Earliest Historical References to Tracheomalacia are from the 1930’s-1940’s, Describing Congenital Thoracic Vascular Abnormalities Which Resulted in Tracheal Obstruction
Demographics
Prevalence: acquired tracheobronchomalacia is more common than congenital tracheobronchomalacia
Tracheomalacia is Often Associated with Bronchomalacia in Pediactric Populations [MEDLINE]
Age/Sex: tracheobronchomalacia is more common in males >40 y/o
Male Predominance in Acquired Tracheobronchomalacia
Conditions Associated with Tracheobronchomalacia
Bronchopulmonary Dysplasia (BPD) (see Bronchopulmonary Dysplasia): occurs in up to 52% of infants with tracheomalacia
Cardiovascular Abnormalities: occur in 20-58% of patients with tracheomalacia
Physiology: likely related to embryonic foregut developmental abnormality
Idiopathic primary tracheomalacia has been considered the result of a defective foregut division that was not severe enough to cause tracheoesophageal fistula or esophageal atresia, but did result in an inherent weakness of the tracheal wall [MEDLINE]
Epidemiology: disease which is most commonly associated with tracheomalacia
Physiology: likely related to embryonic foregut developmental abnormality
Idiopathic primary tracheomalacia has been considered the result of a defective foregut division that was not severe enough to cause tracheoesophageal fistula or esophageal atresia, but did result in an inherent weakness of the tracheal wall [MEDLINE]
Congenital Syndromes Associated with Tracheobronchomalacia
Concurrent High-Dose Corticosteroid Therapy (see Corticosteroids)
Prolonged Intubation
Recurrent Intubation
Physiology: damage to tracheal cartilage at inflatable cuff site due to pressure necrosis, impaired blood flow, recurrent infection, mucosal friction, or mucosal inflammation
Clinical: usually segmental (maximum length is usually 3 cm)
Physiology: damage to tracheal cartilage at stoma/cuff/distal tube sites due to pressure necrosis, impaired blood flow, recurrent infection, mucosal friction, or mucosal inflammation
Clinical: usually segmental (maximum length is usually 3 cm)
Malacia: softness (generally of cartilage or bone)
Normal Tracheal Function
Trachea is Compliant, Allowing the Normal Intrathoracic Trachea to Dilates with Inspiration and Narrow with Expiration: this occurs due to the difference between intrathoracic and tracheal intraluminal pressures
Specific Maneuvers Where Intrathoracic Pressure is Significantly Greater Than Tracheal Intraluminal Pressure
Cough
Forced Expiration
Valsalva Maneuver
Tracheomalacia
Abnormal Diffuse or Segmental Weakening of Intrathoracic Tracheal Wall: due to intrathoracic pressure is exceeding the tracheal intraluminal pressure, resulting in exaggerated tracheal narrowing during expiration (and widening during inspiration
More Common Type
Mechanisms
Cartilaginous Malacia: associated with cartilaginous softening
Membranous Malacia with Excessive Forward Displacement of the Membranous Wall (Excessive Dynamic Airway Collapse): reduction and/or atrophy of the longitudinal elastic fibers of the pars membranacea
Abnormal Diffuse or Segmental Weakening of Extrathoracic Tracheal Wall: due to negative intrapleural pressure being transmitted to the extrathoracic trachea (due to pleural reflections), resulting in upper airway collapse during inspiration
Circumferential: anteroposterior and lateral tracheal narrowing
Clinical Classification Based on General Distribution
Segmental
Diffuse
Clinical Classification Based on Specific Anatomic Distribution
Tracheal
Bronchial
Tracheobronchial
Bronchomalacia
Weakening of Bronchial Wall: results in exaggerated bronchial narrowing during expiration and widening during inspiration
Isolated Bronchomalacia is Far Less Common Than Tracheobronchomalacia
Tracheobronchomalacia
Diffuse or Segmental Weakening of the Tracheal Wall Extending Into One or Both Mainstem Bronchi: results in exaggerated tracheobronchial narrowing during expiration and widening during inspiration
Diagnostic Gold Standard: to demonstrate dynamic tracheobronchial collapse
Technique: bronchoscopy is performed with minimal sedation (allowing patient to follow instructions)
Criteria for Tracheomalacia: >50% narrowing (although trials suggest that many normals may reach this diagnostic threshold)
Clinical Manifestations of Tracheobronchomalacia
General Comments
Asymptomatic: some cases
Misdiagnosis of Tracheobronchomalacia: tracheobronchomalacia may be misdiagnosed as asthma
Most Cases of Congenital Tracheomalacia Manifest During Early Childhood: usually manifest during first weeks-months of life
These are usually due to inherited diseases which weaken the tracheal wall (such as polychondritis)
Expected Course of Disease
Adult Patients: in most cases, tracheomalacia is progressive over time
Pediatric Cases (Healthy and Most Premature Infants): primary trachoemalacia is usually a self-limiting disease -> most infants outgrow the condition by 2 y/o
Pediatric Cases with Congenital Syndromes: tracheomalacia often persists and may be fatal in some cases
Precipitants of Clinical Symptoms
Active Infection
General Anesthesia
Progression of Airway Narrowing
Weaning from Mechanical Ventilation: removal of positive pressure (which had been splinting the airway open) may result in unmasking of the symptoms
Pulmonary Manifestations
Atelectasis (see Atelectasis): may occurs in cases with bronchomalacia
Pulmonary function and flow-volume loop patterns in patients with tracheobronchomalacia. Respir Care. 2013 Sep;58(9):1521-6. Epub 2013 Mar 12 [MEDLINE]
The first tissue-engineered airway transplantation: 5-year follow-up results. Lancet 2014;383:238-244 [MEDLINE]