The Filtration of the Air.
As mentioned, at the opening of the supply pipe, a double thickness of ordinary gauze was stretched and this was changed at intervals. The principal filtration, however, was done in the small metal box at the side of the incubator which had a lid and through which the air passed before it entered the incubator (Fig. 5). A wad of cotton in the pipe or even in the box was uncertain for if well packed it seriously interfered with the ingress of air. I finally decided on a thin layer of cotton which, between two layers of gauze, was placed over the opening of the box that led the air into the incubator. This gauze filter was held in place by strips of adhesive plaster and was changed every other day; on very warm days when the air supply was poor this filter had to be removed during the heat of the day.
A very thorough filtration of the air is impossible without using considerable force back of the air current and we cannot depend on ordinary filtration to remove bacteria, hence it is more important that the source of the air be from the outside.
The heat supply was controlled by a thermoregulator in the upper rear corner of the incubator chamber. A hollow tin disk filled with ether pressed upon an iron pin which passed through a soft rubber disk into the opening which admitted the gas (Fig. 6). As the incubator became warmer the disk expanded and forced the point of the pin into the opening and thus cut off the gas supply. Theoretically it seemed a very simple and ideal thermostat, but practically the stability of the whole heating apparatus had much to be desired. We were not able to dispense with constant intelligent supervision of the heating apparatus, although the thermoregulators could be depended upon to turn down the gas flame when the incubators became too warm. The causes which forced us to supervise the heating and air supply will be discussed below.
The air supply, although forced downward by a fan, was by no means constant. There was a marked variation in the velocity with which it flowed through the incubators. On cool days, when the ratio of the atmospheric temperature and the incubator was 1 to 2 or 1 to 3, the anemometors rotated at a furious rate, but when the ratio rose to 3 to 4 or even 4 to 4, the circulation became poor. The hottest incubator had the most rapid circulation. When the outside air became warmer than the incubator the fan did not seem to be sufficiently powerful.
These difficulties were met in various ways. A too rapid circulation of air was moderated by increasing the thickness of the filtering gauze by a layer of cotton; sometimes the supply pipe was plugged in addition with a loose wad of absorbent cotton. When the air circulated too freely the difficulty of maintaining a constant high temperature was incurred; hence, as the external temperature fell near or below 40° some resistance to the intake of air was necessary in certain incubators.
When the outside air was very warm and the circulation of air correspondingly poor, all internal resistance to the flow of air had to be removed. On very warm days even a double layer of ordinary gauze could not be used for filtration purposes. Filtration of the air in the incubators had to be entirely discontinued on certain days, and the air supply of incubators not in use was shut off by tightly plugging the supply pipe; in this way the air supply in the incubators in use was correspondingly enlarged and the little fans were kept whirling at a rapid rate. The rapidity of the inflow was indicated by these fans, and our rule was that the fans should rotate just sufficiently rapid so that the individual blades of the fans were barely discerned and not so rapid as to make it appear as a single disk.
Another difficulty arose from the fact that the electricity from some reason had to be shut off during the night for a short time, but with the exception of a few very warm nights the circulation was sufficient. This defect of having the power shut off at night was finally remedied.
Theoretically it seems proper to get the air supply from the roof, but as this makes a long shaft which has great "drawing" power difficulties will arise. It takes a tremendous power to force hot air downward, and when the air is cold it is forced downward by its own weight, displacing the hot air. The long vertical pipe, therefore, is very objectionable. It is better to obtain the air from the outside at a level or very little above the top of the incubator; in this way there will be less trouble with the velocity of air through the supply pipes.
The importance of having the incubators always at the temperature desired or at least at a constant temperature is self-evident, but even with the elaborate mechanism employed the incubators required intelligent supervision. Our nurses could not go to sleep for three hours and be awakened by the watchman as they seemed to have done in London.
