On the Inhalation of the Vapour of Ether by John Snow

I have spoken of a knowledge of the strength of the vapour as being essential to a correct determination of the state of the patient at all times: and this brings us to the apparatus for the administration of the vapour, as, without a suitable one, the proportions of air and of vapour cannot be determined.

I had the honour of showing that these proportions could be easily and precisely controlled by means of the temperature [a] and of introducing an inhaler, by which the quantity of vapour in the air the patient breathes can be accurately regulated. It is made of metal, the best conductor of caloric, and placed in contact with water, the best and most convenient regulator of temperature; and, consequently, we are enabled to avail ourselves of the law which determines the quantity of vapour of ether that air will take up, and hold in suspension at various temperatures; in order to regulate the strength of the vaporized air as we ,wish.

The opportunity was afforded me of using the apparatus soon after it was made, very frequently, in St. George's Hospital, and I believe that this was the first institution in which the vapour of ether was constantly applied with uniform and complete success in surgical operations. Several alterations in the details of the instrument were made, after it was delineated in the medical journals in the early part of the year, but the following drawings show the form in which I have used it for the last three months.(See engraving [figure 1], of which the following is the description.)

A. Box of japanned tin or plated copper, of the size and form of a thick octavo volume, serving as a water-bath when the apparatus is in use, and at other times containing the elastic tube and face-pieces. Attached to this by clasps, and moveable at pleasure, is

B. The spiral ether chamber, of thin tinned brass, or copper plated with silver.

The tube screwed into the opening at which the air enters is merely for preventing a trifling loss of ether which would arise from evaporation of it into the apartment during the process; and it effects this object in a more simple manner than a valve would, and offers less resistance to the ingress of air than the most delicately-balanced valve. The vapour of ether, being heavier than air, will not diffuse itself, in opposition to gravity, through the air in the tube, in the short space of time between the inspirations of the patient. When an inspiration is taken, the air, having entered by this tube, which is five- eighths of an inch in internal diameter, passes round four times on the surface of the ether, and becomes saturated with its vapour, and expanded by it, in the same way that air gets saturated and expanded with the vapour of water in passing over the surface of the sea. This spiral arrangement is adopted from the inhaler of Mr. Julius Jeffreys for aqueous vapour. The dimensions of the ether chamber (see engraving [Figure 2]) are not a matter of indifference. It is nearly six inches in diameter, and an inch and a quarter in depth. The depth of the first I used was two inches; afterwards it was one inch, and finally the present depth was determined on. It is desirable to have the chamber as shallow as practicable, in order that all the air passing through it may be brought successively in contact with the surface of the ether; and, on the other hand, it is necessary to leave a considerable space above the ether for the air; otherwise, when a patient draws vigorous and deep inspirations, as sometimes happens when he is partly under the influence of ether, the ether will be agitated into waves, and splashed into the elastic tube. The space between the coils of the volute is five-eighths of an inch, and it is of importance to be careful that it is uniformly turned, and presents no inequalities, or the same result -- the splashing of the ether -- may take place. When made with regularity, these proportions of the inhaler leave ample room for the passage of air, as the ether covers the bottom to but a very small depth, even if three or four ounces are put in. This part of the apparatus was at first made of tinned iron, but it was found occasionally to become rusty by use.

The receptacle for water holds above 100 cubic inches. A small quantity of water would be cooled by the conversion of ether into vapour during the process of inhalation, and the intention of accurately regulating the proportion of vapour to the air would not be efficiently fulfilled: 100 cubic inches of water will, however, supply the caloric necessary to the conversion of one or two ounces of ether into vapour, without being much reduced in temperature; and, as the heat of the water employed differs but little from that of the air of the patient's room, it is not much altered during an operation, by radiation or other causes. In order to leave as much room as possible for the operator and his assistants, it is requisite to have an elastic tube of about three feet in length. It ought to be so capacious as to offer no impediment to the most rapid inspiration; and to meet this requirement it must be wider than the trachea, to compensate for the resistance arising from friction of the air against the interior of the tube. It is, therefore, three-quarters of an inch in internal diameter. The pipe for the admission of air to the ether is but five-eighths of an inch in diameter, as stated above; but that is amply sufficient, since it has to give passage to a much smaller volume of fluid than the elastic tube; for the air expands to nearly twice its bulk, in passing over the ether, by the vapour it takes up.

The method of obliging a person to get all the air he breathes through tubes and valves, which is essential to success in the inhalation of ether, is perfectly new, and, in such a process, greater facilities for respiration are required than would generally have been supposed. On this account, many of the apparatuses at first invented did not allow of easy respiration, but offered obstructions to it, by sponges, by the ether itself, by valves of insufficient size, but more particularly by tubes of too narrow calibre; and there is reason to believe that, in many instances, this was the cause of failure, and that in others the insensibility, when produced, was partly due to asphyxia -- a circumstance especially to be avoided: for, as I stated at the Westminster Medical Society on Feb. 13, [b] I found that when an animal was gradually asphyxiated by mixing carbonic gas with the air, or, what amounts to nearly the same thing, by compelling it to breathe in a limited quantity of air, insensibility to injuries was induced; but, that it was a painful process to induce insensibility in this way, and also dangerous to the life of the animal-the insensibility so induced being of short duration before it ended either in death, or recovery to a state of sensibility; circumstances which practically cause it to differ widely from the state of etherization.

