Pneumosclerosis

PNEUMOSCLEROSIS (from Greek pneuma—air and skleros—hard), hardening or compaction of the lungs, is the result of the development of connective tissue in the lungs and its transformation into scar tissue. The development of connective tissue in the lungs, being a definite stage of a productive inflammatory process arising in one or another part of the organ, represents a secondary process which ultimately manifests in the replacement of lung tissue, so rich in elastic fibers, by connective or scar tissue that is much less extensible and poorly elastic. Consequently, pneumosclerosis is a pathologo-anatomic and symptomatological concept, but not an etiological one. Pneumosclerosis does not represent a special "disease" in the usual old understanding of this term; it is a state of the organism in which its reaction to a primary irritation is manifested morphologically by an abundant proliferation of connective tissue that somehow disrupts the structure of the respiratory organs; subsequently, this process, progressing in its development, becomes woven into the cycle of both physiological and pathological phenomena developing in the respiratory organs, imparting a peculiar character to their course. Pneumosclerosis was first described by Laennec in 1819. Later—in 1838—Corrigan described pneumosclerosis complicated by bronchial dilation, giving it the name of cirrhosis of the lungs. In 1871, Brouardel described pneumosclerotic processes developing primarily in the pleura and successively involving the lungs as well (so-called pleurogenic scleroses). The main physiological function of the respiratory organs—gas exchange between the blood and the air environment—is carried out in the alveoli through the walls of blood vessels lining the alveoli in a dense network; in the process of filling the pulmonary alveoli with air, an essential role is played by the elastic properties of the lung tissue; the decrease in these elastic properties, which characterizes pneumosclerosis in particular, naturally lowers the functional capacity of the respiratory organs in the very first stages of the development of sclerosis; at the same time, the progressing sclerotic process disrupts the regularity and completeness of the blood supply to the lungs, and this disruption of pulmonary circulation in turn also leads to a decrease in function and contributes to the development of those morphological changes that characterize pneumosclerosis in a pathe-anatomical respect. The factors predisposing to the development of pneumosclerosis are age and living conditions. Pneumosclerosis is more often observed at an older age as a presenile phenomenon, but cases of its rapid development in childhood after acute infections—measles, whooping cough, bronchopneumonia—are not uncommon. Regarding living conditions, the factors predisposing to the development of pneumosclerosis are unhygienic working and living conditions that create the possibility of repeated infections, intoxications of the lungs, and especially their dustiness (see Pneumoconiosis). Pneumosclerosis should be considered not as a fixed, completed pathological change in the lungs, but as a process; its intensity and form of development are determined, firstly, by the nature of the primary agent that gave rise to the development of the process—dusting, infection, intoxication of the lungs, disorder of pulmonary circulation; secondly, by the inherited and acquired properties of the organism, the features of its physicochemical and biological reactions to a specific stimulus; and thirdly, by the living conditions in which the organism was and will be placed during the period of development of the process. Following the development of the process, one can find a great variety in both the anatomo-histological picture of the lungs affected by pneumosclerosis and the clinical manifestations of this process, which will differ both at different stages of the development of the process and, depending on the ratio of the local process to the general state of the organism, on the degree of perfection of coordination between the respiratory system and other organ systems.

In the genesis of the development of each pneumosclerotic process lies a primary moment: the damage and irritation of the lung tissue followed by a reaction to this irritation in the form of an inflammatory process; the nature of the further development of this process is determined by the aforementioned factors and their individual combination in each particular case. The more toxic the primary agent, the more violent the reaction it causes on the part of the organism; the features of physicochemical and morphological reactions, as well as the conditions of existence of the organism, determine either the rapid development of the process with a predominance of destructive phenomena and severe general intoxication, or the more sluggish course of the process with a predominance of proliferative phenomena; in cases where the harmful agent is a chronic infection or prolonged toxic exposure to small doses of an irritating substance (intoxication, dust inhalation) and where the reaction on the part of the organism is predominantly of a productive character, it is there that one particularly often has to encounter the development of a sclerosing process; this gave Letulle grounds to express the idea that "pneumosclerosis is the outcome of every chronic inflammation developing in any section of the tissues lying between the hilus and the pleura." Clinical observations establish that certain chronic infections and intoxications—syphilis, alcoholism, lead poisoning, and partly tuberculosis, the presence of arteriosclerosis and nephrosclerosis already existing in the organism—are the moments during which pneumosclerosis most frequently develops. Against the background of the aforementioned moments and pathological states of the organism, bronchopneumonia or pleurisy frequently lead to the development of pneumosclerosis. Considering every pulmonary disease from a modern clinical point of view not only as a local anatomical-pathological process developing in the respiratory organs, but as a process closely connected with the entire organism as a whole, pneumosclerosis in all the diversity of its manifestations must also be considered as a disease of the entire organism and 689 690 primarily as a disease connected with