DEFINITION.—Inflammation of some part or of the whole of the mucous membrane lining the bronchial tubes between the bifurcation of the trachea and the alveoli or air-cells of the lungs. The inflammation may vary in grade from simple hyperæmia, with increased irritability, to the most intense engorgement, exudation, and tumefaction of the membrane, and in activity from the most acute and rapidly-progressive to the most chronic and protracted in duration.
SYNONYMS.—By the earlier writers the disease was called Peri-pneumonia notha, Angina bronchialis, and sometimes Erysipelas pulmonis. More recently it has been called Catarrhus suffocativus, Catarrhus pituitosus, Catarrhus bronchialis, Bronchial catarrh, and Bronchitis; Fr. Bronchite; Ger. Bronchialentzundung. Adopting the simple name of bronchitis, acute and chronic, in the further consideration of the subject I shall group the cases as they occur in general practice under the heads of Catarrhal, Mechanical, Capillary, and Pseudo-membranous Bronchitis.
HISTORY.—During all the earlier periods of medical history bronchitis was generally confounded with inflammation of the membrane lining the larynx and trachea on the one side, and with pneumonia and pulmonary phthisis on the other. Among the earliest writers who gave more accurate descriptions of bronchitis as a distinct disease were Badham, J. P. Frank, and Broussais, in the latter part of the eighteenth century. Full and accurate descriptions of the disease, differentiating it from inflammation of other parts of the respiratory organs, were not given, however, until the discovery of auscultation by Laennec, and its practical application aided by percussion to the physical examination of the chest. This important addition to the previous means for studying the exact location and extent of all diseases within the chest, and the largely increased attention given about the same time to the study of morbid anatomy, soon led to as accurate an appreciation of the existence and extent of disease in any part of the organs of respiration and circulation as in any of the structures of the human body.
ETIOLOGY.—The causes of bronchitis, like those of all other acute diseases, may be divided into two classes—namely, predisposing and exciting. The first embraces all those influences that are capable of rendering the mucous membrane of the air-passages more susceptible to impressions, whether by direct increase of the irritability of the structure or indirectly by altering the quality of the blood and the tone of the smaller blood-vessels. The second embraces such influences only as are capable of exciting a direct increase of irritability of the lining membrane of the bronchial tubes, with congestion of blood in its capillaries. Among the most common predisposing causes may be mentioned age, sex, occupation or modes of life, and climatic influences. As a general rule, the several grades of bronchitis are more prevalent during childhood and old age than during the active period of adult life. The British Registrar-General's Report for 1868 contained 33,258 deaths attributed to bronchitis, being 1344 for every million of inhabitants. Of the whole number, 10,550 died during the first three years of life, and 18,485 over forty-five years of age, leaving only 4223 to occur between the ages of three and forty-five years. This, however, is very far from indicating correctly the relative prevalence of the disease at the different periods of life, for the reason that the disease is far more fatal both in early life and in old age than in the early and middle periods of adult life.1 During the months of February, March, and April, 1882, in San Francisco, there were 65 deaths reported from bronchitis, of which 37 were of children under five years of age, 25 adults over forty years, and only 3 persons between five and forty years. During the same months there were reported 154 deaths from bronchitis in the city of Chicago, with about the same ratio in regard to age. In the city of Philadelphia, during the seven years from 1862 to 1869, the deaths from bronchitis at all periods of life aggregated 969, of which 495 were of children under five years of age, 14 over five and under fifteen years, and 460 of persons over fifteen years of age.2 These and similar mortuary statistics have led to the very general adoption of the opinion that early childhood and old age are pre-eminently susceptible to attacks of bronchitis. Yet my own clinical observations and records relating to the time and number of acute and subacute cases of bronchitis coming under my own care lead to a very different conclusion. By reference to those records I find a larger number of cases occurring between the ages of ten and thirty years than at any other period of life. Thus, during the first six months of the present year (1882) I recorded 59 cases of primary bronchitis; that is, cases not arising secondarily as complications of other diseases. Of this number, only 5 were children under ten years of age, 38 between ten and thirty years, and 16 over forty. It is probable that similar results will be obtained by all who will take the trouble to record the whole number of cases, instead of simply the number of deaths. The statistics of mortality in relation to this disease are deceptive, not only in regard to relative susceptibility of the human system to attacks at the different periods of life, but also in regard to the ratio of mortality of the disease itself. It is generally conceded that the chief mortality from this disease occurs during infancy or early childhood and in old age, cases rarely terminating fatally in youth or the more active period of adult life. Careful examination of cases will show that this fatality at the extremes of life is owing mainly to the greater tendency of the inflammation at those periods to extend directly from the bronchioles into the lobules of the lungs, thereby complicating the bronchitis with lobular pneumonia; and in more than half the cases reported under the head of bronchitis the fatal result was caused by the pneumonia instead of the bronchitis.
