1911 Encyclopædia Britannica/Pneumonia

PNEUMONIA (Gr. πνεύμων, lung), a term used for inflammation of the lung substance. Formerly the disease was divided into three varieties: (1) Acute Croupous or lobar pneumonia; (2) Catarrhal or Broncho-pneumonia; (3) Interstitial or Chronic pneumonia.

1. Acute Croupous or Lobar Pneumonia (Pneumonic Fever) is now classed as an acute infective disease of the lung, characterized by fever and toxaemia, running a definite course and being the direct result of a specific micro-organism or micro-organisms. The micrococcus lanceolatus (pneumococcus, or diplococcus pneumonia) of Fränkel and Weichselbaum is present in a large number of cases in the bronchial secretions, in the affected lung and in the blood. This organism is also present in many other infective processes which may complicate or terminate lobar pneumonia, such as pericarditis, endocarditis, peritonitis and empyema. The bacillus pneumonia of Friedländer is also present in a proportion of cases, but is probably not the cause of true lobar pneumonia. Various other organisms may be associated with these, but they are to be regarded as in the nature of a secondary invasion. Lobar pneumonia may be considered as an acute endemic disease of temperate climates, though epidemic forms have been described. It has a distinct seasonal incidence, being most frequent in the winter and spring. Osler strongly supports the view that it is an infectious disease, quoting the outbreaks reported by W. L. Rodman of Frankfort, Kentucky, where in a prison of 735 inhabitants there were 118 cases in one year; but direct contagion does not seem to be well proved, and it is undoubted that the pneumococcus is present in the fauces of numbers of healthy persons and seems to require a lowered power of resistance or other favouring condition for the production of an attack.

Lobar Pneumonia begins by the setting up of an acute inflammatory process in the alveoli. The changes which take place in the lung are chiefly three. (1) Congestion, or engorgement, the blood-vessels being distended and the lung more voluminous and heavier than normal, and of dark red colour. Its air cells still contain air. (2) Red Hepatization, so called from its resemblance to liver tissue. In this stage there is poured into the air cells of the affected part an exudation consisting of amorphous fibrin together with epithelial cells and red and white blood corpuscles, the whole forming a viscid mass which occupies not only the cells but also the finer bronchi, and which speedily coagulates, causing the lung to become firmly consolidated. In this condition the cells are entirely emptied of air, their blood-vessels are pressed upon by the exudation, and the lung substance, rendered brittle, sinks in water. The appearance of a section of the lung in this stage has been likened to that of red granite. It is to the character of the exudation, consisting largely of coagulable fibrin, that the term croupous is due. (3) Grey Hepatization. In this stage the lung still retains its liver-like consistence, but its colour is now grey, not unlike the appearance of grey granite. This is due to the change taking place in the exudation, which undergoes resolution by a process of fatty degeneration, pus formation, liquefaction and ultimately absorption—so that in a comparatively short period the air vesicles get rid of their morbid contents and resume their normal function. During resolution the changes in the exudate take place by a process of autolysis or peptonization of the inflammatory products by unorganized ferments, absorption taking place into the lymphatics and circulation. The absorbed exudate is mainly excreted by the kidneys, excess of nitrogen being found in the urine during this period. This is happily the termination of the majority of cases of lobar pneumonia. One of the most remarkable phenomena is the rapidity with which the lung tissue clears up, and its freedom from alteration or from infiltration into the connective tissue as frequently takes place after broncho-pneumonia. When resolution does not take place, death may occur from extension of the disease and subsequent toxaemia, from circulatory failure, from the formation of one or more abscesses or more rarely from gangrene of the lung or from the complication mentioned below. Chronic interstitial pneumonia is infrequent, following on the acute variety. The most frequent seat of pneumonia is the base or lower lobes, but occasionally the apices are the only parts affected. The right lung is the most often attacked. Pneumonia may extend to the entire lung or it may affect both lungs. The death rate of acute lobar pneumonia in the chief London hospitals is 20%. With an organism so prevalent as the pneumococcus it follows that alcoholism, diabetes and other general diseases and intoxications must render the body liable to an attack. Males are more commonly attacked than females, and a previous attack seems to give a special liability to another. The incubation period of pneumonia is unknown; it is probably very short.

