What Causes Compression Atelectasis?
The term of atelectasis is associated with the collapse of a peripheral lung region, segmental or lobar, or to the massive collapse of one or both lungs, which motivates the impossibility to perform gas exchange.
This anomalous situation is a consequence of different pulmonary or extrapulmonary disorders, so this pathological entity is not a disease per se, but the manifestation of an underlying pulmonary pathology.
What Causes Compression Atelectasis?
In compression atelectasis, the pulmonary collapse occurs because the parenchyma is compressed by an extrinsic cause, resulting in alveolar air output through of the permeable airways.
In the collapse by contraction or healing, there is a decrease in pulmonary volume, due to the presence of local alterations or generalized fibrous tumors in the lung or pleura, preventing their complete expansion.
When the lung retracts, the intrapleural pressure becomes negative, leading to the deviation of mediastinal structures towards the affected side to compensate for volume loss, also causing hyperinflation compensatory of not affected pulmonary areas.
The symptoms that occur in an atelectasis depend fundamentally on two factors: the underlying disease and the magnitude of the obstruction. Sometimes atelectasis may not show symptoms, unless that the obstruction is important.
There is a great variability in relation to clinical manifestations and will also depend on the causal factors of atelectasis.
Whatever the cause of atelectasis, external compression, intrabronchial obstruction or inactivation or absence of surfactant, the collapse is accompanied by absorption of the air contained in the alveoli, associated with the loss of volume of the affected area.
Atelectasis compromises pulmonary functionalism whatever the pathology that produces it, causing alterations in the pulmonary mechanics and therefore in the gaseous exchange.
There is a commitment in the "pulmonary compliance" (compliance = volume/pressure), affecting this pulmonary elasticity in relation to the duration of pulmonary collapse, since the longer duration of atelectasis, higher insufflation pressures will be required to achieve an expansion of the collapsed territories.
The elastic resistances presented by lungs of the adult and the child are similar, however, the chest wall of the infant is more distensible, and the retraction of this wall contributes to creating a difficulty in insufflating the lungs in relation to the adult, so in these small the work necessary to introduce a volume of air in the lungs is superior with respect to the adult.
The pathophysiological mechanism of atelectasis formation is different depending on the cause of the collapse.
In the case of atelectasis due to bronchial obstruction, the air contained in the alveoli is reabsorbed, because the partial pressure of these is less than the pressure of the venous blood, resulting in the passage of the alveolar gases into the blood, until a complete collapse.
The symptomatology that we can find in the evolutionary course of compression atelectasis is as follows:
-A Cough: It occurs when the obstruction is increasing in frequency and intensity as a defensive mechanism, for trying to solve the obstacle.
-Hemoptysis: It may appear when the cause is the aspiration of a foreign body or infectious processes.
-Dyspnea, Cyanosis, And Stridor: Evident when the airway stenosis occurs.
-Chest Pain And Fever: due to super-infection secondary of atelectasis.
-Mediastinal Shift And Cardiac Noise: In case of massive atelectasis this shift to the affected side occurs, being this finding more frequent in small children, due to greater mobility of the mediastinum that they possess.
The diagnosis of compression atelectasis should begin with the performance of a complete clinical history, followed by a thorough examination of the patient, after which doctors will investigate the etiology of the process.
The diagnosis of compression atelectasis in children has many difficulties and a high level of clinical suspicion is needed to exclude atelectasis in children with acute or chronic symptoms of the respiratory tract.
Compression atelectasis is a sign of disease, but it does not suggest "per se" a specific diagnosis. It can be located in any lobe or lung segment, being the lower, both right and left lobes those collapsing most frequently.
The pulmonary collapse mainly occurs in compression atelectasis because the parenchyma is compressed by an external cause.
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