Infection and Defence of the Respiratory Tract

Kai Tiaki : the journal of the nurses of New Zealand, Volume XXII, Issue 3, 1 July 1929, Page 111

Infection and Defence of the Respiratory Tract

J. HARDIE NEIL

(By

M.8., Auckland.)

(Continued from April Number.)

What methods are there of increasing the bactericidal power of the blood? 1. By increasing the bacteria disabling power of the serum. Vaccines which are mixtures of killed bacteria and their toxins or poisons, can raise the bactericidal power of the blood against that particular organism. There are as before stated so many organisms, including the influenza virus, that can initiate an acute Rhinitis or a " cold" that immigation is most difficult, but the Streptococcus and pneumococcus are readily isolated and cultivated. Properly selected and prepared their vaccines are very efficient m the lessening or prevention of the lung complications that are of paramount importance. Tuberculin, which is a vaccine, m minute doses increases that power. 2. By increasing the number of Leucocytes. If the leucocytes are removed from the blood its bactericidal power is lost. If leucocytes are separated out of some blood and added to other blood the bactericidal power of the latter is correspondingly increased. Infection naturally causes an increase of the number of leucocytes. The administration of yeast and allied substances increases the quantity, but, unfortunately, not the quality, of the leucocytes. Blood transfusion from a healthy person as donor is often very efficient. Exposure to sunlight and to the arc-lamp is very helpful, but by overdoing it a distinct lowering may be brought about. Chemical Means to Aid m the Destruction of Bacteria m the Blood. 1. Substances acting directly on Bacteria. The newer arsenic compounds such as 606 are very effective against certain organisms, but not against common bacteria. A common antiseptic such as carbolic acid may be mentioned as typical of all the antiseptics commonly used. In weak solution, diluted with normal saline

solution, it had no action on either the bacteria or the leucocytes. In stronger solutions it destroys the lecocytes but not the bacteria. In very strong solution it kills both bacteria and leucocytes. Some of the newer dyestuff antiseptics such as flavine are effective m the destruction of bacteria, but unfortunaely they disappear from the blood very quickly. Arsenic preparations have a decided action on one variety of the streptococcus and remain some time m the blood, so that we may look forward to the discovery of chemicals effective against particular bacteria. Drugs acting indirectly as antiseptics on the bacteria so that they may be more easily and successfully attacked by the leucocytes. Perchloride of mercury has an undoubted action if the bacteria are m small amounts; 1-| drachms of 1-1000 diulted with two ounces of saline, injected slowly, once daily for three or four days. Drugs which Increase the General Bactericidal Power of the Blood. Hyper tonic, or stronger than normal, salt solution possesses this power against all organisms, and m appropriate doses, H-2i ounces of a 10% solution intravenously, will raise and maintain it for 24 hours. Natural Antiseptic Power cf the Blood. It is generally thought that the naturally occurring bactericidal agencies are weak when contrasted with chemical antiseptics, but that is not so. A culture plate of ordinary media or laboratory food for bacteria may be taken, and discs of it removed. In the cavities thus produced, discs of blotting-paper, soaked m antiseptics or body fluids, are placed. They are covered again by the melted media, and then a layer of the media is poured over the whole surface of the plate. A culture of an ordinary microbe is planted over it, and after incubation it

will be seen that the tears and mucus are effective to stop growth, but carbolic acid, five per cent. ; mercuric chloride, 1-1000; flavine, 1-1000; mercurochrome, 1-100; gentian violet, 1-100; have no effect.

We have now discussed the defensive power of the mucous membrane and of the blood, stressing the important bactericidal power of the white blood cells of the latter. The lymphatic system consists of a series of channels which collects the lymph from the various tissues of the body and returns it to the large veins m the neck, where it mixes with the blood. In the course of the lymph vessels are various aggregations of lymphoid or adenoid tissue called lymph nodes, or glands. They are practically filtration stations. In certain places they are so large as to form so-called lymph organs. namely: the tonsil, the spleen, and the thymus.

