Tracheobronchomalacia

Definition

Tracheobronchomalacia is excessive narrowing of the trachea and main bronchi during expiration, caused by weakness of the airway wall. Two mechanisms are grouped under the term, and they are worth separating because they look different at bronchoscopy:

Severity is described by the percentage reduction in cross-sectional area on expiration, though the thresholds are contested — a substantial proportion of healthy people narrow considerably on a forced manoeuvre, which is why the finding must be interpreted against symptoms rather than in isolation.

Pathophysiology

Why breathing out is the problem

During quiet breathing, pressure inside the central airway keeps it open. During forced expiration, coughing or straining, pleural pressure rises above airway pressure and squeezes the airway from outside. A normal airway resists this because its cartilage is stiff; a malacic one does not, and collapses. The result is expiratory flow limitation in the large airways — a different mechanism from the small-airway limitation of COPD, although the two frequently coexist.

The cough paradox

Effective cough depends on high expiratory flow through an open airway. In tracheobronchomalacia, greater expiratory effort produces greater collapse, so beyond a certain point additional effort reduces flow at the point where it is needed. Patients discover this themselves — they describe coughing repeatedly and exhaustingly without clearing anything — and the observation is the foundation of the physiotherapy management.¹

Consequences

Retained secretions follow, then recurrent infection, and in some patients bronchiectasis. Exertional breathlessness reflects both flow limitation and the work of breathing against a collapsing airway. Severe cases can produce cough syncope, where the pressure generated during a coughing bout reduces cardiac output enough to cause a faint.

Co-morbidities

• COPD and emphysema — the commonest association in adults; the two mechanisms of airflow limitation compound each other.
• Obesity — raises intra-abdominal and intrathoracic pressure and is strongly associated with dynamic collapse.
• Obstructive sleep apnoea — frequently coexists; see obstructive sleep apnoea.
• Bronchiectasis and recurrent infection — both a consequence and a perpetuating cause.
• Gastro-oesophageal reflux — common, and a contributor to cough that is often the more treatable half of the symptom.
• Relapsing polychondritis and other cartilage disorders — uncommon but important causes of true malacia.
• Prior tracheostomy or prolonged intubation — localised malacia at the site of the tube or cuff; see tracheostomy.

Prevalence

Genuinely unknown, and almost certainly under-recognised. It is not looked for unless someone thinks of it, and the dynamic collapse that defines it is invisible on standard inspiratory CT. Reported frequencies in patients investigated for chronic cough or COPD vary enormously depending on the imaging protocol and the diagnostic threshold used. What is reasonably clear is that it is commoner in older adults, in obesity, and in advanced COPD, and that many patients carry a diagnosis of difficult asthma or refractory COPD for years before the airway collapse is identified.²

Causes

• Congenital — cartilage deficiency, often with other airway or vascular anomalies; usually presents in infancy and frequently improves with growth.
• Acquired, from pressure or injury — prolonged intubation, tracheostomy, chest trauma, previous airway surgery, radiotherapy.
• Chronic inflammation — long-standing COPD, chronic bronchitis, recurrent infection, cigarette smoke.
• External compression — a large thyroid goitre, vascular ring, tumour or mediastinal mass weakening the wall over time.
• Cartilage disease — relapsing polychondritis, Mounier-Kuhn syndrome, connective tissue disorders.
• Idiopathic — a sizeable group in which no cause is identified.

Symptoms

The characteristic picture

• A barking, brassy or seal-like cough — the single most suggestive feature.
• Breathlessness on exertion, often worse bending forward, lying flat, or after eating.
• Difficulty clearing sputum despite repeated, forceful coughing.
• Noisy breathing, wheeze or stridor that does not respond to bronchodilators.
• Recurrent chest infections and prolonged recovery from them.
• Cough syncope, or near-fainting during a coughing bout, in severe disease.
• Symptoms that are worse on exertion, when laughing, and when straining — all situations that raise intrathoracic pressure.

Warning signs

Diagnosis

Why it is missed

The diagnosis depends on imaging the airway while the patient breathes out. Standard CT is taken at full inspiration, when a malacic airway looks entirely normal. Spirometry may be normal or show non-specific obstruction, and bronchodilators do not help — so patients are commonly labelled as having difficult asthma or refractory COPD instead.

How it is diagnosed

• Dynamic expiratory CT — paired inspiratory and forced expiratory acquisitions, which is the non-invasive test of choice. It must be requested specifically; a routine chest CT will not answer the question.
• Bronchoscopy with the patient breathing spontaneously — the reference standard, allowing direct observation of collapse during quiet breathing, forced expiration and cough. Deep sedation or positive-pressure ventilation can abolish the finding.
• Lung function — may show a notched or oscillating expiratory flow–volume loop, but is frequently unremarkable and cannot exclude the diagnosis.
• Assessment for associated conditions — COPD, reflux, sleep apnoea, and cartilage disease where the pattern suggests it.

