scans (spiral and cine), cine-MRI, bronchoscopy | ≥50% collapse of the CSA | Bronchoscopy correlated with cine CT. MRI demonstrated similar time curves of tracheal CSA to cine CT | Cine CT is able to obtain significantly improved evaluation of respiratory collapse. Cine-MRI promises functional information due to free choice of imaging plane |
Suto & Tanabe, 1998 [41] | Prospective single-centre study To evaluate tracheal collapsibility during coughing in patients with TM who underwent MRI | 6 patients (males (n=4), females (n=2); mean age: 40 years, age range: 44 to 68 years) with suspected TBM and 13 healthy volunteers (males (n=10), females (n=3); mean age: 40 years, age range: 17 to 63 years) | 1.5-T superconducting MRI system | Diagnostic criterion for TM was not reported | Collapse was 30±13% and 50±15% in forced expiration, and 38±16% and 75±12% during coughing in healthy and patients with TM, respectively | Collapsibility during forced expiration-inspiration and collapsibility during coughing was not significant in patients with TM during MRI |
Stern et al. 1993 [57] | Prospective single-centre study To define the range of intrathoracic tracheal diameters and CSA during forced respiration | 10 healthy volunteers (males (n=10), age range: 24–31 years) | CT using the model C-100 scanner | TM >70% reduction in the CSA | Trachea significantly decreased (p<0.001) from end-inspiration (280 mm2) to end-expiration (178 mm2) | Intrathoracic tracheal shape, sagittal and coronal diameters, and CSA can vary greatly during a forced respiration |