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 {166} 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 {167} than in the
southern is fully corroborated by all the facts to be gathered from
observations in civil life.
[Footnote 3: See _A Systematic Treatise on the Principal Diseases of
the Interior Valley of North America, etc., etc._, 2d Series, pp. 795,
796.]
A study of these same military statistics, representing the mean ratio
of the prevalence of diseases of the respiratory passages for a period
of ten years at nearly all the posts, will justify some other
inferences of interest besides the one just stated. According to this
general inference or rule, which is assented to by all the authors
within my reach, the three important factors in the climates most
favorable for producing bronchial inflammation are cold, variableness,
and dampness, the latter being emphasized by most writers as of
predominating influence. Yet the tables before us show that the highest
ratio of prevalence of inflammatory attacks of the mucous membrane of
the respiratory passages in the northern part of the interior valley
was at Fort Snelling, in the immediate vicinity of St. Paul, Minnesota,
being 600 attacks for every 1000 soldiers, while the lowest ratio was
at Fort Dearborn, on the site now occupied by the city of Chicago,
being only 102 for every 1000 soldiers. Looking at the posts in the
eastern part of the northern belt of country, Madison Barracks, at
Sackett's Harbor, at the eastern end of Lake Ontario, gives a ratio of
637 attacks for every 1000 soldiers, while Fort Niagara, at the mouth
of the Niagara River, near the western end of the same lake, gives a
ratio of only 355. Again turning to the posts in the southern belt of
country, the tables show at Fort Jessup, in the interior of Western
Louisiana, a ratio of 432.8, while at Fort Jackson the ratio was only
47.5 and at Fort King 101.2. As Fort Snelling is on the high rolling
prairie of the interior of Minnesota, noted for its cold and dry air,
and Fort Jessup on the elevated arid plateau between the head-waters of
the Sabine and the Red River, they cannot be noted for a high degree of
atmospheric moisture. On the other hand, Fort Dearborn was located on
the south-west shore of Lake Michigan, on the borders of a low and wet
prairie with a substratum of impervious clay, giving all the conditions
favorable for the prevalence of a high degree of atmospheric moisture.
And Forts Jackson and King are both on low alluvial lands only fifty
miles from the Gulf. Again, Fort Niagara is surrounded by all the
conditions favoring a high degree of atmospheric moisture, certainly
equal to those surrounding Madison Barracks in nearly the same
latitude, and yet the ratio of attacks in the latter was nearly double
those in the former. It is evident, therefore, that there exists some
important factor in the climatic relations of the inflammatory
affections of the respiratory passages besides temperature, humidity,
and changeableness. A glance at the topography of the whole country
will show that each of the posts giving a high ratio of
attacks--namely, Madison Barracks and Forts Snelling and Jessup, to
which may be added Forts Gratiot, Crawford, and Wood--are so located as
to be exposed to the prevalence of unusually severe winds or
atmospheric currents either from the north-east or the north-west and
west, with certain relations either to high mountain-ranges or
ocean-currents. For instance, from Madison Barracks the open valley of
the St. Lawrence River extends in a north-easterly direction to the
Atlantic Ocean, where the cold ocean-current is from the north,
favoring the pressure of cold atmospheric currents directly up the
valley from the north-east, reaching its termination at the eastern end
of Lake Ontario with but little diminution of force. The mountains of
Northern New York, Vermont, and New Hampshire seem to prevent the
deflection of these currents to the south, and help to keep them
directly in the line of the valley. That the high ratio of attacks of
bronchial and catarrhal affections at Madison Barracks is largely due
to the influences here described is corroborated by the fact that the
same class of diseases are much more prevalent in the province of
Quebec, through which the valley of the St. Lawrence extends, than in
the province of Ontario, as shown by the Registrar-General's Report in
reference to the several {168} military posts in the Canadas. Turning
to Forts Snelling and Crawford at the north and Jessup at the south, we
find them so situated in relation to the great mountain-chains to the
west as to be fully exposed to the cold and strong atmospheric currents
that sweep over the Plains from the north-west and west with such force
as to justify the popular title of blizzards. Without consuming more
time in details, it may be said that the force and direction of
atmospheric currents have quite as much to do with the development of
inflammations of the air-passages, including all grades of bronchitis,
as either temperature or humidity.