In the first place the gas pressure in the supply pipes was very inconstant, so that on different days or different periods in the day the flames in the Bunsen burner were different in size. Especially in the evening when the many restaurants and other places using gas for heating and other purposes had all their burners in use, the gas pressure became so low that the flames with the gas turned on to its fullest extent were too small to keep the water in the heating coil near the boiling point, which would often be necessary in the evening. Many attempts were made to rectify this deficiency in the gas pressure. The Concession Company even purchased an expensive gas pump, which proved unsuccessful because it failed to work at times and, therefore, had to be cast aside. Fortunately the gas company in the last two months in some way increased the general gas pressure which remedied the defect during our coldest weather (October and November). Again, when the air outside was near the freezing point the air would enter too rapidly and cool the incubator; this was remedied by increasing the filtration cotton. When the gas flames were too small alcohol lamps had to be used to raise the temperature of the water in the heating coil; or water was boiled on the gas stove and the boiling water poured into the coil. Most valuable, however, in overcoming these deficiencies of heat was the thermophere. Whenever an incubator began to go down in temperature in spite of the gas turned on full, a thermophere, several of which were always ready in boiling water, was placed in the compartment beneath the baby. This is an admirable way in making up the deficiencies in heat.
But we had trouble in another way. In hot weather the incubators would get too hoot. This was no fault of the thermoregulator but must be charged to the extreme fluctuations in temperature of the outside air. In a climate like St. Louis where the terrestrial temperature may vary 20° in a few hours, and the air is taken from the outside, no thermoregulator ever invented can be adequate. I need give only one example: The outside temperature one morning was 70° F. At noon the thermometer registered 95° in the shade. In the morning heat had to be applied to the incubators, and about 11 o'clock the thermoregulators turned the gas down, and it was turned entirely off by the nurses. At 12 o'clock noon, in spite of the fact that there had been no artificial heat for an hour, the temperature in the incubators was exceeding the prescribed upper limit, and the hot water was taken out of the coils; but the temperature still went up and iced water had to be poured into the heating coils of some of the incubators. To prescribe a temperature of 84° and to have the air streaming in at 95° gives the opportunity of making a refrigerator out of an incubator. This opportunity arose several times last summer.
It will be seen that the difficulties were such as to necessitate a constant supervision, and I feel that no sort of a machine can replace intelligent watchfulness when it comes to rearing premature infants. This supervision is furthermore necessary because the incubator's temperature was often changed according to the needs of the infant.
There can be no doubt that the principal cause of the variation in heat is the inflow of air from the outside. In a changeable climate it seems best not to obtain the air directly from the outside, but it should first pass through a large chamber in which its abnormal condition is modified.
We tried to maintain the humidity at about 60 per cent, but the variations were extreme in spite of care. In warm weather with rain outside it often rose to 90 per cent; when the air was dry and cold outside it would fall as low as 10 per cent. The pan of water in the drawer in situated below the water coil and therefore its evaporation is too slow. By placing wet cotton or twisted gauze in a beaker in the side box an additional moisture could be obtained, but all this was insufficient in cold weather.
The best way to raise the humidity rapidly is to pour hot water in the evaporating pan, but as soon as the water cooled the humidity dropped again.
The trouble with the humidity again depended on the fact that the air was received from the outside.
Considerable relief was obtained when the electric coil in the large inlet pipe was hot and moistened cotton was put in the small air box at the side of the incubator. I do not see how an incubator could be constructed to remedy this entirely.
In a restricted sense, the term hospitalism is applied to a species of intoxication found in infant asylums and characterized by fatal malnutrition, atrophy and death. In another sense it has been used to designate the poor resisting power of such infants to all infectious processes. In a wider sense it signifies the aggregate of etiological factors which cause such an enormous death-rate in all infant asylums and hospitals. It is in this wider sense that the term is used here.
