Tracheobronchomalacia and large-airway obstruction

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

The central airway extends from the laryngeal inlet through the trachea and main bronchi. Fixed obstruction includes post-intubation or post-tracheostomy stenosis, tumour, inflammatory scarring and extrinsic compression. Variable extrathoracic lesions preferentially limit inspiration, while variable intrathoracic lesions affect expiration. Dynamic expiratory central-airway collapse is a separate problem in which airway calibre reduces excessively during breathing or cough because the cartilaginous wall, posterior membrane or both fail to maintain patency.

Symptoms are often disproportionate to ordinary asthma tests: an ineffective barking cough, difficulty clearing secretions, recurrent lobar infection, exertional or supine dyspnoea and transient choking may persist despite escalating inhalers. Acquired malacia can follow prolonged intubation, tracheostomy, relapsing polychondritis, compressive goitre, previous surgery or chronic airway disease. A focal obstructing lesion must remain in the differential, particularly when symptoms are progressive, the sound is monophonic, or haemoptysis and weight loss coexist.

Assessment is multidisciplinary because the diagnostic manoeuvre changes the observed collapse. Dynamic CT samples the whole airway non-invasively during a specified expiratory technique; flexible bronchoscopy visualises morphology, secretions and response to breathing manoeuvres and can biopsy or plan intervention. Treatment should address both mechanical narrowing and the factors amplifying symptoms, including obesity, reflux, dysfunctional breathing, infection and poor mucus clearance.

Key points

Large-airway obstruction may be fixed, variable or dynamic and can masquerade as asthma or COPD when the main sound is labelled simply as wheeze.
Tracheobronchomalacia describes weakness of cartilaginous airway support, whereas excessive dynamic airway collapse is exaggerated inward movement of the posterior membranous wall; both can produce symptomatic expiratory narrowing.
A barking cough, monophonic central wheeze, positional breathlessness, secretion retention, recurrent infection or symptoms triggered by forced expiration should prompt a central-airway assessment.
Inspiratory or biphasic stridor, focal haemoptysis, voice change, dysphagia, unilateral wheeze or progressive symptoms raise concern for tumour, stenosis, foreign body or extrinsic compression.
Routine inspiratory CT and resting spirometry can miss expiratory collapse; dynamic expiratory CT and functional flexible bronchoscopy answer different, complementary questions.
Percentage collapse alone must not define disease because substantial expiratory narrowing can occur in healthy people and varies with technique; symptoms, distribution and functional consequence are essential.
Flow-volume loop flattening can localise a fixed or variable obstruction, but a normal loop does not exclude tracheobronchomalacia or an intermittently obstructing lesion.
Management ranges from treating a cause and optimising secretion clearance to CPAP as a pneumatic splint, endoscopic therapy, carefully selected stenting or reconstructive surgery in an expert centre.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Acquired airway weakness

Prolonged intubation, tracheostomy, chronic inflammation and external compression can damage cartilage or posterior membrane support and cause dynamic collapse.

Congenital or connective-tissue disease

Developmental cartilage weakness and selected relapsing, connective-tissue or skeletal disorders predispose to malacia across different ages.

Fixed intraluminal obstruction

Tumour, foreign body, stenosis and inflammatory debris narrow the central airway independently of dynamic wall weakness.

Extrinsic compression

Thyroid enlargement, mediastinal mass, vascular anomaly or lymphadenopathy can compress trachea or main bronchi from outside.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Loss of airway support
Weak cartilage or excessive posterior membrane movement reduces central-airway calibre during expiration, coughing or high-flow breathing.
2
Flow limitation
Narrowing creates turbulent flow, wheeze or stridor and prevents expiratory flow from rising despite greater effort.
3
Secretion retention
Ineffective high-flow cough and dynamic closure trap mucus distal to the unstable or obstructed segment, and the downstream physiological effect determines clinical severity.
4
Recurrent inflammation
Retained secretions cause infection and cough, which further increases dynamic collapse and perpetuates airway irritation, with effects that increase as the pathological process progresses.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Threatened central airwayRed flag

Increasing stridor, suprasternal recession, inability to lie flat, drooling, exhaustion, agitation or declining air entry signals diminishing reserve. Escalate before complete obstruction makes transfer or conventional intubation impossible.

Dynamic collapse pattern

A harsh barking cough, expiratory monophonic noise, symptoms during forced exhalation, recurrent secretion retention and relief with positive airway pressure suggest expiratory central-airway collapse rather than small-airway bronchospasm.

