TABLE 2

Computed tomographic and magnetic resonance imaging studies

First author/yearStudy purpose and designPopulationDiagnostic modalityDiagnostic criteriaFindingsDiscussion
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 scanLAC ≥70% reduction in the CSAMean tracheal collapsibility improved by 34% in post-operative CTDynamic 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 CSASeven patients showed a tracheal collapse progression (>10% difference) between the scansTracheal 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 definedTM was 52% and 77% and BM was 55% and 63% during FVC for healthy and COPD patients, respectivelyMRI 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 scanLAC >50% and >80% reduction in the CSALAC prevalence was ∼15.1% when using >50% as a thresholdThe 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 MDCTLAC >50%, >75% and >80% reduction in the CSA were comparedECAC was observed in 35% of COPD, 39% of AECOPD and no healthy individuals when a >50% was used as a criterionECAC 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 scanECAC ≥50% reduction in CSAECAC 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 COPDCT scanTBM/EDAC ≥50% reduction of the airway lumenTBM/EDAC was found in 40% of COPD patientsFindings 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 scanTM ≥50% in the tracheal lumen CSA20% of COPD patients showed evidence of TMA 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 diseaseCT scan
Bronchoscopy at rest and during exercise (cycling; n=2).
EDAC ≥75% reduction of the airway lumenEDAC 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 COPDHelicoidal MDCTEDAC >50% reduction in CSAPrevalence of EDAC was 9.4%EDAC in COPD patients is independent of disease severity and may not relate to symptoms
ODonnell 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 COPD64-detector row CT scanTracheal collapse ≥80% reduction in CSAAverage 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 COPD4D MDCT scanTM criterion was not reportedEDAC (n=1), sabre-sheath trachea and TBM (n=1), as well as tracheal stenosis (n=1) were demonstratedLow-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 scanLAC criterion was not reportedExpiratory collapse was directly associated
with BMI (p=0.002)
Obesity is positively correlated with the degree of expiratory tracheal collapse
among COPD patients
ODonnell 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 scanTracheal collapse≥80% reduction in CSAThe 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 malesAge 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 COPD64-detector-row CT scanTracheal collapse ≥80% reduction in CSAPrevalence 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 scanTM criterion was not reported1st 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 scanExpiratory reduction in CSA of >50% and >80%, were both used73% of participants met the criterion (>50%) in one or both bronchiThe 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 bronchoscopyTM/TBM≥50% reduction in CSAAll 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 scanExpiratory reduction in CSA of >50%78% of healthy volunteers exceeded the current diagnostic criterion for TMThis 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 controlsDynamic cine MDCT with 64-detector rowTM >50% or >75% reduction in CSA during coughTM was found in 69% of patients with CF during forced expiration and in 29% during coughingTM 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 PEMDCT scanner with two-detector rowTBM ≥50% decrease in CSAFour (7.1%) patients were diagnosed as having TM or BMTBM 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 scanLAC ≥50%, and >70% in the CSAPrevalence of TM was found in 13.4% participants based on ≥50% criterionA 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 scanTBM was not definedTBM was not found at the end of expiration, but its prevalence was 13% during dynamic expirationDynamic 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 polychondritisMDCT helical scanLAC >50% reduction in CSACT findings were concordant with bronchoscopy in 97% of patientsCT 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 TM64-MDCT scanTM >50% reduction in CSA during coughing64-MDCT during a coughing protocol was technically successful in 94% of patients64-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 polychondritisHelical MDCTLAC >50% reduction in CSACT abnormalities were present in 94% and airway malacia in 72% of patientsDynamic 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 bronchiectasisVolumetric high-resolution 4- or 8-detector CTLAC ≥50% reduction in the CSAPrevalence of BM was found in 70% of patients at end-expirationAir 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 conditionsEight-detector row helical CT scanLAC ≥50% reduction in the CSACollapse 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 scanTBM ≥50% reduction in the CSATracheal collapse was found to be 58.9% pre- and 26.9% post-operatively during dynamic expirationDynamic 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 sarcoidosisHigh-Resolution CTLAC >50% reduction in CSABM was found in 61% of patientsBM 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-MRILAC >50% reduction in CSAA pathological collapse occurred in 33% of volunteers and in 69.6% of patients with COPDThe 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 lumenPrevalence of TM was found in 10% of the participants with suspected pulmonary embolismTM 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 TBMMulti-section helical MDCT scanLAC >50% reduction in the CSATBM was found in all 10 patientsPaired 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 scanDiagnostic criterion for TM was not reportedCollapsibility 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-expirationPatients 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, bronchoscopyLAC >50% reduction in the CSAAll 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 collapseCT scans (spiral and cine), cine-MRI, bronchoscopy≥50% collapse of the CSABronchoscopy correlated with cine CT. MRI demonstrated similar time curves of tracheal CSA to cine CTCine 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 systemDiagnostic criterion for TM was not reportedCollapse was 30±13% and 50±15% in forced expiration, and 38±16% and 75±12% during coughing in healthy and patients with TM, respectivelyCollapsibility 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 scannerTM >70% reduction in the CSATrachea 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

#The studies by Litmanovich et al. 2010 and Boiselle et al. 2009 were not analysed as part of the main results as the participants of both studies were included in O'Donnell et al. 2012. The study by Boiselle et al. 2013 was not analysed as part of the main results as the participants were included in O'Donnell et al. 2014. TBM: tracheobronchomalacia; GERD: gastro-oesophageal reflux disease; OSA: obstructive sleep apnoea; MDCT: multi-detector CT; LAC: large airway collapse; CSA: cross-sectional area; EDAC: excessive dynamic airway collapse; CT: computed tomography; TM: tracheomalacia; MRI: magnetic resonance imaging; BM: bronchomalacia; FVC: forced vital capacity; ILD: interstitial lung disease; ECAC: excessive central airway collapse; CF: cystic fibrosis; PE: pulmonary emphysema; CTPA: pulmonary angiography.