These nodes or glands contain cells indistinguishable from the lymphocytes of the blood. Enmeshed m supporting tissue, they occur abundantly m practically all body tissues, where they seem to form a secondary drainage system and a multitudinous series of outposts for destruction of invading organisms and infected tissues.

Besides being present m all mucous membranes, lymphoid or adenoid tissue is massed m certain places m the upper respiratory tract. It forms a continuous ring, Waldeye's, at the back of the nose and pharynx. In the naso pharynx it is called the adenoids. It is continued as a band down the side wall, and continued on to the space between the two pillars of the palate, where it forms the tonsils. It is then continued to the back of the tongue, forming the lingual tonsil. The tonsil can be described as an open lymph gland; that is, masses of lymphocytes enmeshed m a supporting structure. The latter is condensed on the outside surface as a compact membrane or capsule, through which pass the arteries, veins, and lymphatics. Comparative anatomy shows that the space within the capsule is more or less filled with lymphoid or adenoid tissue. There is always an un-

filled portion known as the supertonsillar fossa, or pit. From the surface there are a number of tunnels or crypts that pass down nearly to the capsule. The skin of the inner throat surface is thin where it passes into the crypts, and allows the lymphoid structures to come close up to or be actually exposed on the surface.

The tonsil is most active during the active growing" period of childhood. It reaches its highest development m the mammals. Although it must have a function, this is by no means indispensable. as the other lymphatic masses are innumerable. Its function would be no more missed m removal than would the function of the skin be affected by the removal of a small area.

On the other hand, one is confronted by the fact that it is the main harbour and ideal breeding place for the streptococcus and pneumococcus. Bacteriological studies by many observers show that over fifty per cent, of apparently normal tonsils hold the dangerous variety of streptococcus, and that about forty per cent, contain the pneumonia organism.

The free blood supply to the tonsil shows the possibility of these organisms reaching the circulation. The tonsil is the inital site of attack of scarlet fever and diphtheria, and, unfortunately, after the acute infection has passed, 'retains them m the depths of its crypts, thus constituting the carrier station. It is thus a menace to others and to the patients themselves. The prolonged sojourn m the tonsils does not seem to diminish their virulence to any great extent. The cure of the nose and ear disease and especially of ear complications of scarlet fever is greatly facilitated by tonsil removal. It has always been known that exposure to cold and privation predisposes to sore throats, but investigations have proved that it has a distinct basis m fact. The chilling of the skin temporarily lowers the temperature of the unexposed tonsil as a result of temporarily diminishing and disturbing the blood supply. This permits the organisms present m the tonsil to grow rapidly with the production of inflammation.

It is impossible to avoid the conclusion after studying the voluminous statistics available that there is a distinct causal relationship between chilling of the skin and respiratory infections. The good effects on children who have suffered from sore throats, ear infections, and bronchitis troubles, and who have subsequently had their tonsils and adenoids removed, is well known. One of the most pleasing features to our mind is the comparative immunity it gives them to diphtheria and scarlet fever, m addition to the above-mentioned affections. A general experience is that such a child with a clean mouth practically escapes most of the infections of childhood or gets them only m a mild form. Other Sources of Infection. The mouth has a large and varied bacterial population varying with the cleanliness of the teeth and the vitality of the person. Its natural protection consists of a thick, dense mucous membrane on the gums, whilst over other parts, except the tongue, there is a very free mucous gland supply. Escape from infection is aided by the mass movement of the food and tongue, but another factor is the three pairs of salivary glands whose secretion varies m bactericidal potency m accordance with the health of the individual. The increase m the septicity of the mouth m those suffering from infection and bodily derangement is due to the lessened efficiency of the mucus m keeping down the mouth bacteria. The organisms find lodgment round the necks of the teeth and the gums. They may also lodge m the interstices of the mucous membrane, particularly at the margins of the gums, and also m the glands. Apart from the removal of masses of infected debris, cleansing of the mouth with antiseptics m general use is of little avail. They probably act by stimulating the blood supply of the mucous membrane during the rubbing action. Hacteriologically, very little effect on the bacterial population is noted after their use. Effective cleansing is by a brush and some substance containing chalk that acts as a mechanical cleaner m removing debris, particularly from the necks of the

teeth. The interstices also having been cleaned, use may be made of a saturated solution of 1 thymol. This was found by a Research Committee to be -followed by the greatest diminution of 'mouth bacteria. Milton, a proprietary ' article, a particularly stable form of" a chlorine compound, is also very effectual. 1 The mouth should be cleansed before' retiring to bed, as during sleep the bacteria get all their main requirements, viz. : food, moisture, warmth, and freedom from disturbance. .