Fixed stenosis pattern

Progressive exertional dyspnoea and biphasic noise after intubation, tracheostomy, airway surgery or neck radiotherapy should prompt tracheal stenosis assessment even if the event occurred months earlier.

Malignant obstructionRed flag

New focal or unilateral wheeze, haemoptysis, weight loss, hoarseness or recurrent pneumonia in the same lobe may reflect endoluminal tumour or extrinsic compression and needs urgent cancer-pathway imaging and bronchoscopy.

Foreign body possibility

Sudden cough or choking followed by localised wheeze or recurrent focal infection can indicate an inhaled object. Adults with swallowing impairment, dental procedures or intoxication may not recall aspiration.

Systemic cartilage disease

Auricular or nasal chondritis, inflammatory eye disease and airway symptoms raise concern for relapsing polychondritis, which can cause diffuse stenosis or malacia and requires urgent respiratory and rheumatology coordination.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Bedside airway assessmentFirst step
Why
Determine physiological danger and likely level before moving an unstable patient.
Interpretation and limitations
Stridor, voice change, work of breathing, posture, oxygenation and ability to speak matter more than loudness. Quietening noise with fatigue can indicate less airflow and impending failure rather than improvement.
02
Flow-volume loops
Why
Screen for reproducible fixed or variable upper and central-airway limitation.
Interpretation and limitations
Fixed obstruction can flatten both inspiratory and expiratory limbs; variable extrathoracic disease mainly flattens inspiration and intrathoracic disease expiration. Poor effort mimics flattening, and normal loops do not eliminate dynamic disease.
03
Contrast CT of neck and chest
Why
Map a fixed lesion, wall abnormality, extrinsic compression and distal lung consequences.
Interpretation and limitations
Report length, minimum calibre, distance from vocal cords and carina, adjacent vessels, nodes and post-obstructive change. A conventional breath-hold CT may appear reassuring despite symptomatic expiratory collapse.
04
Dynamic inspiratory and expiratory CT
Why
Quantify the distribution and morphology of central-airway change during breathing.
Interpretation and limitations
Interpret the acquisition manoeuvre, symptoms and airway shape together. A numerical percentage is not a stand-alone diagnosis; extensive collapse that reproduces disability carries more weight than an incidental threshold crossing.
05
Functional flexible bronchoscopy
Why
Directly observe airway behaviour, secretions and focal pathology while planning treatment.
Interpretation and limitations
An experienced bronchoscopist assesses quiet breathing, forced expiration and cough with carefully chosen sedation. Bronchoscopy can sample a lesion or infection, but sedation and positive pressure may alter dynamic collapse.
06
Cause-directed sampling
Why
Define malignancy, infection, inflammation or cartilage disease behind the narrowing.
Interpretation and limitations
Select cytology, biopsy, microbiology and blood tests through the MDT. Biopsy can bleed or destabilise a critically narrow lumen, so airway security and interventional capability take priority over tissue at the first procedure.
07
Physiological and functional assessment
Why
Establish the clinical consequence and competing contributors before invasive treatment.
Interpretation and limitations
Use spirometry, gas transfer, exertional testing, oximetry and validated symptom measures as appropriate. Review obesity, sleep-disordered breathing, reflux, vocal-cord dysfunction, asthma and cardiac disease that may amplify symptoms.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Asthma

Variable peripheral expiratory obstruction and treatment response favour asthma, while monophonic central noise and dynamic airway imaging support malacia.

Inducible laryngeal obstruction

Inspiratory throat symptoms with laryngeal closure during symptoms localise obstruction above the trachea, with targeted examination and testing used to resolve the uncertainty.

Fixed tracheal stenosis

A stable narrowed segment after intubation or surgery produces fixed flow-volume-loop flattening rather than predominantly expiratory dynamic collapse.

Endobronchial tumour or foreign body

Focal obstruction, haemoptysis or unilateral change requires bronchoscopy because dynamic symptoms do not exclude a structural lesion.

Excessive dynamic airway collapse

Predominant invagination of the posterior membrane may be described separately from cartilage weakness, though symptoms and specialist assessment overlap.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01SecureManage imminent obstructionFirst stepStridor, rapidly increasing work of breathing, hypoxaemia, exhaustion or imaging shows a critically narrow central airway.

1Keep the patient monitored in the position that best preserves breathing, call senior anaesthesia and airway specialists, and identify the level and likely mechanism from available information.
2Agree a primary and rescue airway plan before sedation or transfer, including rigid bronchoscopy, surgical airway or extracorporeal support availability where the anatomy makes conventional intubation unsafe.
3Relieve the obstruction through the appropriate expert technique, obtain tissue only when safe, and manage post-procedure oedema, bleeding, secretion load and recurrent narrowing in a critical-care-capable setting.