1 See Reynolds's System of Medicine, Amer. ed., vol. ii. p. 318.
2 See A Practical Treatise on the Diseases of Children, by J. F. Meigs, M.D., and William Pepper, M.D., 4th ed., p. 189.
Neither recorded facts nor my own clinical observations show any decided difference in the susceptibility of the sexes to attacks of bronchial inflammation.
Those occupations which confine the parties pursuing them much indoors, and at a temperature either too warm or too cold, strongly predispose to attacks of inflammation of the membrane lining the respiratory passages. Habitual exposure to a warm, confined air invites free exhalation from both the bronchial and cutaneous surfaces, with increased susceptibility, and consequently renders the individual more susceptible to all external impressions. Habitual passive exposure indoors to a low temperature represses the exhalations and causes the retention of some of the products of tissue-change which by their presence in the blood render the individual more liable to attacks of inflammation on the supervention of any exciting cause. For the same reasons the habitual wearing of too much warm clothing on the one hand, or too little on the other, predisposes to attacks of bronchial disease. Another error of importance is the unequal adjustment of clothing to different parts of the cutaneous surface. In children especially we often see an abundance of warm clothing over the whole body, while the legs and feet and neck have but a single covering, and sometimes none. And even adult women often go out loaded with warm clothing, while their feet and ankles are protected only by thin shoes and stockings. All those occupations that surround the workmen with an atmosphere filled with irritating gases, floating particles of stone, metal, or charcoal, or with the dust from grain and many vegetable substances, increase the liability of such workmen to attacks of all grades of bronchial inflammation.
It is universally conceded that bronchitis, as well as inflammation of all other parts of the mucous membrane lining the air-passages, prevails most in such countries as are characterized by a cold, damp, and variable climate. This can be well illustrated by comparing the prevalence of this class of diseases in that belt of our own country lying north of the fortieth parallel of latitude and east of the Rocky Mountains with the prevalence of the same class in the belt south of the thirty-third parallel and bordering upon the Atlantic and Gulf of Mexico. In the former the summers are comparatively short, with brief periods of high temperature, the winters cold, and the transition seasons, spring and autumn, long and exceedingly variable, with a predominance of cold and dampness. In the latter all the conditions just mentioned are substantially reversed. Perhaps the earliest reliable statistics we have bearing upon this subject are those collected by Samuel Forrey from the several military posts occupied by the United States Army, and given in a series of articles in the American Journal of Medical Science, and subsequently in an octavo volume, on the climate of the United States and its influence over the prevalence of diseases. The valuable facts presented by Forrey were added to by Daniel Drake, and given in full in his large work on the topography and diseases of the great interior valley of this continent. From these sources we learn that the average annual number of attacks of inflammation of the mucous membrane of the respiratory passages in every 1000 soldiers at Fort Snelling, in Minnesota, latitude 44° 53' N., was 600. At Fort King, fifty miles from the Gulf of Mexico, latitude 28° 58' N., the annual number of attacks average only 101.2 in every 1000 persons. Again, at Madison Barracks, near Sackett's Harbor, New York, the average number of attacks for every 1000 persons was 637.2, while at Key West, Florida, the average number of attacks was 208.9, and at Baton Rouge, Louisiana, only 207.2. Lest it should be thought that these five posts had been selected for the purpose of showing the most extreme contrasts, it may be added that Drake, after a laborious comparison of the statistics at all the military posts in the great interior valley from Fort Snelling at the north to Fort Jessup in Louisiana, the most southern, makes the "ratio of decrease in bronchial inflammations" as we pass from the north to the south as 31.5 for each degree of latitude.3 A similar comparison of the statistics of all the posts on the Atlantic Slope from Madison Barracks to Key West gives nearly the same results. The general inference here drawn concerning the much greater prevalence of bronchitis in the colder and more variable climate of the northern belt of our country than in the southern is fully corroborated by all the facts to be gathered from observations in civil life.