Acute and chronic stenosis of the larynx and trachea: causes and pathogenesis

Causes of acute and chronic stenosis of the larynx and trachea

Among the etiological factors are the infectious-allergic, iatrogenic, neurogenic, traumatic, idiopathic, compression (compression of the larynx tracheal structures from the outside). The causes of acute stenosis of the larynx can be:

• acute inflammatory processes of the larynx or exacerbation of chronic (edematous, infiltrative, phlegmonous or abscessed laryngitis, exacerbation of chronic edema-polyposic laryngitis);
• mechanical, thermal and chemical trauma of the larynx;
• congenital pathology of the larynx;
• foreign body of the larynx;
• acute infectious diseases (diphtheria, scarlet fever, measles, typhus, malaria, etc.):
• an allergic reaction with the development of laryngeal edema;
• other diseases (tuberculosis, syphilis, systemic diseases).

The causes of chronic stenosis of the larynx and trachea can be:

• prolonged artificial ventilation of the lungs and tracheostomy;
• operations on the thyroid gland with damage to the recurrent nerves and the development of bilateral paralysis of the larynx as a result of a violation of its innervation (peripheral and central origin);
• mechanical trauma of the larynx and thorax;
• purulent-inflammatory diseases, complicated by perichondritis of the larynx and trachea.

[1], [2], [3], [4], [5]

Pathogenesis of acute and chronic stenosis of the larynx and trachea

The pathogenesis of acute and chronic cicatricial stenosis of the upper respiratory tract depends on the etiological factor. Damage to the mucous membrane, especially in combination with trauma to the muscles and cartilage of the trachea, leads to infection of its wall and the development of a purulent-inflammatory process in it. At various stages of stenosis formation, the development of hypoxia (oxygen starvation) and hypercapnia (an excess of carbon dioxide in the blood) is considered to be the main factors determining pathological manifestations. Accumulation of CO2 causes excitation of the respiratory and vasomotor centers. Against the background of acute hypoxia, the symptoms of the central nervous system develop: fear, motor excitement, tremor, disturbance of cardiac and vegetative activity. These changes are reversible with timely treatment. If the cause of stenosis is difficult to eliminate, then at the end of an acute period, from which the patient was withdrawn by tracheostomy. The disease takes a long chronic course.

The pathogenesis of chronic stenosis of the larynx and trachea depends on the intensity of the damaging factor, the time of its impact and the distribution zone. Paralytic stenoses of the larynx are caused by a violation of the mobility of its elements. The causes of these conditions can be paralysis of the larynx of various etiologies, ankylosis of the spinal fractures, leading to a median or paramedic position of the vocal folds.

Post-indubation changes in the larynx and trachea arise as a result of trauma during the introduction of the tube and its pressure on the mucous membrane of the larynx and trachea during the artificial ventilation of the lungs, non-observance of intubation technique, tracheostomy. Among other factors affecting the development of complications, note the duration of intubation, the size, shape and material of the tube, its displacement in the lumen of the larynx. The following mechanism of development of the cicatrical process is described: the damaging factor causes the formation of a mucosal and cartilage defect of the larynx and trachea, a secondary infection that causes chronic inflammation spreading to the mucous membrane, perichondrium and cartilaginous skeleton of the upper respiratory tract. This leads to the formation of rough scar tissue and scar deformation of the larynx and trachea lumen. The process is stretched in time and ranges from a few weeks to 3-4 months. Inflammation of the cartilaginous tissue is an obligatory component in the development of chronic stenosis.

The pathogenesis of post-indubation cicatricial stenosis of the larynx and trachea is the ischemia of the mucous membrane of the larynx and trachea in the pressure zone of the intubation tube.

Causes of development of cicatrical-stenosing process can be:

• trauma of the mucous membrane of the larynx and trachea during intubation;
• pressure of the inflatable cuff on the mucous membrane of the respiratory tract;
• shape and size of the endotracheal tube:
• material from which it is made;
• composition of the microflora of the lower parts of the respiratory tract (including bacterial inflammation):
• tracheostomy with damage to the cricoid cartilage, tracheostomy in the Bjorku:
• atypical lower tracheostomy;
• bacterial inflammation of the tracheostomy zone;
• duration of intubation.
• the medial surface of the arytenoid cartilage, the transversophilic connection, the vocal processes:
• posterior part of the glottis and inter-capillary zone;
• the inner surface of the cricoid cartilage in the subbottom part;
• tracheostomy area:
• place fixation of the inflatable cuff in the cervical or thoracic region of the trachea:
• the level of the distal part of the intubation tube.

Violation of mucociliary clearance leads to a stasis of secretion and promotes infection, which leads to perichondritis, chondritis, and then to necrosis, which extends to the cricoid cartilage, percutaneous transection and cartilaginous structures of the upper part of the trachea. At the same time, in the dynamics of the wound process, three periods can be clearly traced:

• melting of necrotic tissues and purification of the defect through inflammation;
• proliferation of connective tissue elements with the formation of granulation tissue, replenishing the damage:
• fibrosis of granulation tissue with scar formation and epithelialization of the latter.

Great importance in the pathogenesis of stenosis has the general condition of the patient, concomitant diseases, craniocerebral trauma, diabetes, age of the patient.

Stenosis of the upper respiratory tract, both acute and chronic, leads to the development of respiratory failure according to the obstructive type of varying severity. At the same time, the normal gas composition of the blood is not maintained, or is provided by the inclusion of compensatory mechanisms, which leads to a decrease in the functional capacity of the body. With prolonged hypoxia, the body adapts to new conditions through organ restructuring (changes in the lungs, cerebral circulation and intracranial pressure, enlargement of the heart cavities, disturbance of the coagulating system of blood, etc.). These changes can be called a stenotic disease.

As a result of the scar process against a background of chronic inflammation, structural and functional lesions of the larynx and trachea of varying severity develop which lead to persistent disability of patients.