It is well known that the death-rate in foundling asylums ranges from 35 to 80 per cent., enormously exceeding the mortality of infants in homes. The causes which lead to this are various but, as a rule, the high death-rate is principally attributable to the introduction of some pathogenic organism and its dissemination among the infants. Now, the same factors which cause this morbidity and mortality in foundling asylums are very prone to be operative in an incubator institute. Hence, to whatever difficulties may be encountered in rearing the babies on account of their premature birth, are added the great dangers of keeping many babies together and nursed by the same individuals.
The death-rate, therefore, in such an institution will always be much higher than the death-rate of such babies in private practice. So I am not at all convinced that such institutions are a blessing. There are death-dealing causes connected with such an institution that are extremely difficult to overcome.
It was hospitalism that made the mortality so high before I took charge, and it was operative for some time even after radical changes were made in the management. Its inception began with a very sick baby which was obtained from a foundling home. Following its arrival the mortality rapidly increased. Some blunder in the milk supply added another infection and enteritis and marasmus carried the infants off. It is rather significant that the symptom of hospitalism arose after a baby was obtained from a foundling home.
The prevention of hospitalism then is the first duty of an incubator institute and it takes money, great care and well-trained nursing to accomplish this.
In the first place no infant should be admitted that is several days old and shows some gastrointestinal or any other infection. I consider the admission of a sick baby from a foundling home several days old as the greatest mistake of the former management.
In the second place, only mother's milk should be fed to incubator babies, and even "graduates" must obtain a mixed feeding. At least mother's milk confers an immunity to infection on young babies which can not be supplied by any modification of cow's milk.
The most rigid asepsis must be practiced in regard to everything that enters the mouth of the infant. Sterilization and cleanliness are absolutely necessary. No nurse who takes care of an infected baby, however mild it seems, should at the same time care for a well baby.
A recent valuable contribution on the subject of the arrangement of an infant hospital is by Klautsch. -- Archiv Kinderheilkunde, Vol. 39.
The frequent disinfection of the incubators has been especially insisted upon by Budin. The Kny-Scheerer incubator is well made for thorough disinfection. It can be washed and an antiseptic applied; as to the antiseptic to be used little is found in literature. After Bertin insisted that incubators may serve as a source of infection and must be so constructed in order that they may be disinfection, Lion fulfilled the requirements, and an incubator was constructed that could be sterilized by dry heat or steam; but this can not be done very often unless special provisions for this has been made. Hence, I had to select antiseptics. I rejected formaldehyd for the simple reason that the irritating fumes which emanate from the disinfected surfaces might prove injurious to the infant. While its occasional application to an incubator in which the infected infant happens to be placed, may be recommended, as a disinfectant for daily use it has serious objections. For a different reason corrosive sublimate could not be used, since its corrosive effect on nickel plate and iron is too well known. On the other hand, carbolic acid or tricresol have not these disadvantages, but as some of these antiseptics must adhere to the crevices and be gradually evaporated it might prove deletorious. Most of the ordinary antiseptics proving objectionable, alcohol in a strength of 70 per cent was chosen as the safest disinfection; this seemed ideal, especially as Harrington's recent experiments were fresh in mind. Each day everything was removed from the incubators and the inside given a thorough wiping with a moist cloth. This was followed every other day by a careful sponging of all metallic and glass surfaces with 70 per cent alcohol; a few minute's airing sufficed to get rid of the alcoholic vapor. No infection was traced to the incubators during my service.
As to the attempt of disinfecting the air, here and there hinted at in literature, it is only mentioned to be pronounced ridiculous. The use of sulphuric acid to dry and cleanse the incoming air also is useless and not devoid of danger.
The most iron rules must be laid down to prevent microbic infection. Each infant must have its own thermometer, bottle and clothing. For various reasons this rule could not always be followed; but the thermometers were kept in a sublimate solution and rinsed immediately before using. The bottles and nipples were thoroughly boiled between each feeding and an additional supply constantly kept on hand in a solution of boric acid, and were washed in sterile water before using. No diaper was used a second time. For the same reason it is dangerous to apply several babies in succession to the same wet nurse; the disinfection of the nipple is by no means easy. Thrush and mild gastrointestinal infection can arise in this way. The wet-nurses' nipples were disinfected with dilute alcohol or boric acid solution.