As might be inferred from what has already been said in relation to the
influence of climatic conditions, season of the year is also found to
exert a marked influence over the prevalence of bronchial affections.
Those parts of the year characterized by a low temperature, high winds,
and frequent thermometric changes are accompanied by the highest ratio
of prevalence of inflammations of the respiratory passages. Thus, the
statistics compiled from the records of all the military posts by Drake
show an average ratio for the four quarters of the calendar year of
119.8 for the first quarter, 72.7 for the second, 48.7 for the third,
and 99.6 for the fourth.[4] This corresponds closely with the results
of clinical records kept under my own observation through a series of
years.
[Footnote 4: See Drake on the _Principal Diseases of the Interior
Valley of North America_, p. 792.]
That tubercular deposits in the lungs, cancerous growths, emphysema,
and previous attacks of bronchitis, all strongly predispose the patient
to further attacks of the last-named disease, is proved by universal
clinical experience.
EXCITING CAUSES.--Exposure to sudden and extreme changes in atmospheric
temperature from warm to cold is almost universally regarded as the
chief exciting cause of inflammation of the bronchial as of all other
parts of the mucous membrane of the air-passages. More accurate and
detailed observations, however, show that such changes of temperature
are seldom productive of diseases of this class unless accompanied by
coincident high winds and humidity. My own studies concerning the
relations between special meteorological conditions and the prevalence
of particular diseases have led me to the following conclusions in
regard to bronchitis and inflammation of the mucous membrane of the
air-passages generally:
First. Many sporadic cases are caused, at any and all seasons of the
year, by exposure of limited portions of the cutaneous surface to cool
or cold currents of air while the rest of the body is well protected.
Females going out with thin shoes and stockings or sitting before open
windows with low-necked dresses, and children out on cold days with
naked legs from short trousers and defective stockings, afford many and
familiar examples of bronchitis from this cause.
Second. The sudden transition from a protracted period of intense dry
cold to a higher temperature with increased atmospheric humidity.
Almost every winter season, in the northern belt of the United States,
east of the Rocky Mountains, is characterized by several periods of
steady dry, cold air, varying from one to three weeks in duration,
during which the mercury in the thermometer often descends more than
20° C. (8-10° F.) below zero, and which generally ends in a sudden
change in the direction of the winds and a marked elevation of
temperature, constituting what is popularly called a thaw. Such changes
are very uniformly accompanied by a general prevalence of catarrhal
affections of the air-passages, including many cases of bronchitis.
This class of cases occur principally in the months of December,
January, and February.
Third. The occurrence of those cold north-east winds that during the
latter part of autumn and early part of spring so often sweep over the
whole extent of our Atlantic coast and press up the valley of the St.
Lawrence to {169} the great interior lakes, and the still more severe
currents that come during the same seasons from the north-west and
west, over all the wide plains that intervene between the great
mountain-chains to the west and the upper lakes and Mississippi River
to the east, are also accompanied by a high ratio of prevalence of
bronchial affections, as has been already shown from the records of the
several military posts. Most of these severe storms of wind are
accompanied by either snow or rain and a marked increase of ozone or
active oxidizers. In some of the severe snowstorms from the north-east,
occurring in the latter part of February and in March, I have found an
unusual amount of free ammonia. Whether either the ozone or the ammonia
has had anything to do with the production of the bronchitis cannot be
determined until the observations and records now being made under the
auspices of the American Medical Association have been continued for a
few years, by which adequate data will be furnished for reliable
deduction.
Besides ordinary meteorological conditions, bronchitis may be produced
by inhaling irritating substances, such as steam, irritating gases,
steel-dust, or minute particles of other metals or stone in workshops,
and the dust encountered in handling grain, etc. The disease has often
occurred in epidemic form without the presence of an obvious exciting
cause. It also frequently occurs in connection with certain general
fevers, more particularly with typhoid, measles, influenza, and
pertussis. It also sometimes, though more rarely, accompanies
rheumatism, constitutional syphilis, and erysipelas. The presence of
tuberculous and cancerous deposits in the lungs almost always provokes
more or less bronchial inflammation during some part of their progress.