the state of the cardiovascular system, with which the respiratory system is so closely linked both anatomically and functionally; pneumosclerosis is above all a cardiopulmonary syndrome. As already mentioned, in the genesis of pneumosclerosis, along with primary inflammatory processes developing in the lungs under the influence of various stimuli, the disorder of pulmonary circulation also plays an equal role. Appearing in its origin as a secondary process, a reaction to one or another primary irritation, pneumosclerosis in its further development becomes already a factor causing in its turn both anatomical and functional symptoms that affect the general state of the organism and impose special features on the further course of that primary process which gave rise to its development; the consequence in turn becomes the cause of a subsequent cycle of phenomena. Without singling out the various types of pneumosclerosis into isolated, fixed clinical forms or nosological entities, but accepting them merely as orientational groups capable of combining and passing one into another, one can distinguish: 1. Dust pneumosclerosis; dust inhalation into the lungs causes dust diseases—pneumoconiosis (see), which in the majority of cases are accompanied by the subsequent development of pneumosclerosis. 2. Senile pneumosclerosis, characteristic of old people and developing parallel to general age-related sclerotic phenomena, and partly parallel to the physiological dust accumulation in the lungs. 3. Metainfectious pneumosclerosis, developing after prolonged and repeated bronchopneumonias and arising primarily in the lung tissue in the area of unresolved infectious foci. 4. Bronchogenic pneumosclerosis, the primary development of which begins in the bronchi and around the bronchi. A particular case of metainfectious pneumosclerosis is metatuberculous pneumosclerosis, appearing either in the form of apical pneumosclerosis or encompassing the entire lung and giving on the X-ray picture a pattern difficult to distinguish from pneumosclerosis of non-tuberculous origin: the same enlarged lymph nodes, the same fibrous strands along the course of the lymphatic and blood vessels and bronchi (peribronchitis), the same fibromatosously degenerated glands; this similarity of roentgenograms is so great that the differential diagnosis between metatuberculous and other pneumoscleroses—metainfectious and dust—by roentgenogram, without taking into account the entire clinical picture, is often impossible. This similarity is sometimes the source of erroneous conclusions about tuberculous involvement of the lungs where it does not exist. 5. Pleurogenic, or interstitial, pneumosclerosis arises primarily in the pleura during protracted, most often tuberculous forms of pleurisy; spreading along the paths of the connective-tissue partitions lying between the lobes and lobules of the lungs, the process then passes to the lung tissue, capturing entire lobes of the lung and deforming them. 6. Syphilitic pneumosclerosis manifests either in the form of massive sclerosis—white pneumonia of the fetus or newborns and interstitial pneumonia of adults—or more often in the form of a diffuse sclerotic process encompassing the bronchi, vessels, and in places the pulmonary parenchyma. Fibrous strands permeate the lung in all directions and reach the pleura; the picture is complicated by multiple bronchiectases; the sclerosing process also encompasses the mediastinal cellular tissue. 7. Pneumosclerosis of cardiac origin. Prolonged phenomena of stasis and disorders of pulmonary circulation, small hemorrhages, dilation of blood vessels, thickening of their walls, endarteritis, periphlebitis, extensive proliferation of connective tissue around the vessels and along the interlobar spaces, compression of the alveoli, the abundant presence in the connective tissue of blood pigment and its decomposition products, giving the sclerosed area, mainly in the lower lobes, a peculiar brownish-red color—all this creates the anatomical-pathological picture of pigmented sclerosis or brown induration of the lungs. Having developed depending on one or another etiological moment, pneumosclerosis subsequently causes changes in the surrounding tissues. The proliferation of connective tissue in the form of nodules or strands usually corresponds to the strands of interlobular tissue and the tissue accompanying the blood and lymphatic vessels; thickening in its further development, the connective tissue compresses individual groups of alveoli, reduces their lumen, causes their collapse and complete obliteration. Accordingly, other alveoli are stretched partly mechanically, partly vicariously, and thus pulmonary emphysema develops—an inevitable companion of pneumosclerosis—by virtue of the replacement of the elastic tissue of the lung by connective tissue. By the degree of development of pulmonary emphysema, one can judge the degree of development of sclerotic changes in the lungs. The bronchi undergo similar changes: some of them turn out to be compressed, others dilated; this second complication of pneumosclerosis—the development of bronchiectasis—already has its own complex clinical picture, extremely diverse depending on the degree of development of the process and almost always accompanied by subsequent infection. The pneumosclerotic process, capturing blood and lymphatic vessels, disrupts pulmonary circulation and creates in individual areas of the lung tissue and in the bronchi severe hyperemia and in particular varicose dilations of small veins, which can cause the onset of hemoptysis and pulmonary hemorrhages; in other areas, on the contrary, there is a decrease in blood supply and consequently a nutritional disorder. The mucous membrane of the bronchi and lung tissue, weakened in their nutrition, turn out to be unstable with respect to infections and sooner or later become infected. The further course will be determined by the type of infection, its virulence, and the state of the immuno-biological forces of the organism. In cases where pneumosclerosis has already caused the dilation of bronchi and the formation of bronchiectatic cavities, infection of these cavities is inevitable and manifests either in the form of a comparatively slowly proceeding disease or gives a violent picture of pulmonary suppuration with the formation of abscesses or foci of pulmonary gangrene.