The most dangerous and, as it proved, the most certain means of conveying infection is the nurse's finger; without conscientious, trained nurses, accidents will happen. With each baby there is a possibility of introducing some new pathogenic micro-organism, and sometimes even before it is recognized another baby may be infected from this. Every newcomer must be carefully watched for several days as to the appearance of infected eyes, mouth or umbilicus.
By our means an infection was practically excluded. One baby developed furuncles; the same trouble appeared in others, and when I took charge, by rigid isolation of all clothing a further spread was checked and healing took place under treatment. The mouth was the most common seat of infection and our attention must be especially laid upon this port of entry.
In all such institutions the well must in every way be entirely separated from the sick and provisions for this separation must be supplied.
There seems no good reason why premature infants should not be clad as other infants; they should be warmly clad even in an incubator. It is a mistake to depend entirely on superheated air to prevent the loss of heat. The inhalation of such hot air neither stimulates respiration or metabolism and favors infection; hence, we should depend in a great measure on good clothing to lessen heat radiation from the body. Too much clothing in the very feeble necessitates too much manipulation, and still we adhered to the old custom of wrapping them in cotton, but this was adhered to for a short time only (one or two weeks), when the ordinary clothing of infants was placed upon them.
The subjoined halftone (Fig. 7) illustrates the articles of clothing for a premature infant: a soft woolen shirt, a diaper, flannel band, cotton and a covering of gauze in which the body is wrapped. Eross was probably correct in attributing little warmth to these envelopes of cotton -- loose cotton is not warm. A soft light woolen blanket would really seem preferable in private practice, or lamb's wool should be used instead of cotton. We recall one instance where a father bought a premature infant safely to the incubators which had been wrapped in absorbent cotton and then enveloped in several thicknesses of a blanket. It would seem safer to substitute some thick woolen goods for the gauze to be used over the cotton. The diaper in all cases consisted of a layer of absorbent cotton and sterilized gauze (Fig. 8). Every morning and evening enough of these diapers were made for half a day. As soon as they were wet or soiled they were discarded and burned. When it is known that we used about $5.00 worth of sterilized gauze daily just to make napkins it will be seen what expense is found in such an institution. In no case was it permissible to change the diaper of one baby for that of another when slightly wet and then dried.
Long knit socks or stockings were put on all infants which were pinned to the diaper in the usual way.
Ballentine [sic] (British Medical Journal, May 17, 1902), Rotch and others declare that premature babies should be kept in darkness. On the contrary, our babies were kept constantly in the light; for, as mentioned, light was necessary to show the incubators and at night it was necessary to permit of their care. While the light was much subdued after 11 p.m. the infants were never in darkness. I was unable to discover any harmful effects of this light.
Even the youngest infants should have their arms out so that it can move them; this permits a little motion and assists the respiration and circulation.
The question of bathing like so many questions concerning premature infants is considered from a different standpoint by each author. Some interdict bathing for the first week or ten days, while others recommend its daily use. Rotch says that the premature infant should not be bathed but should be rapidly covered with warm sweet oil and wrapped up in absorbent cotton; this is changed only every forty-eight hours, when the infant is again covered with oil. Voorhees gives very similar directions. Monti recommends that premature infants be bathed at once after birth in water at a temperature of 29 to 30° R. (about 98° F.). He furthermore believes that sponging the baby once or twice daily is very advantageous as a circulatory stimulant. Parts of the infant are successively exposed and washed with sterilized cotton dipped in warm water; a mild soap can be used. This stimulates the function of the skin and prevents infection. Blair also finds daily repeated baths helpful to stimulate the circulation and the skin. Budin is an ardent advocate of daily bathing in warm water, but he finds it especially of service in those infants whose temperature remains below normal. Finkelstein has likewise corroborated the value of bathing.
