DILATATION OF THE BRONCHIAL TUBES, CIRCUMSCRIBED AND DIFFUSED.
BY SAMUEL C. CHEW, M.D.
DEFINITION.—Enlargement of the calibre of a bronchial tube or tubes, whether confined to a limited portion of one tube, or reaching throughout a great part of its extent, or involving several or many tubes.
SYNONYM.—Bronchiectasis, from [Greek: bronchos], a bronchial tube, and [Greek: echtasis], an expansion.
HISTORY.—The change in the physical condition and size of a bronchial tube, designated as bronchial dilatation, never occurs as a primary affection, but is always the result of some preceding disease, especially of chronic bronchitis or fibroid phthisis. The full consideration of its pathological origin belongs, therefore, to the natural history of those causative affections.
Later writers have in general followed Laennec's description of the different varieties of bronchial dilatation; which, indeed, can hardly be improved upon, for such was the accuracy of that great clinician and pathologist as an observer that nothing was likely to escape him as regards physical conditions, though he may sometimes have been in error as to the theoretical explanation of what he saw. Previously to Laennec's observations dilatation of the bronchial tubes was, as he remarked himself, almost entirely overlooked both by pathologists and practitioners. The reason of this is evident from the considerations that a smaller tube when dilated would, except to the most careful examination, closely resemble a larger tube of normal size, and that a large dilatation might be mistaken by the ear at the bedside and by the eye at the necropsy for a pulmonary vomica.
Two principal forms of bronchial dilatation are met with. In the first, or diffused bronchial dilatation, known also as the cylindrical form, the tube is uniformly enlarged in calibre, so that, whereas in the normal state it would have admitted only a fine probe, in its enlarged condition it may be of the size of a goosequill. In this state it may be readily mistaken, when seen by itself, for a larger tube; but the alteration is conspicuous when the tube is seen to be larger than the branch from which it is given off. In the second or circumscribed form, which is also termed sacculated dilatation, a pouch-like or fusiform distension occurs in the continuity of a tube. In a third form, which is far less common, several successive enlargements are met with in the course of one tube, which thus presents a beaded appearance. It happens at times that all of these different varieties of dilatation may be encountered in the bronchial tubes of the same lung. The second, or sacculated, form is the most common, especially in young persons.
ETIOLOGY.—In both of the more common forms of bronchial dilatation the previous existence of bronchitis is to be regarded as the chief causative agency, though other conditions may serve to increase the dilatation when it has once been established. Laennec's observations led him to connect the occurrence of bronchitis with the production of dilatation of the bronchial tubes, though his explanation of the mechanism of this production was erroneous, inasmuch as he considered the accumulation of secretion in the affected tubes, and the forcible inspiratory efforts made in coughing to dislodge this accumulation, to be the direct causes of the enlargement. The part played by bronchitis in producing dilatation is, however, less immediate and mechanical than Laennec held it to be. It may, in a general way, be considered the direct cause of the cylindrical and the indirect cause of the saccular form of dilatation.
The long continuance of chronic bronchitis gives rise to weakness and atony of the bronchial walls, so that they yield to the pressure brought to bear upon them in the violent or protracted and repeated respiratory efforts that are made in coughing. In such cases the tubes which are themselves affected by the inflammatory process may yield throughout a greater or less extent of their continuity, and thus the cylindrical form of dilatation may be established. The same mechanism may be supposed to give rise to the beaded variety of the disease if the inflammatory action should be greater at several points along the course of a tube, with intervals of tissue in a healthier or less atonic state.
In the saccular form, on the other hand, the dilatation does not occur in the portion of the tube which is chiefly affected with the inflammatory process, but is the consequence of a local capillary bronchitis involving the ultimate ramifications of the affected tube and occasioning collapse of a portion of the lung. This collapse operates in two ways in causing a pouch-like dilatation of an adjacent bronchus—partly through the atmospheric pressure within the affected tube, tending to fill the space created by the collapsed portion, and partly by the traction of this collapsed lung-tissue outside of the tube.
