Atelectasis in bronchitis, congenital, etc. Airless condition in the
absence of exudation. Causes, congenital persistence in butcher
animals. Blocking of air tubes by exudate—ball valve. Desquamation of
ciliated epithelium. Compression by hydrothorax, pneumothorax, and
false membrane. Symptoms. Percussion flatness, juvenile respiration
elsewhere, blowing sounds loud. Drum-like sounds on emphysema and
pneumothorax. Cyanosis. Lesions, depressed, flesh-like,
non-crepitating lobules or lobuletes, sink in water, dilatable.
Treatment, rouse respiratory centres, douches, cold and warm,
slapping, electricity, forced inspiration, diet, massage. Treat
attendant disease.
This has been already referred to as a result of bronchitis, but it
deserves special mention as a sequel of that affection, and in various
domestic animals, as an independent condition. The condition is one of
consolidation of lung by the complete exclusion of air, but without any
infiltration of its substance by inflammatory exudate or dropsical
effusion. The tissue remains in its normal state apart from the fact
that its bronchioles and air sacs are undilated. The affected portion
has a solid dark fleshy appearance. The collapsed portion often
represents one lobule or group of lobules which communicate with a
single bronchium.
_Causes._ In some instances the conditions remain from birth, the lobule
never having been called into use. This is seen especially in cattle and
other meat producing animals, in which active breathing is
systematically suppressed in the interests of rapid growth and the
deposition of fat. In the improved breeds the lungs remain larger than
the exigencies of the life demand, and large portions remain out of use.
In bronchitis the condition is acquired, and is mainly dependent on the
blocking of a bronchial tube with tenacious mucus or a desiccated mass.
The pathological lesions of bronchitis favor this since one of the
earliest changes in the inflamed mucosa is the desquamation of the
columnar epithelium. This removal of much of the cilia and the paralysis
of much of what is left annihilates for a time the normal method of
clearing away the secretion, and this being now produced in excess
blocks the tubes. This secretion virtually acts like a ball valve in
favoring the exit of the air during the convulsive expiration of
coughing, and hindering its entrance during the succeeding inspiration.
The bronchia and bronchioles decrease in size to near their termination,
so that, as forced out in coughing, the secretion enters the larger tube
and allows the exit of air, which as drawn back in inspiration it enters
the smaller tube and closes it against any possible ærial entrance.
Mendelssohn and Traube demonstrated this action by introducing a shot
into a dog’s lung, and in two days the left lung was found collapsed and
the right one the seat of complementary emphysema. The violence and
frequency of the cough therefore bears a ratio to the occurrence and
extent of atelectasis. Other causes are the compression of the lower
lobes of the lung by hydrothorax, by pneumothorax (developed by
lacerated lung or perforated chest wall) or by a false membrane
contracting in process of organization.
_Symptoms._ As a congenital condition in the improved meat producing
animals the condition is rarely recognized in life and cannot be said to
be a defect. The collapsed lobule being farther removed from the air may
be a more favorable field for the growth of pathogenic bacteria, but on
the other hand these do not so readily penetrate it as if the tubes were
open. When the collapse is more extensive, the contrast in the flatness
on percussion and indistinctness of the respiratory murmur on the
affected side, and the marked resonance and loud murmur on the other,
may serve to identify the affection. In extensive, traumatic cases this
contrast is much more prominently marked, as the expanded portions have
to take on extra compensatory work and are not infrequently rendered
emphysematous. The drum-like sound in percussion of such parts, and in
the upper part of the chest in pneumothorax are pathognomonic of these
conditions. Again in hydrothorax the horizontal upper level of the area
of dulness betrays a liquid cause. Severe cases are marked by cyanosis.
The _lesions_ seen in atelectasis consist in depressed areas of a dark
fleshy color on the surface of the lung, usually sharply limited by the
borders of the lobules, and in strong contrast with the bulging, light
colored lobules adjacent, which are often emphysematous. The collapsed
lobule may usually be dilated when air is forced into the bronchium, but
if it has been of some standing this is often difficult or impossible.
If it has resulted from bronchitis or compression of a previously
inflated lung it will often float in (not on) water, from a little
retained air, but in congenital atelectasis it is airless and sinks to
the bottom.
When _treatment_ is demanded it will vary according to the cause. In
congenital atelectasis the respiratory centres must be roused. The new
born animal may be sprinkled alternately with ice cold and hot water, or
the chest may be slapped with the palm of the hand or a wet towel. The
nostrils must be cleared of mucus, and the lungs inflated by blowing or
bellows, the larynx being pressed back against the gullet to prevent
inflation of the stomach. If available electricity may be applied to the
chest walls. These measures may be repeated at intervals and the
systemic weakness overcome by nourishing food, stimulants and friction
of the skin.
In acquired atelectasis we should seek to correct the disease to which
it owes its existence. In bronchitis the measures already indicated for
the liquefaction and removal of the expectoration will be in order; in
hydrothorax a judicious paracentesis and in pneumothorax the aspiration
of the gas, and the closure of any traumatic opening through which that
gas has gained access.