For the cleansing and toning up of the gum margins, after the removal of tartar, the use of chalk paste and thymol (71 grains to the ounce,' with glycerine and tragacanth)i freely applied 'to the margins of the gums and allowed to remain overnight, is quite effective. Tartarus a calcerous deposit from the saliva, which becomes contaminated by bacteria and food debris. It separates the' gum ; from the necks of .the teeth, and' is a great source of infection to the mouth. The dangers of, mouth' infection are manifold. The absorption effects from the surface are not very great, but if infection passes dqw,n the root of a tooth and lodges round the, point or apex, the inability to escape from the surface causes absorption to take place through the jaw bone, the vessels of which give access to the circulation.

This may cause the lodgement of the bacteria m various p,arts of the system, setting up what is, called, focal infection. In reference to the cleansing of the mouth, one must refer to the necessary care of the tooth plates. They have microscopical fissures- and cracks that become infected by bacteria, fungi, debris and saliva which set up an irritant secretion. The plates cannot be cleansed by washing at night and then replacing them m the mouth before going to bed. Their retention does not affect the shape of the gums. They should be, brushed under a running tap with a simple tooth powder such as carbolic tooth powder, placed m a cup or glass, and covered with thymol water or a suitable antiseptic such as : 10 drops of Milton added to the covering water.

Among the other deleterious effects of mouth sepsis is the fact that it causes the pharynx to be septic, with possible contamination of the nose and ears. It may be so great m amount that on being swallowed it may overcome the resistance of the gastric juice, which is usually an efficient barrier, and cause a severe anaemia.

It menaces the lungs, as during sleep and deep anaesthesia. Some of the mouth secretions may trickle into the larynx and windpipe. Thus it very severely enhances the gravity of lung infections. One of its most important and menacing dangers is its almost invariable association with cancerous infection. Apparently the virus of cancer, which is present all over civilisation, finds m a septic mouth very favourable conditions for growth or activation of virulence. Cancer seems to effect a footing on areas subject to injury, or chronic sepsis, of the mucous membrane or skin. Areas that are covered by ciliated mucous membrane are rarely affected, the movement onwards preventing the "digging m" of local invasion. Frequent sites are places where the natural passes have constrictions, or localities where the secretions tarry. Thus it is common on the lips, tongue, palate, vocal chords, middle of the gullet m men and top of the gullet m women.

Some surgeons who do a large amount of abdominal surgery say : "No sepsis of the mouth, no malignant disease of the digestive track." In recent years the Journals are frequently noting the association of sepsis # of the mouth and malignancy. One of the foremost throat men m the States said m a recent Journal : 4t I have hardy ever seen a cancer of the mouth or throat m a patient who kept his mouth clean. As a rule, such patients have filthy mouths. They appear never to have used a toothbrush." Whatever the cause of cancer, the fact remains that a septic mouth is a distinct menace to health m general and that it facilitates invasion by. cancer.

The pharynx has a thick lining of mucous membrane, on a tough fibrous membrane basis. It is subject to tubercle cancer and specific disease, but apart

from a mild participation m nose and mouth inflammation, it generally escapes disease m spite of the stress to which it is subjected. During the act of swallowing the soft palate blocks the way to the nose, and the upper part of the larynx closes and shuts off access to the windpipe and lungs. Thus the pharynx acts as a bacterial trap between the nose and mouth and the larynx, directing material m it into the gullet.

The lower respiratory tract consists of the larynx, tranchea, with its two branches, the main bronchi, the smaller bronchi, and finally the air sacs m the lung tissue proper. It is lined, with the exception of the vocal chords and the air sacs, by a mucous membrane, which is very plentifully supplied with mucous glands and has cilia on its surface.

