Atelectasis

ATELECTASIS (from Greek ateles-incomplete, imperfect and ektasis-stretching), a term denoting such a condition of the lung or any part of it in which the alveoli do not contain air and appear collapsed. Such parts of the lung have a dark grayish-red or bluish-red color, leathery consistency, do not crepitate upon palpation, and sink in water; their surface, in comparison with the surface of adjacent air-containing areas, somewhat recedes.-The following types of A. are distinguished: 1. Congenital A. (A. in the proper sense). In this case, the lung or certain parts of it are found to have been non-breathing from the birth of the child and retain their embryonic character. It is observed in stillborn children or in weak, non-viable, superficially breathing children who died soon after birth, as well as if during childbirth the respiratory center is damaged or the respiratory passages become blocked with mucus, meconium, etc., as a result of which the child dies from asphyxia. The microscopic picture of this A. is characterized by a juicy, cellular and nuclear-rich, embryonic stroma of the lung with alveoli in the form of slit-like cavities resembling glandular ones and lined with cuboidal epithelium. 2. Acquired A. In this case, it is a matter of secondary collapse of alveoli in a lung that was previously breathing. Hence the other name - collapse (collapsus-collapse). Collapse can be complete and incomplete (when some amount of air still remains in the alveoli).-According to the origin of acquired A., the following are distinguished: a) A. from pressure, occurring when external pressure equals or exceeds the internal, inspiratory pressure of air on the walls of the alveoli. This is most often observed with the accumulation of fluid (exudates or transudates) in the pleural cavities (rarely in the pericardium), with the accumulation of a large amount of gas (pneumothorax), with the development of voluminous tumors or aneurysms in the chest cavity, with severe deformities of the chest (ricketic kyphoscoliosis) and with an excessively high position of the diaphragm (ascites, meteorism, tumors of the abdominal cavity, echinococcus, etc.). Characteristic of such A. are its localization and the pale color of the atelectatic area, since the blood vessels are compressed along with the alveoli, b) A. from obstruction. If any bronchial branch becomes impassable to air for some reason, the corresponding part of the alveolar parenchyma is excluded from the respiratory act, and the alveoli gradually collapse. This is most often encountered in childhood with bronchitis of various origins (measles, whooping cough, influenza, etc.). A sign of this type of A. is that it always occupies the volume of one or several pulmonary lobes (depending on the number and caliber of the affected bronchial branches), and that due to congestive hyperemia the entire area acquires a dark bluish-red color. Often, hyperemia is joined by edema here, and the atelectatic focus becomes similar to splenic tissue-the so-called splenization. When obstruction of the bronchial branches is associated with an infectious process in them, pneumonia may subsequently develop. Similar types of A. can occur in the lower parts (especially at the lower edge) of the lungs without obstruction of the air passages in weak patients with very superficial breathing, where the absence of air movement also leads to collapse of the alveoli. The further fate of any A. depends on the duration of its existence. If it is short, then, after eliminating the pressure on the lung or after restoring the patency of the bronchus, the walls of the alveoli can expand, and the respiratory function can be restored. Otherwise, in most alveoli, due to desquamation and death of the epithelium, a more firm adhesion occurs, and then the fusion of the walls with each other, which leads to a greater or lesser thickening of the interstitial basis of the atelectatic area and its transformation, thus, into a dense leathery scarred focus (induration due to collapse). In a few places, the remaining epithelium survives, takes on a cuboidal form; such alveoli in appearance very much resemble embryonic ones. As for the clinical symptoms, course, prognosis, and treatment of A., they all depend entirely on the underlying process by which A. is caused.