The symptoms are generally well marked from the beginning. The attack is usually ushered in by a rigor (or in children a convulsion), and the speedy development of the febrile condition, the temperature rising to a considerable degree—101° to 104° or more. The pulse is quickened, and there is a marked disturbance in the respiration, which is rapid, shallow and difficult, the rate being usually accelerated to some two or three times its normal amount. The lips are livid, and the face has a dusky flush. Pain in the side is felt, especially should any amount of pleurisy be present, as is often the case. Cough is an early symptom. It is at first frequent and hacking, and is accompanied with a little tough colourless expectoration. which soon, however, becomes more copious and of a rusty red colour, either tenacious or frothy and liquid. Microscopically this consists mainly of epithelium, casts of the air cells and fine bronchi, together with granular matter, blood and pus corpuscles and haematoidin crystal. The micro-organisms usually present are the pneumococcus, Friedländer’s bacillus, and sometimes the influenza bacillus. The following are the chief physical signs in the various stages of the disease. In the stage of congestion fine crackling or crepitation is heard over the affected area; sometimes there is very little change from the natural breathing. In the stage of red hepatization the affected side of the chest is seen to expand less freely than the opposite side; there is dullness on percussion, and increase of the vocal fremitus; while on auscultation the breath sounds are tubular or bronchial in character, with, it may be, some amount of fine crepitation in certain arts. In the stage of grey hepatization the percussion note is still dull and the breathing tubular, but crepitations of coarser quality than before are also audible. These various physical signs disappear more or less rapidly during convalescence. With the progress of the inflammation the febrile symptoms and rapid breathing continue. The patient during the greater part of the disease lies on the back or on the affected side. The pulse, which at first was full, becomes small and soft owing to the interruption to the pulmonary circulation. Occasionally slight jaundice is present, due probably to a similar cause. The urine is scanty, sometimes albuminous, and its chlorides are diminished. In favourable cases, however severe, there generally occurs after six or eight days a distinct crisis, marked by a rapid fall of the temperature accompanied with perspiration and with a copious discharge of lithates in the urine. Although no material change is as yet noticed in the physical signs, the patient breathes more easily, sleep returns, and convalescence advances rapidly in the majority of instances. In unfavourable cases death may take place either from the extent of the inflammatory action, especially if the pneumonia is double, from excessive fever, from failure of the heart's action or general strength at about the period of the crisis, or again from the disease assuming from the first a low adynamic form with delirium and with scanty expectoration of greenish or “ prune juice " appearance. Suc cases are seen in persons worn out in strength, in the aged, and especially in the intemperate.

The complications of acute pneumonia are pleurisy, which is practicaily inevitably present, empyema (in which the pneumococcus is frequently present and occasionally the streptococcus), pericarditis and endocarditis, both due to septic poisoning, while perhaps the most serious complication is meningitis, which is responsible for a large percentage of the fatal cases. The pneumococcus has been found in the exudate. Secondary pneumonias chiefly follow the specific fevers, as diphtheria, enteric fever, measles and influenza, and are the result of a direct poisoning. Bacteriologically a number of different organisms have been found, together with the specific microbe of the primary disease; the striking features of primary lobar pneumonia are often masked in these types.

The treatment of acute pneumonia has of late undergone a marked change, and may be divided into 3 heads: (1) General hygienic treatment; (2) the treatment of special symptoms; (3) treatment by vaccines and sera. The same treatment of absolute rest should be carried out as in enteric fever; this absolute rest is necessary to limit the auto-inoculation by the absorption of toxins. Fresh air in abundance and even open air treatment if possible has been attended with good results. Ice poultices over the affected part are useful in the relief of pain, while tepid sponging and tepid or even cold baths may be freely given, and the patient's strength supported by milk, soups and other light forms of nourishment. Stimulants may be called for, and strychnine and digital in are the most valuable; disinfection of the sputum should be systematically carried out. Many trials have been made with antipneumococcic serum, but it has not been shown to have a very marked effect in cutting short the disease. The polyvalent serum of Römer has given the best results. Much more favourable results have been obtained from the use of a vaccine. The results of vaccine treatment obtained by Boellke in 30 cases of severe pneumonia and one case of pneumococcic endocarditis are encouraging. The vaccine, to produce the best effects, should be made from the patient's own pneumococcus, as it is evident there are different strains of pneumococci, the doses (5 to 50 million dead pneumococci) being regulated by the guidance of the opsonic index. The objection to the preparation of the vaccine from the patient's own organisms is the time (several days) which is required, valuable time being thereby lost; but the results are much more certain than with the use of a “stock” vaccine.

2. Broncho-Pneumonia (Catarrhal or Lobular-Pneumonia or Capillary Bronchitis). An acute form of lobular pneumonia has been described, having all the characters of acute lobar pneumonia except that the pneumonia patches are disseminated. The term “broncho-pneumonia” is however here used to denote a widespread catarrhal inflammation of the smaller bronchi which spreads in places to the alveoli and produces consolidation. All forms of broncho-pneumonia depend on the invasion of the lung by micro-organisms. No one organism has however been constantly found which can be said to be specific, as in lobar pneumonia; the influenza bacillus, micrococcus catarrhalis, pneumococcus, Friedländer's bacillus and various staphylococci having been found. John Eyre, in Allbutt’s System of Medicine, gives 62% of mixed infection in the cases investigated by him. Broncho-pneumonia may occur as an acute primary affection in children, but is more usually secondary. It may be a sequence of infectious fevers, measles, diphtheria, whooping cough, scarlet fever and sometimes typhoid fever. In these it forms a frequent and often a fatal complication. The large majority of the fatal cases are those of early childhood. In adults it may follow influenza or complicate chronic Bright's disease or various other disorders. Broncho-pneumonia also may follow operations on the mouth or trachea, or the inhalation of foreign bodies into the trachea It is a frequent complication of pulmonary tuberculosis.