> - . Pleurogenic pneumosclerosis presents a complex clinical and anatomical picture; most often the disease begins with tuberculous exudative pleurisy and, as a rule, develops slowly. Gradually developing adhesions—scars—draw the lung toward the pleura; the sclerotic process, spreading along the bronchi and blood vessels, encompasses the lung, compresses it, causes adhesions between the lungs and the spine, and as a result the lung, pleura, spine, pericardium, trachea—in a word, all organs of the thoracic cavity—turn out to be peculiarly fused together. The pleura itself thickens (up to one centimeter), acquires a dense, almost cartilaginous consistency, and in places deposition of calcareous salts is noted in it. The result of this sclerosing process is the displacement of the thoracic cavity organs, deformation of the chest, and curvature of the spine. The heart is displaced more often to the right, and this displacement is not accompanied by the rotation of the heart around its axis, which distinguishes this dextroposition of the heart from the congenital one. Electrocardiographic examination in dextroposition of the heart of sclerotic origin gives a normal electrocardiogram, whereas in congenital dextroposition the electrocardiogram is reversed. Displacement of the heart to the left is observed less frequently and is accompanied by inspiratory displacement of the mediastinum. Clinical manifestations of pneumosclerosis as a process of great importance in the development of pulmonary diseases can be reduced to three types corresponding to three stages of the development of the process. 1. The disease is revealed only by the formation of isolated scar cords developing after past infections and intoxications. Clinically, the disease in this stage manifests itself hardly at all and can be ascertained only radiologically or at autopsy. 2. The second stage is characterized by the development of emphysema and chronic bronchitis and clinically manifests itself with shortness of breath and cough with moderate expectoration of sputum in the mornings and clinical symptoms characteristic of emphysema and bronchitis. 3. The third stage is characterized by the development of bronchiectasis, pulmonary hemorrhages, displacement of organs, phenomena of heart failure, with an extremely diverse course depending on the predominant lesion of the bronchi, lung tissue, or pleura, on the degree of spread of the process, and on subsequent secondary infection; this infection is often tuberculosis. But the main, fundamental symptom of pneumosclerosis as such is shortness of breath, which initially appears only during physical exertion of the patient and later occurs more and more often and easily. Its pathogenesis lies in the reduction of the respiratory surface of the lung, its vital capacity (see Vital capacity of the lungs), oxygen starvation and, main of all, the difficulty and disorders of circulation in the lesser circulation; the organism compensates for these disorders with hypertrophy of the right ventricle, but as the reserve forces of the heart become exhausted, the symptoms of decompensation manifest themselves more and more brightly, and patients perish with phenomena of asystole. Secondary symptoms are cough and sputum discharge; in the initial stages of the development of pneumosclerosis they may be absent, while in the future their appearance, nature, and intensity are completely determined in each individual case by the predominance of one or another of the above-mentioned processes—emphysema, bronchitis, bronchiectasis, etc., the development of which is included in the cycle of pathological states developing in the presence of pneumosclerosis. Pain appears only when the process spreads to the pleura, and the temperature reaction is a consequence of the entry into the body of toxic substances of an infectious nature in secondary infections (infectious fevers) or a consequence of the entry into the body of tissue breakdown products and products of profound metabolic disturbance in morphologically altered tissues (resorption fever). Data from routine clinical examination of individuals suffering from pneumosclerosis by methods of percussion, auscultation, and fluoroscopy are as diverse as the individual forms of development of pneumosclerotic processes are diverse—these are symptoms of either emphysema, or acute or subsiding manifestations of secondary infection, or cavitary symptoms, or symptoms of complete obliteration of individual sections of the lungs, or symptoms of heart displacement and chest deformation, etc. Regarding preventive measures, the fundamental ones are social measures for the improvement of labor and living conditions, in particular concerns about sufficient stay in fresh air, physical work or exercises in hygienic conditions ensuring sufficient and perfect ventilation of the lungs. Since it has been established that individuals with massive dust load of the lungs, e.g., coal miners, in hygienic conditions, in rest homes or at health resorts, secrete coal dust with sputum for about a month, and therefore their lungs "cleanse" themselves of dust, it is necessary to insist on the necessity of long periodic leaves or changes of work for individuals working and living in dusty premises. In later stages of the development of pneumosclerosis, when work and major physical exercises are no longer accessible to the patient, systematic breathing exercises individually prescribed to each patient are appropriate. Enhancing lung ventilation and maintaining the working tone of the respiratory muscles, it significantly slows down the progressive development of the sclerotic process. Secondary symptoms and complications are subject to treatment according to individual indications, but since any pneumosclerosis overloads first of all the cardiovascular system and manifests itself as a cardio-pulmonary syndrome, it is possible to alleviate the patient's condition not by acting on the function of the respiratory organs, where the sclerotic process as an irreversible process remains almost outside the sphere of therapeutic impact, but on the function of the cardiovascular system, which can often be successfully regulated by prescribing cardiac remedies and establishing a work regimen appropriate to the patient's strength.