Overview

Imagine two siblings, Mona and Omar, decide to race to see who can drink their juice the fastest. Mona’s straw is made of sturdy metal. It doesn’t matter how much Mona sips or how fast; the straw remains open and strong, letting the juice flow easily. Omar’s straw, on the other hand, is made of soft plastic. The moment Omar starts sipping harder, the straw begins to bend and collapse. Instead of the juice flowing smoothly, Omar struggles to suck it up.

Mona represents a person with normal airways during exercise. Her airways are strong and stay open, even with deep breathing or intense physical activity, allowing air to flow freely. This lets her keep up with exercise effortlessly. Omar, on the other hand, is like someone with Tracheobronchomalacia (TBM) during exercise. Their airways are soft and floppy, much like that plastic straw. When he tries to breathe harder during exercise, his airways narrow or collapse, making it difficult for air to pass through. This leaves him short of breath, fatigued, and unable to tolerate physical activity. So while Mona runs ahead, cheerfully finishing her juice, Omar struggles, not because they’re less capable, but because their "straw" isn’t built for the task.

The purpose of this article is to focus on Tracheobronchomalacia (TBM) and how it results in exercise intolerance. It aims to explain why individuals with TBM experience difficulties during physical activities due to their airways collapsing under stress. 

The primary takeaways from this article are that tracheobronchomalacia (TBM) involves weakened walls of the trachea and bronchi, causing airway collapse and breathing difficulties, particularly during physical activity, often resulting in exercise intolerance. The condition can be either congenital or acquired. Common symptoms include shortness of breath, wheezing, and a chronic cough, which can have a huge impact on daily life. Diagnosis usually involves imaging and pulmonary tests, while treatment options include medications, surgeries, lifestyle changes, and pulmonary rehabilitation to enhance airway stability and breathing.

What is Tracheobronchomalacia (TBM)?

The term “Tracheobronchomalacia“ can be broken down into three words: trachea, bronchi, and malacia. Trachea and bronchi are airways, resembling an upside-down tree. The trachea forms the trunk and the bronchi form the branches. The trachea (windpipe) is a tube-like airway through which air enters the lungs from the larynx and branches into a bronchus in each lung.¹ The bronchi; the plural form of bronchus, are the main airways leading into the lung. Malacia means weakness or softening.² In simple terms, Tracheobronchomalacia means the weakness or softening of the trachea and bronchi.³

Tracheobronchomalacia is a condition where the walls of the trachea and bronchi are abnormally weak or softened. As a result, the airways can partially or completely collapse, making it difficult to move air into and out of the lungs.³

TBM is mainly divided into two classifications: primary and secondary. The primary form is called congenital disease (existing since birth), while the secondary type is called acquired disease (developed later in life).^3,4

TBM may occur due to various reasons, depending on whether it is present from birth or developed later in life. One cause of primary TBM is the cartilage. The trachea is made of cartilage which consists of rings supporting the trachea and bronchi together, that keep it open, so air can flow in and out as you breathe.¹ In children, the cartilage supporting the trachea and bronchi doesn’t develop properly during fetal development, making it soft and prone to collapse, leading to weak cartilage from birth.⁵ Other causes could be linked to genetic conditions such as Mounier-Kuhn Syndrome  Regarding gender, the reports are mixed. While some studies indicate no gender preference, others suggest a slight male predominance.⁶

Acquired TBM affects adults, especially older individuals. People who develop this condition later in life are more likely to have had long-term illnesses such as chronic respiratory conditions like emphysema (lung damage), asthma, and repeated lung infections may also contribute to the weakening of the walls of the trachea and bronchi.⁶

Some other causes could be posttraumatic. Posttraumatic causes are problems that happen after injuries or medical procedures, including complications such as prolonged intubation (prolonged use of a breathing tube), tracheostomy (a hole in the windpipe to help with breathing), chest trauma, or lung transplant. There is a slight male predominance in acquired TBM, though the reason is unclear.⁶

In many cases, congenital TBM in children gets better as they grow, but in adults, the condition often worsens over time and needs more complicated treatment. Children with congenital TBM often have sudden and short-term symptoms, with a higher chance of serious breathing problems during infancy. These symptoms may get better as the trachea develops. On the other hand, adults usually develop symptoms slowly, and these tend to get worse over time. Adults are also more likely to have daily life difficulties and feel tired more easily due to ongoing breathing problems.⁶

In general, TBM can lead to distressing symptoms that significantly impact quality of life. These symptoms often include wheezing, persistent shortness of breath, chronic cough, and phlegm production.⁶

According to one study, around one in every 2,100 kids is born with tracheobronchomalacia.¹

The exact incidence of TBM in adults is unclear because reports have been focused on specific populations rather than the population at large.⁴

Anatomy and Physiology of Breathing

The trachea, also known as the windpipe, is a tube that connects the throat to the lungs. It is supported by C-shaped cartilage rings that help maintain its structure and keep it open, allowing air to flow smoothly. At the base of the trachea, it splits into two bronchi, which act as branches leading to each lung. The bronchi further divide into smaller branches (bronchioles) that deliver air to tiny sacs called alveoli, where oxygen is exchanged for carbon dioxide. Together, the trachea and bronchi serve as the main pathways for air to travel to and from the lungs.¹

During exercise, the respiratory and cardiovascular systems work together seamlessly to meet the body’s increased oxygen demands. The lungs bring in oxygen from the air through the trachea and the bronchi and transfer it to the bloodstream through the alveoli. The heart then pumps this oxygen-rich blood to the muscles, supplying the energy they need for movement. As muscles use oxygen to produce energy, they generate carbon dioxide as a waste product. This carbon dioxide is carried back through the blood to the lungs, where it is exhaled. To keep up with the muscles' heightened oxygen demand, the heart beats faster, and breathing becomes deeper and quicker, requiring the trachea and bronchi to work harder to move more air into the lungs. This process ensures that oxygen delivery and carbon dioxide removal occur efficiently, supporting physical activity and maintaining energy levels. The intricate coordination of these systems enables the body to perform at its best during exercise.⁷