In addition to the part played by bronchitis and atelectasis of the lung in occasioning bronchial dilatation, another important factor in its production is to be found in the condition described by Corrigan in 1838 as cirrhosis of the lung, and since recognized as interstitial pneumonia or fibroid phthisis. In this affection there is formed around the blood-vessels and terminal bronchi, as well as around the air-vesicles, a hyperplasia of the connective tissue, which, as is the case with connective-tissue formations in other situations, ultimately contracts, obliterating the air-cells, smaller bronchi, and blood-vessels, and thus converts the lung-tissue into a tough, fibrous mass. By the contraction thus produced the bronchial tubes of a larger size, which have been previously weakened by bronchitis and have lost their elasticity, are subjected to traction on all sides, and thus become dilated. Dilatations of all forms may thus be produced, cylindrical, sacculated, or beaded, according to the amount of lung involved in the contracting process and to the degree and situation of the bronchitis which favors the dilating action.
The determining causes, then, of bronchial dilatation are—1st, chronic bronchitis; 2d, atelectasis; and, 3d, fibroid phthisis or cirrhosis of the lung.
SYMPTOMATOLOGY.—The general symptoms of bronchial dilatation, as well as the course and duration of the affection, are such as belong to the pulmonary diseases favoring its production, especially chronic bronchitis and fibroid phthisis. The cough and dyspnoea of these diseases are aggravated by bronchial dilatation; but these symptoms, together with the impairment of nutrition, are due rather to the underlying affections than to the mere fact of dilatation. Increased and fetid expectoration, which often occurs in bronchial dilatation from retained and altered secretion, is by no means characteristic of this condition, since it may occur where no sign of dilatation exists.
There is generally some degree of dulness on percussion over a dilated bronchial tube, due to the condensation of the lung-tissue surrounding it, and varying in extent and degree with the amount of that condensation, and also with the amount of secretion retained within the tube. Sometimes, however, increased resonance of a tympanitic character is observed, especially if the dilatation be of the saccular form and near the surface of the lung. Such differences in the percussion sound are analogous to what occurs over a pulmonary vomica, which will generally give a dull sound, though, if the cavity be superficial and thin-walled, it may yield a tympanitic resonance. On auscultation bronchial respiration may be heard along the course of tubes affected with cylindrical dilatation when they are free from secretion; and this is more intense in proportion as the tube is more dilated and the lung-tissue around it more condensed. Bronchophony and increased vocal resonance also occur, and if mucus be present in the dilated tubes coarse moist râles will be heard. In a saccular dilatation there may be true amphoric breathing, with the gurgling sounds heard in a vomica. In some cases there is an alteration in the appearance of the chest-wall, which is retracted by the shrinking of the condensed lung beneath.
Now, of the auscultatory signs that have been mentioned, the bronchophony and increased vocal resonance, together with the percussion dulness, belong also to pneumonia, which, however, at least in its acute form, can be distinguished from bronchial dilatation by the previous history, the febrile movement, and the general phenomena of the case, and by the fact that the tubal breathing of pneumonia, besides being less persistent, is most frequently met with in the lower part of the lung, and that of bronchial dilatation in the upper part.
But the diagnosis between a dilated bronchus and pulmonary phthisis is in some cases a very difficult problem, the signs of the cylindrical form closely simulating those of the stage of deposit in phthisis, because involving the same physical condition, and those of the saccular variety corresponding often with the auscultatory signs of a cavity. In the former case there may be the same localized dulness on percussion, the same bronchial or broncho-vesicular breathing, and the same sinking or contraction of the chest-wall apparent on inspection. In the latter case there may be equally in saccular dilatation and in a vomica amphoric breathing, gurgling, and pectoriloquy. In the establishment of the diagnosis between these two conditions Austin Flint, Sr.,1 justly attaches importance to the circumstance that there is in general a greater degree of percussion dulness over a cavity than over a dilated bronchus, so that a relatively greater prominence of the auscultatory signs as compared with the degree of dulness makes the diagnosis of dilatation more probable. But the most important evidence on the point is to be gotten from the history of the case. If in a case where the auscultatory signs would leave the examiner in doubt there were found loss of flesh, fever, night-sweats, quickened pulse, and the other general phenomena belonging to phthisis, the existence of this affection would be rendered probable in the highest degree, and the auscultatory signs should be taken as corroborating an opinion founded on the general symptoms.