Acute Bronchitis.
SYMPTOMATOLOGY.--The most common form of acute bronchitis, by many
writers styled catarrhal bronchitis, acute bronchial catarrh, etc.,
presents considerable variety of symptoms, according to the extent of
the membrane involved and the intensity of the inflammatory process. As
a general rule, the disease commences with slight chilliness or unusual
sensitiveness to slight changes of temperature, accompanied by a sense
of soreness and oppression behind the sternum and sometimes across the
whole chest, with a frequent and rather dry, harsh cough. In many cases
there is during the first day or two coincident congestion of the
membrane lining the nostrils, fauces, and larynx, causing sneezing,
with some feeling of soreness in the throat and hoarseness, also a
heavy dull pain in the head, much increased by coughing. By the second
day a moderate general fever has supervened, characterized by dryness
and moderate heat of the skin, flushed face, slight increased frequency
and fulness of the pulse, more sense of oppression and soreness in the
chest, with a continuance of harsh, dry cough, which often causes
soreness in the epigastrium, radiating laterally in the direction of
the attachments of the diaphragm to the inner surface of the ribs. On
the second or third day the inflamed membrane begins to be less dry and
the paroxysms of coughing bring up a scanty expectoration of a
tenacious, somewhat frothy mucus, which gradually increases until about
the fourth or fifth day, when it becomes more opaque, sometimes
yellowish, and much more easily expectorated. At the same time that the
expectoration changes to a more opaque condition, the general febrile
symptoms begin gradually to abate, and the cough is accompanied by less
sore pain both in the chest and head.
In the milder class of cases, the decline in all the general symptoms
is so rapid that by the seventh or ninth day, convalescence is
established. But in the more severe cases the more important symptoms
may continue through {170} two weeks, and convalescence not be complete
until the end of the third week. And in some of the cases the
inflammation does not disappear on the subsidence of the febrile
symptoms, but degenerates into a chronic form, causing a continuance of
cough, with some muco-purulent expectoration and slight soreness in the
chest, through an indefinite period of time. The disease is most likely
to take this course when it occurs in young persons having a scrofulous
diathesis, or in connection with eruptive fevers or pertussis, or in
the aged afflicted with rheumatism.
During the active stage of ordinary cases of bronchitis the urinary
secretion is diminished in quantity, redder than natural, and deficient
in chloride of sodium, and the bowels are inactive. But after the
crisis of the disease is passed, as indicated by the character of the
expectoration, the renal and intestinal discharges soon return to their
normal condition.
The results of auscultation and percussion in ordinary bronchitis,
limited to the membrane lining the larger bronchial tubes, are mostly
negative. In some instances during the first or dry stage, the
respiratory or vesicular murmur may be slightly harsher or more dry
than natural, and after the exudation or secretion of mucus, as
indicated by expectoration, there may be some coarse, moist râles,
which are removed temporarily by coughing, but return again in a little
time. These râles are heard much more in cases occurring either in
infancy or in old age than in youth or the middle period of adult life.
Percussion elicits only the natural degree of resonance throughout the
whole course of the disease, except in those rare cases in which
complete occlusion of the bronchial tube has taken place, causing
exclusion of air from certain lobules of the lungs, and consequently a
shade of dulness on percussion over such lobules.
Mechanical Bronchitis.
By mechanical bronchitis is meant those cases in which the inflammation
is caused by the direct action of mechanically irritating substances
floating in the inspired air, as fine particles of steel and other
metals, particles of stone, charcoal, and various vegetable powders and
fungi. Such substances, when inhaled, are liable to impinge on the
surface of the bronchial membrane and produce direct irritation and
inflammation, both acute and chronic.