Exercise Intolerance 

The physiological process described above is typical of how physical activity works in healthy people. However, for those with TBM, the process is significantly more challenging. People with TBM have exercise intolerance, which means they are unable to handle heavy and long workouts as well as healthy people. This is because the trachea and bronchi in charge of entering oxygen into the lung are not completely open, making it difficult for individuals with TBM to receive the needed amount of air during exercise.¹⁰

TBM significantly limits a person's ability to exercise due to structural weakness in the walls of the trachea and bronchi. These weakened airways are prone to partial or complete collapse during breathing, particularly during exhalation when chest pressure increases. This collapse obstructs airflow, reducing the efficiency of ventilation and impairing oxygen and carbon dioxide exchange. During exercise, when the body demands faster and deeper breathing to meet increased oxygen needs, the problem becomes more difficult. The rapid airflow and increased intrathoracic pressure further worsen airway collapse, severely restricting airflow to the lungs.¹⁰

This restriction limits the delivery of oxygen to the bloodstream and, in turn, to the muscles, impairing their ability to produce energy efficiently. Individuals with TBM frequently experience shortness of breath even during light physical activity. This shortness of breath is accompanied by rapid fatigue and prolonged recovery times, making physical activity difficult and discouraging. Over time, the additional effort required for breathing places a significant energy burden on the muscles, further depleting the body's capacity for sustained physical movement.¹⁰ 

Certain activities or conditions can worsen symptoms. Actions that increase intrathoracic pressure such as coughing, crying, laughing, straining, or forceful exhalation can worsen airway collapse. Physical stressors such as swimming, diving, or lying flat can also worsen breathing difficulties.⁵

For those with TBM, this combination of reduced airflow, impaired oxygen delivery, and increased breathing effort creates a significant barrier to maintaining an active lifestyle, highlighting the need for specialised management strategies to support their quality of life.⁵

Diagnosis of TBM

Dynamic bronchoscopy is the gold standard for diagnosing TBM. A bronchoscopy is a minimally invasive procedure that allows healthcare providers to examine the airways and lungs using a bronchoscope, a thin tube with a light and camera. This procedure helps diagnose, evaluate, and sometimes treat conditions affecting the lungs, trachea, or throat.¹² Bronchoscopes can be flexible or rigid, with flexible bronchoscopes being more commonly used for tasks like keeping airways open and taking biopsies. Rigid bronchoscopes are used for more complex procedures, such as removing large objects, placing stents, or treating tumours or bleeding. Bronchoscopy is often recommended to investigate symptoms like chronic coughing, coughing up blood, or shortness of breath, to follow up on abnormal X-rays or CT scans, or to assess blockages, infections, or inflammation in the lungs. It may also involve taking mucus or tissue samples for lab analysis or placing stents to maintain open airways.¹³

Dynamic CT, also known as inspiratory and expiratory CT, is a specialised imaging technique used to assess airway conditions like TBM. This method captures images of the airways during both inhalation (inspiration) and exhalation (expiration) to evaluate their function under different breathing conditions. TBM is characterised by the weakening or softening of the trachea and bronchi, leading to airway collapse during exhalation. A dynamic CT scan helps find how much and where the airway collapses by comparing its size during inspiration and expiration. It helps quantify the degree of narrowing and provides real-time insights into the airway mechanics. Additionally, dynamic CT is valuable in differentiating TBM from other conditions, such as fixed airway obstruction or tumours. The ability to visualise and analyse the dynamic behaviour of the airways makes this technique essential for diagnosing TBM and planning appropriate treatment strategies.¹⁶

Pulmonary function testing (PFT) plays a critical role in evaluating and diagnosing TBM. These tests measure how well the lungs work by assessing lung volume, airflow, and gas exchange. In TBM, PFT can reveal problems associated with airway collapse, particularly during forced expiration.³

Management and Treatment

Management and treatment of TBM often involve a combination of medical, surgical, and lifestyle interventions. 

Treatment for tracheobronchomalacia depends on how it affects breathing. Options include medications to manage symptoms or infections, and supportive devices like CPAP (continuous positive airway pressure) machines, which provide continuous airflow to keep the airway open. In some cases, surgery may be necessary, such as using a bronchoscope to place a temporary stent in the airway, sewing mesh to the trachea for added support (tracheobronchoplasty), or attaching the trachea to spinal ligaments to prevent collapse (tracheopexy).³

Non-surgical management options also play a critical role in improving the quality of life for individuals with TBM. Pulmonary rehabilitation programs help enhance respiratory function and physical endurance, while lifestyle changes, such as avoiding environmental triggers and practising breathing techniques, can reduce symptoms. By combining these strategies, TBM can be effectively managed to minimise its impact on daily life.³

Summary

Tracheobronchomalacia (TBM) is a condition in which the trachea and bronchi become weak or soft, resulting in airway collapse and difficulty breathing. Individuals with TBM may experience exercise intolerance because their airways narrow or collapse under stress, making it difficult for them to acquire adequate air during physical activity. TBM may be congenital (existing at birth) or acquired later in life, with symptoms ranging from shortness of breath to chronic cough. It can be detected through dynamic bronchoscopy, CT scans, and pulmonary function testing. Medication, supporting devices, and, in severe situations, surgery are all viable treatment options. Pulmonary rehabilitation and lifestyle adjustments can also help manage the disease and enhance quality of life.