02DefineSeparate dynamic from fixed diseasePersistent barking cough, central wheeze, stridor, recurrent focal infection or poor response to otherwise appropriate asthma or COPD therapy.

1Reconstruct intubation, tracheostomy, malignancy, aspiration, inflammatory and positional history; examine the sound during inspiration, expiration, cough and recumbency without provoking an unsafe airway.
2Review flow-volume loops and obtain protocolled CT, adding dynamic expiratory acquisition when collapse is suspected and urgent contrast imaging when a mass or stenosis is possible.
3Discuss functional bronchoscopy with an expert service to confirm morphology, sample focal disease and relate observed obstruction to symptoms before committing to a stent or operation.

03TreatMatch intervention to mechanismObjective central-airway pathology is clinically consequential after relevant comorbid and secretion factors have been assessed.

1Optimise airway clearance, infection care, weight, reflux and coexisting respiratory disease; trial CPAP or non-invasive support when an expert believes pneumatic splinting may improve dynamic collapse.
2For benign fixed stenosis, consider balloon dilatation, radial incision or other endoscopic treatment under the interventional service; malignant disease may need debulking, radiotherapy, systemic therapy or a stent.
3Reserve stent trials and tracheobronchoplasty for carefully selected severe disease, explaining migration, mucus plugging, granulation, infection and the possibility that anatomical improvement may not relieve every symptom.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Acute airway failure

Severe central narrowing can cause exhaustion, hypercapnia and inability to ventilate, particularly during infection or sedation.

Recurrent infection

Secretion retention and poor cough clearance lead to repeated pneumonia and airway inflammation, particularly when baseline cardiopulmonary reserve is limited.

Bronchiectasis

Chronic retained infection distal to obstruction can permanently dilate and damage bronchi, and increasing the burden of otherwise local respiratory disease.

Procedure and stent harm

Airway interventions can cause migration, granulation, mucus plugging, bleeding or infection and require specialist surveillance, and potentially prolonging treatment and functional recovery.

Misdiagnosed refractory asthma

Failure to recognise central obstruction may lead to prolonged ineffective corticosteroid exposure and delayed airway treatment.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Document the characteristic symptom, positional or exertional trigger, exacerbation and infection burden, ability to clear sputum, exercise capacity and relevant quality-of-life limitation.
After CPAP or non-invasive ventilation is trialled, assess objective use, pressure tolerance, sleep effects, secretion handling and whether daytime function actually improves.
Following dilatation or endoscopic debulking, monitor for early bleeding, oedema and respiratory deterioration, then plan surveillance for restenosis according to cause and procedural findings.
A person with an airway stent needs expert follow-up for migration, mucus impaction, bacterial colonisation, granulation tissue and fracture; sudden symptom recurrence requires prompt reassessment.
For malignant narrowing, integrate airway patency with oncological response, performance status and goals of care so repeated procedures remain proportionate.
Revisit alternative contributors when technically successful treatment does not improve breathlessness, rather than assuming the airway measurement was the sole cause.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Noise can become quieter

A failing obstructed airway may generate less stridor as airflow falls, so declining sound accompanied by fatigue or poor air entry is ominous.

Loops localise imperfectly

Classic flattening patterns are useful examination concepts, but effort dependence and intermittent collapse mean normal spirometry cannot close a credible central-airway investigation.

Technique changes collapse

Forced expiration, cough, recumbency, sedation and positive pressure each alter airway calibre; a report should state the manoeuvre rather than presenting one percentage as immutable anatomy.

A stent is informative

In selected dynamic disease, a temporary stent trial may test whether stabilising the airway improves function, but the stent itself can cause cough, mucus retention and granulation.

Bronchodilator failure is a clue

Repeatedly escalating asthma treatment without variable airflow evidence should prompt reconsideration of a mechanical lesion, particularly when wheeze is monophonic or accompanied by voice change.

11Common pitfallsFrequent interpretation and management errors.

01
Calling every musical or harsh respiratory sound asthma without locating it in the breathing cycle.
02
Reassuring a symptomatic patient because a routine inspiratory CT or resting flow-volume loop is normal.
03
Diagnosing tracheobronchomalacia from a percentage-collapse threshold without linking morphology to symptoms and function.
04
Sedating or transferring a patient with critical obstruction before an experienced team agrees a rescue airway strategy.
05
Placing a central-airway stent without a cause-specific goal and arrangements for secretion care and surveillance.
06
Biopsying a nearly occlusive lesion before securing the capacity to control haemorrhage or complete obstruction.