The following changes take place in the lung: at first the affected patches are dense, non-crepitant, with a bluish red appearance tending to become grey or yellow. Under the microscope the air vesicles and finer bronchi are crowded with cells, the result of the inflammatory process, but there is no fibrinous exudation such as is present in croupous pneumonia. In favourable cases resolution takes place by fatty degeneration, liquefaction, and absorption of the cells, but on the other hand they may undergo caseous degenerative changes, abscesses may form, or a condition of chronic interstitial pneumonia be developed, in both of which cases the condition passes into one of pulmonary tuberculosis. Evidence of previous bronchitis is usually present in the lungs affected with catarrhal pneumonia. In the great majority of instances catarrhal pneumonia occurs as an accompaniment or sequel of bronchitis, either from the inflammation passing from the finer bronchi to the pulmonary air vesicles, or from its affecting portions of lung which have undergone collapse.

The symptoms characterizing the onset of catarrhal pneumonia in its more acute form are the occurrence during an attack of bronchitis or the convalescence from measles or whooping cough, of a sudden and marked elevation of temperature, together with a quickened pulse and increased difficulty in breathing. The cough becomes short and painful, and there is little or no expectoration. The physical signs are not distinct, being mixed up with those of the antecedent bronchitis; but, should the pneumonia be extensive. there may be an impaired percussion note with tubular breathing and some bronchophony. Dyspnoea may be resent in a marked degree; and death frequently occurs from paralysis of the heart. Broncho-pneumonia is a serious disease, the death-rate in children under five has been estimated at 30 to 50%.

The treatment of broncho-pneumonia is mainly symptomatic. At the outset a mild purgative is given, and should the secretion accumulate in the bronchial tubes an emetic is useful. Inhalations are useful to relieve the cough, and circulatory stimulants such as strychnine are valuable, together with belladonna and oxygen. When orthopnoea and lividity are present, with distension of the right heart, venesection is necessary. The treatment of broncho-pneumonia by serum and vaccines is not so successful as in lobar pneumonia, owing to the difficulty of ascertaining the precise bacterial infection. The great danger of broncho-pneumonia is the subsequent development of pulmonary tuberculosis.

3. Chronic Interstitial Pneumonia (Cirrhosis of the Lung) is a fibroid change in the lung, chiefly affecting the fibrous stroma and may be either local or diffuse. The changes produced in the lung by this disease are marked chiefly by the growth of nucleated fibroid tissue around the walls of the bronchi and vessels, and in the intervesicular septa, which proceeds to such an extent as to invade and obliterate the air cells. The lung, which is at first enlarged, becomes shrunken, dense in texture and solid, any unaffected portions being emphysematous; the bronchi are dilated, the pleura thickened, and the lung substance often deeply pigmented, especially in the case of miners, who are apt to suffer from this disease. The other lung is always greatly enlarged and distended from emphysema; the heart becomes hypertrophied, particularly the right ventricle; and there may be marked atheromatous changes in the blood vessels. Later the lung becomes converted into a series of bronchiectatic cavities This condition is usually present to a greater or less degree in almost all chronic diseases of the lungs and bronchi, but it is specially apt to arise in an extensive form from pre-existing catarrhal pneumonia, and not infrequently occurs in connexion with occupations which necessitate the habitual inhalation of particles of dust, such as those of colliers, flax-dressers, stonemasons, millers, &c., to which the term pneumonokoniosis is now applied (including anthracosis, siderosis, chalicosis and the so-called “grinder’s rot”).

The symptoms are very similar to those of chronic phthisis (see Tuberculosis), especially increasing difficulty of breathing, particularly on exertion, cough either dry or with expectoration, sometimes copious and fetid. In the case of coal-miners the sputum is black from containing carbonaceous matter. The physical signs are deficient expansion of the affected side—the disease being mostly confined to one lung—increasing dullness on percussion, tubular breathing and moist sounds. As the disease progresses retraction of the side becomes manifest, and the heart and liver may be displaced. Ultimately the condition, both as regards physical signs and symptoms, takes the characters of the later stages of pulmonary phthisis with colliquative symptoms, increasing emaciation and death. Occasionally dropsy is present from the heart becoming affected in the course of the disease. The malady is usually of long duration, many cases remaining for years in a stationary condition and even undergoing temporary improvement in mild weather, but the tendency is on the whole downward.

See Allbutt and Rolleston, System of Medicine (1909); R. W. Allen, Vaccine Therapy and the Opsonic Method of Treatment (1908); Osler, Practice of Medicine (1909); The Practitioner (May 1908); Clinical Journal (Jan. 1908); American Journal of the Medical Sciences (Jan. 1908); W. C. Bosanquet and J. Eyre, Serums, Vaccines and Toxines (1909).