Interpreting the result

Collapse on imaging is not automatically the explanation for the symptoms. Healthy people narrow substantially on forced expiration, and the older diagnostic thresholds label a significant proportion of normal subjects as abnormal. The finding earns its place only when the degree of collapse fits the clinical picture and other causes have been addressed.³

Management

Treat what is treatable first

Most patients improve substantially without any airway-directed intervention. Optimising COPD or asthma treatment, treating reflux, weight loss where obesity contributes, treating sleep apnoea, smoking cessation, and vigorous treatment of infection between them account for much of the achievable benefit, and are the necessary first phase in every case.

Positive airway pressure

CPAP acts as a pneumatic splint, holding the central airway open during expiration. It is used at night in patients with coexisting sleep apnoea, and occasionally during the day or during airway clearance in more severe disease. For many patients this is the intervention that changes daily function most.

Airway clearance

Detailed below under the physiotherapist’s role, because it is where technique choice matters more than in almost any other airway condition.

Stents and surgery

Airway stenting is used mainly as a short-term trial to establish whether relieving the collapse actually improves symptoms, rather than as a long-term solution — complication rates with prolonged stenting are high. Tracheobronchoplasty, in which the posterior membrane is splinted surgically, produces good results in carefully selected patients at specialist centres, and a positive stent trial is usually required before it is considered.⁴

Living with tracheobronchomalacia

Unlearning the forceful cough

Most patients arrive having taught themselves to cough as hard as possible, because that is what works for everyone else. Learning that a gentler, more controlled technique clears more with less exhaustion takes practice and repeated reassurance — it feels wrong at first.

Positions and daily patterns

Many people find symptoms worse lying flat, bending forward, or after a large meal. Small adjustments — sleeping more upright, smaller meals, avoiding heavy lifting during a flare — are often more useful than they sound.

Infections

Chest infections are both more frequent and slower to clear. Having a plan — when to start increasing clearance, when to seek antibiotics, when to seek review — reduces both the length and the impact of each episode.

The diagnostic journey

Many patients have spent years being treated for asthma or COPD with medicines that did not help. Getting the diagnosis is often accompanied by frustration about the time it took; it is worth acknowledging rather than moving past.

Prognosis

Congenital malacia in infants generally improves as the cartilage stiffens with growth. In adults the condition is usually stable rather than progressive, and the trajectory is dominated by the associated conditions — COPD, obesity, recurrent infection — more than by the airway collapse itself. Well-selected patients who undergo tracheobronchoplasty report substantial and durable improvement in breathlessness and quality of life. The main avoidable harms are repeated ineffective treatment for a misdiagnosis, and progressive bronchiectasis from years of poor clearance.

Role of the physiotherapist

Assessment

Listen to the cough — the barking quality is diagnostic information available at no cost. Assess cough effectiveness at different efforts rather than at maximum only, sputum volume and the difficulty of clearing it, exertional tolerance and position dependence, and the patient’s current self-taught technique, which is usually what needs changing.

Clearance technique — the central intervention

The governing principle is to generate flow without generating collapse:

• Low-effort, prolonged huffs at mid to low lung volume rather than forceful coughing. Less effort clears more.
• Positive expiratory pressure — a PEP or oscillating PEP device splints the airway open during expiration and is often transformative. This is the technique to trial first.
• Pursed-lip breathing during exertion and during clearance, for the same reason.
• Active cycle of breathing with the forced expiration component deliberately gentle.
• Avoid forced coughing bouts, high-effort forced expiration technique, and manual techniques that encourage a hard cough — all of them increase collapse.
• Non-invasive ventilation or CPAP during clearance in more severe disease, where available, to maintain airway patency through the session.

See huffing and coughing and airway clearance techniques for the underlying technique, applied here at deliberately lower effort.

Exercise

Exertional breathlessness responds to training as it does elsewhere, and deconditioning is a major contributor. Use pursed-lip breathing during effort, expect symptoms to be worse in positions that compress the chest, and progress on symptoms. Where COPD coexists, standard pulmonary rehabilitation applies with the clearance modifications above.

Education

The single most valuable message is the cough paradox: harder is not better. Patients who understand why gentle technique works are far more likely to persist with something that initially feels inadequate.

Part 1 · References

1. Murgu SD, Colt HG. Tracheobronchomalacia and excessive dynamic airway collapse. Respirology 2006;11(4):388–406.
2. Buitrago DH, Wilson JL, Parikh M, Majid A, Gangadharan SP. Current concepts in severe adult tracheobronchomalacia: evaluation and treatment. J Thorac Dis 2017;9(1):E57–E66.
3. Boiselle PM, Michaud G, Roberts DH, et al. Dynamic expiratory tracheal collapse in COPD: correlation with clinical and physiologic parameters. Chest 2012;142(6):1539–1544.
4. Ernst A, Odell DD, Michaud G, et al. Central airway stabilization for tracheobronchomalacia improves quality of life in patients with COPD. Chest 2011;140(5):1162–1168.

References are numbered in citation order (Vancouver/BMJ style) and were current at the time of writing. Guidelines are living documents — verify against the latest version before clinical use.