For the purpose of increasing the rectal temperature Budin advises two procedures: Where a rapid elevation of the temperature is desired the infant is plunged into a bath at a temperature of 37° C. and remains there until its temperature is normal. However, he finds that if the infant is placed in the bath at a temperature of 1° above the infant's rectal temperature and then gradually raised during fifteen or twenty minutes until it reaches 37° C. the infant's rectal temperature will remain normal much longer than when raised rapidly by the former method. The temperature of the water is elevated by the addition of warm water which should be poured into a funnel to which a tube is attached which reaches below the surface of the water in the bath tub. If the water is gently poured into the tub the warmer water has a tendency to float on top and does not mix with the cooler water.
We followed Rotch's directions in the main. The infant was rubbed with oil and placed at once in the incubator. The baby was not bathed for several days, when a daily sponge was begun; this was done with sterilized cotton, one part after another being exposed; after this it was given an oil rub. In several instances a warm bath was given when the infant's temperature fell below 96° F. For rapid elevation of the rectal temperature the warm bath is the ideal method and should always be resorted to.
I shall have to obtain more evidence than I possess at present to believe that this frequent bathing is necessary. Of course, when the temperature of the incubator is kept too high, as Blair's figures evidently are, or if the incubator temperature is kept too low as Budin evidently does, at least for infants weighing less than 1200 grams, these baths must be absolutely necessary; in one case to cool the infant and in the other case to heat the infant. But if the infant's rectal temperature is maintained between 97 and 98° F., bathing will be found unnecessary. A daily sponge and afterward a good rub with oil will usually be found sufficient. If the baby's temperature is below 96.5° or above 100° F. the bath should be given.
There is, however, one possible advantage of frequent bathing during the first few days of life and that is that the skin has an opportunity to imbibe water, for usually an insufficient supply of water is given during the first few days. Still, as it will be found easier to give the same amount of water by the stomach or rectum this advantage is not worth considering.
Many authors do not mention the oil rub. Some seem to think it unnecessary, others believe it is a mistake to use it, still others recommend it. It is difficult to conceive any serious objections to it. As massage is so helpful it is really necessary to have some emollient for massage on the dry tender skin. Furthermore it protects the sensitive skin somewhat from irritation, and as a means of cleansing it should by no means be despised. Then there are two specific reasons which, therapeutically at least, should be given due consideration.
First, the oiled skin prevents a too rapid heat loss, the oil acting as a non-conductor, and, finally, the oil prevents to some extent the evaporation of water, which in a warm incubator should always receive attention. In fact, the rapid loss in water is one of the most serious menaces to the life of the infant.
Just what oil should be used is somewhat indefinite. Probably any non-irritating oil will answer. We used olive oil, Rotch recommends sweet oil. An animal fat would seem to be preferable, so that fresh lard or fresh butter might be used; the tendency of the latter to become rancid will, no doubt, be a serious objection. Cocoanut butter should also be permissible. The odor of cod-liver oil makes it objectionable. The oil should be sterilized by heating for several minutes and placed in sterilized bottles; it should be applied with sterilized cotton or a thoroughly disinfected hand.
All authorities agree that massage and passive movements are beneficial. The infant's limbs should be free so that movements are possible. Complete swaddling, therefore, is unwise. It was our custom to massage the infant every morning after the bath. The loose clothing permitted active movement. A good cry several times a day is helpful in that it removes atelectasis and increases oxygenation.
Figure 6. Diagram illustrating the mechanism of the Thermoregulator. a, soft rubber disk; b, hollow disk filled with ether, the expansion of which pushes upward the pin c, which closes the opening in the gas inlet and turns off the gas; d, is a screw, by turning which the disk and its attached pin may be raised or lowered, thus making the regulator more or less sensitive to the heat.
Figure 7. The first clothes of a Premature Infant, consisting of a flannel shirt, flannel band, diaper of cotton and guaze, and cotton and gauze envelope.
Figure 8. The aseptic diaper.