1 Dis. of Resp. Organs, p. 353.
Positive evidence, again, may be furnished by a microscopic examination of the sputa; the discovery of particles of lung-tissue or the so-called bacillus tuberculosis pointing clearly to phthisis. Conversely, the absence of the general symptoms of phthisis would, in a case presenting the above auscultatory signs, render it probable that they are due to bronchial dilatation. Long-continued cough and abundant expectoration are the chief symptoms common in both forms of disease. There are, however, some cases in which even with the most careful examination and weighing of evidence the physician will be left in doubt, inasmuch as in some cases of otherwise well-marked phthisis the usual constitutional symptoms are absent or imperfectly declared. In such exceptional cases the estimate of probabilities is to be based on the fact that while bronchial dilatation is comparatively rare, pulmonary phthisis is extremely common.
PATHOLOGY AND MORBID ANATOMY.—Enlargement of the bronchi may be met with throughout almost the entire extent of a lung; when limited to a part of the organ the change most frequently occurs, according to Laennec, Rokitansky, and other observers, in the superior lobe and toward the anterior border. The tubes of the third or fourth order in respect to size are most frequently affected, the primary bronchi being never involved except in association with tracheal dilatation.
In the different forms of dilatation the bronchial walls are found in various states. In the cylindrical variety they are for the most part thickened and hypertrophied, both as to the mucous and the fibrous coats; the mucous membrane being in a catarrhal state, covered often with muco-purulent discharge, and easily broken down and detached, while underneath the white fibrous coat is sensibly thickened.
In the sacculated form, on the other hand, the bronchial wall generally presents a thin and atrophied appearance, the mucous membrane undergoing but little change, except that the stretching to which it has been subjected gives it a smooth and shining look. This difference in the degree of thickening of the bronchial walls in the two forms of dilatation is in part due to the fact that in the saccular variety the enlargement in calibre is far greater than it is in the cylindrical form for a corresponding extent of a tube, so that its wall is much more stretched and attenuated, and thus the tendency to hypertrophy which has play in the cylindrical form is more than overcome in the saccular. But the chief reason of the difference in the state of the walls in the two forms of dilatation is found in the different modes in which they are respectively brought about, as already described.
DIAGNOSIS.—It has been shown that the determination of the existence of bronchial dilatation is at times one of the most difficult problems in diagnosis, from the fact that the auscultatory signs belonging to it may be equally met with in other affections, especially in pulmonary phthisis. The diagnosis is to be established, when this is possible, only by a careful consideration of the physical signs in connection with the general symptoms, so that the sources of doubt arising from the one set of phenomena may be as far as possible corrected by the other. These signs and symptoms, and the various affections to be discriminated by them, have been sufficiently set forth under the head of Symptomatology. While in this way a clear conclusion may be reached in many cases, yet there are others in which, notwithstanding the utmost care, there may still be a doubt as to whether the symptoms and signs indicate a dilated tube or a pulmonary cavity.
PROGNOSIS.—The prognosis of bronchial dilatation is directly connected with that of the affections which chiefly give rise to it—viz. chronic bronchitis and fibroid phthisis. When chronic bronchitis has lasted long enough to cause dilatation, it is seldom if ever cured, and, though improvement may take place from time to time in its symptoms, yet the dilated bronchi can hardly undergo diminution in their size. And in fibroid phthisis, while the progress of the disease is often very slow, yet it is on a downward grade, and the connective-tissue contraction giving rise to the dilatation increases with the advance of the malady.
TREATMENT.—The treatment of cases of bronchial dilatation resolves itself in great degree into that of the underlying and causal diseases on which it depends. As regards methods specially directed to the areas of dilatation, they consist of alterative, astringent, stimulant, and antiseptic remedies, either administered by the stomach or used by the process of inhalation. Cough may be allayed with the syrup of lettuce containing in each dose from 1/8th to ¼th of a grain of sulphate of codeia or 10 or 12 drops of the spirit of chloroform. If expectoration is very profuse, sulphate of atropia, in the dose of 1/100th to 1/80th of a grain, or the extract or tincture of belladonna, may be used. Turpentine and eucalyptol have a controlling influence over this symptom, and are specially beneficial if the bronchial secretion is fetid. They may be given by the mouth in the dose of minim v–xx in emulsion, and applied also by inhalation of their vapor or by spray. Inhalations of solutions of carbolic acid, minim j–x to an ounce of water, are more effective than anything else in checking fetor of the expectoration and the breath. This agent may also be administered by the mouth in the dose of fluidrachm j–iv of a 1 per cent. solution.