Cases originating from this class of causes differ from ordinary acute
bronchitis chiefly in the mode of beginning and in the greater tendency
to continue in the chronic form. Instead of slight rigors, coryza, and
early development of moderate general fever, the patient generally
complains first, and for several days, of a sense of tickling or
fulness in the air-tubes, with occasional paroxysms of violent coughing
and little expectoration. Sometimes particles of the foreign substance
that is producing the inflammation may be seen mixed with the mucus or
matter expectorated. In many of these cases there is much soreness in
the chest and considerable dyspnoea, especially during the night,
followed by severe coughing in the morning, and a more free discharge
of mucus occasionally containing little streaks of blood, but which is
never intimately intermixed with the sputa as in pneumonia. If the
patient, by change of occupation or otherwise, ceases to be exposed to
the further action of the exciting cause, the symptoms soon begin to
abate, and a complete recovery may take place in from two to four
weeks. If exposure to the further action of the exciting cause is not
avoided, the disease will necessarily assume a chronic form, and in
many cases produce such changes as to materially shorten the life of
the patient.
{171} Capillary Bronchitis.
By this term is meant inflammation in the smaller bronchial tubes, but
not necessarily involving the true bronchioles as they terminate in the
air-cells. It may arise from all the causes that are capable of
exciting inflammation in the larger and medium-sized tubes. It may
occur at any period of life, but is most frequent in infancy and early
childhood, and next in persons past the middle period of life.
The chief differences in the clinical history of this and ordinary
catarrhal bronchitis arise from the greater obstruction to the ingress
and egress of air through the inflamed tubes. The same degree of
tumefaction of the membrane that occasions but little obstruction in
the larger tubes is capable of completely obstructing many of the
smaller ones, and thereby causing much dyspnoea and sense of
oppression, with frequency of respiration, accompanied at first by an
abundance of dry râles in all parts of the chest, followed later by the
complete intermixture of dry sounds and moist submucous râles, the
latter caused by more or less exudation or secretion of mucus from the
inflamed mucous membrane. The addition of the tenacious mucous
exudation to the previous tumefaction of the membrane, often so far
obstructs the ingress of air to the air-cells of the lungs that the
respirations become short, very frequent and noisy, with blueness of
the lips, coldness of the extremities, drowsiness, and soon death from
suffocation. This result, however, is seldom met with except in quite
young children and in persons enfeebled by age or by previous disease.
In cases which do not thus tend to an early fatal result from the
direct obstruction of the bronchi the respirations continue frequent,
in young children sometimes reaching 50 or 60 respirations per minute,
with much dyspnoea and restlessness; the pulse is quick, but not in
proportion to the respirations; the expression of countenance is
anxious and often slightly bloated, with a leaden hue of the prolabia;
the wings of the nose expand and the chest heaves with each
inspiration, giving a great variety of dry, whistling sounds generally
throughout the whole chest, which after the first two or three days
become mixed with sharply-defined submucous râles, and in the later
stages give place to the latter entirely. The cough is frequent and
inefficient, on account of the difficulty of getting sufficient air to
make it satisfactory. The temperature varies from 38° to 39.5° C.
(101-103° F.), seldom rising above the latter figure unless complicated
with lobular pneumonia. The urine is generally scanty and deficient in
the chlorine salts, and the bowels are inactive. The labored efforts of
breathing in many cases make the upper and anterior part of the chest
appear more prominent than natural, and even more resonant on
percussion on account of temporary emphysema from over-distension of
the air-cells in those parts, while in some parts of the lower and
posterior portions there is less expansion and less resonance than
natural from the occlusion of some of the bronchi and the partial
obstruction of others leading to those parts of the lungs.
Between the third and fifth days usually the mucous exudation, which up
to that time had been scanty and tenacious, becomes more abundant and
more opaque, and in two or three days more assumes a distinct
muco-purulent character and is much more easily expectorated. As that
which comes from the smaller bronchial tubes is less mixed with air,
and consequently less frothy than that which comes from the larger
tubes, the two qualities of matter may often be recognized in the same
mouthful of sputa; and if the whole be placed in water, that from the
smaller tubes will drop lower in the water, or sink to the bottom if
detached from the other, which floats freely upon the surface.