These cilia are particularly active and abundant on the posterior wall of the trachea. Normally, the mucus is lifted up to the opening of the larynx, where, by the swallowing movement, it is emptied into the pharynx, and swallowed. In experimental work, the cilia will move small fragments of blotting-paper upwards, and can actually be made to turn a very light wheel.

It can deal alone with a large amount of mucus put out by the multitudinous glands to keep the air passages moist. It is like a moving staircase, and it has been calculated that it moves particles at the rate of one inch a minute. Material from the smallest bronchi can be brought up unaided m a few minutes. Cough is not necessary to clear the air passages of the normal amount of secretion.

When people are dying the bubbling sounds heard are due to the accumulation of mucus m the lower part of the bronchial tree, owing to the failing ciliary action.

The second defensive mechanism is the cough reflex, which can be excited by any irritant or excess m the larynx of secretion, or m the tract below. " It is most effective m the larynx and trachea and affects the smaller bronchi very little.

The third protective mechanism is the peristaltic or wave-like successive contraction of a tube m one direction. This is very effective m the finer bronchi, and greatly assists by working up any masses of secretion. The clearing power of the lower air passages can be seen by experimens m the anaesthetised dog, which shows that even comparatively large foreign bodies can be got rid of without the explosive cough.

The fourth protective mechanism is the bactericidal power of the lungs, with its large and quickly changing blood content. The main protection of the lung, then, is the mucous membrane. Infective material getting across the trachea and bronchi may cause little or no trouble, but if by means of the circulation masses of bacteria such as emboli get access to the lung, intense inflammation at once sets m. The lower air tract has normally few microbes, as, when introduced into the bronchi, they persist only from seven to sixteen hours. Yet infection of the lung takes place, and the cause is almost invariably from downward infection. In acute cases, such as following a cold with influenza, it is again a question of the dosage and virulence of th'e infecting organisms, and the resistance of the individual.

The sequence of cold m the head, laryngitis, with its irritating cough and slight hoarseness, bronchitis, and, m some cases, pneumonia, is well recognised. Likewise m diphtheria, the successive atack on the tonsils, larynx and trachea is seen. Undoubtedly small amounts of secretion from the pharynx find their way down into the larynx and windpipe, possible during sleep or m sudden inspirations.

In exploration of the trachea after an anaesthesia, the secretion found is mainly saliva. The constant passage of pus from the nose into the pharynx m some persons allows infection of the bronchi with a resulting chronic purulent bronchitis. A patient whose pharynx has been rendered insensitive by a local

anaesthetic, with the consequent derangement of the swallowing mechanism, was given a dose of iodised oil to swallow. This substance, which causes a heavy dark shadow m X-ray pictures, was found to have passed down into the bronchi on the right side.

Finally, there is a most important line of defence, the value of which m keeping the enemy out of the inner lines is greatly enhanced by early adoption, and that is rest. Later conditions will enforce its use when the enemy may be well within the lines and all but essential movements are excluded when the hand-to-hand, or antidote versus toxin, fighting is taking place.

The body has naturally only a certain amount of energy available. * Normally, it is consumed by muscular exercise, working the heart, lungs and other vital systems. In addition, a proportion is available for the formation of antidotes to infection. During muscular exercises, substance:; that are practically poisons are formed m the muscles. They are excreted during rest. The body energy is heavily drawn on during infections to supply the necessary antibodies or antidotes, consequently the value of diminishing the other forms of energy consumption is obvious. Rest m bed is the most effective assistance m combating infections. Just as m typhoid the cases which have carried on their ordinary occupations during the early stages are among the most serious, so m influenza and respiratory infections the person who " carries on " is heavily handicapping the body when all the energy not required for vital processes should be available to combat the infection.

The lesson suggested by our remarks is that infection of the respiratory tract may occur from epidemic infection, with organisms of increased virulence — but most infections occur from causes activating organisms alrealy m the* nose, mouth and pharynx, and that a clean mouth, a clean pharynx and general good hygiene minimise the possibilities of infection,