For the first three months I used a mouth-piece which did not include the nostrils; consequently they had to be closed, and the patient was obliged to breathe entirely by the mouth. This plan always succeeded (except, perhaps, in one instance), and generally very well, but sometimes not without difficulty; for some of the adult patients, after they lost their consciousness, made such strong instinctive efforts to breathe by the nostrils, that the air was forced through the lachrymal ducts, and occasionally they held the breath altogether for a short time, and were getting purple in the face, when the nostrils had to be liberated, for a short time, to allow respiration of the external air, and thus a delay was occasioned. I was therefore ready to adopt a face-piece invented by Mr. Sibson, of the General Hospital, Nottingham, which permitted inhalation by the nostrils as well as by the mouth. This face-piece I used for some time, and it was the foundation of that I now use, which has been altered, however, considerably from it in form, to allow of the introduction of valves into it, and a greater adaptation to faces of different dimensions.

In the face-piece depicted (figure 3), the central part, containing the valves, is made of metal-brass, tinned iron, or plated copper; all the rest of thin sheet-lead, the pliability of which admits of its being easily adapted to the peculiar form of the features. The lead is covered with silk or glove-leather externally, and is lined with oil-silk where it comes in contact with the face. The valves are made of vulcanised India rubber; they are light, are attached so as to rise with the least appreciable force, and they close again, of themselves, in any posture in which the patient can be required to be placed. I have contrived the expiratory valve to turn on a pivot, so as to allow of the admission of external air, and to supersede the use of a ferrule or two-way tap, at the same time that it is performing the office of a valve. It is advisable, however, to make use of every contrivance of this kind for the admission of additional air to that which has passed over the ether as little as possible, and to regulate the strength of the vapour by the temperature alone; for we can only form a rough estimate of how much air is thus admitted. When a stop-cock with graduated openings is used, it at first sight appears different; but the air passes through the external openings in preference to the more circuitous route over the ether; and when the respiration is gentle, the whole of the air the patient breathes may enter by an outward opening that would only admit a third part of what he inspires when the respiration is forcible.[c]

It is generally known that the ordinary rectified sulphuric ether is unsuited for inhalation, on account of its containing a considerable quantity of alcohol, the vapour of which is irritating to the air-passages. The alcohol also alters the boiling point of the ether, and the elastic force of its vapour at all temperatures, consequently, without having the ether free from it, we should be unable to regulate, by means of the temperature, the proportion of vapour in the air that the patient breathes. The alcohol can be separated by means of water, and what is called washed ether is now supplied, for inhaling, by the principal druggists and surgical instrument makers. Common sulphuric ether can be prepared, for inhalation, by shaking it well up with twice its bulk of water, in a bottle, allowing it to stand for two or three minutes, and then decanting off for use the ether which floats on the top, whilst the alcohol is left mixed with the water. The water takes up a considerable portion of ether, as well as the alcohol, in this operation, which is, consequently, attended with loss when the washings cannot be re-distilled, and turned to account. It is therefore better for the surgeon to procure ether ready prepared.

Ether combines with about one-tenth of its volume of water in being washed: this can be separated by potash or chloride of calcium, and most completely by distilling from quicklime: but I think it preferable, as I stated in a lecture at the United Service Institution,[d] to allow this small quantity of water to remain in the ether, in order that the air which is inhaled with the vapour of ether may be always saturated also with vapour of water, when it will be more bland, and less irritating, than if it contained but little moisture, as is always the condition of air in frosty weather, and often under other circumstances. Some attempts have been made, by means of complicated and expensive apparatus, to add the vapour of water to that of ether, but I believe without succeeding in that indication, unless at the sacrifice of more important ones, whilst this object can be fulfilled by the simple and economical expedient of not separating the water from the washed ether. (3)

The specific gravity of ether of this kind, i.e. free from alcohol, but containing water, is -735 at a temperature of 60° Fahrenheit, and it boils at about 98°.

The following table is the result of a fresh set of experiments, made on the above kind of ether, in the way described in my paper in the Medical Gazette of March 19, and differs a little from the table then published: --

TABLE Of the Quantity of Vapour of Ether that 100 Cubic Inches of Air will take up at different Temperatures.
Temp. Fah.	Cubic inches of vapour.	Minims of ether.
50 ̊	52	64
51 ̊	54	66
52 ̊	56	69
53 ̊	59	72
54 ̊	62	76
55 ̊	65	80
56 ̊	68	84
57 ̊	72	88
58 ̊	76	93
59 ̊	80	98
60 ̊	84	102
61 ̊	88	107
62 ̊	92	112
63 ̊	97	117
64 ̊	102	122
65 ̊	107	128
66 ̊	112	134
67 ̊	117	140
68 ̊	123	147
69 ̊	130	156
70 ̊	138	165

[b] Med. Gaz. Feb. 26, p. 383. M. Flourens, also, Gaz. des Hopitaux, 20 Mars, remarks on the similarity of the phenomena of asphyxia induced in this way, to those of etherization.

[c] Mr. Ferguson, 21, Giltspur Street, City, made the apparatus in the first instance; and Mr. Matthews, Portugal Street, Lincoln's Inn, Messrs. Philp and Whicker, and Mr. Coxeter, have since made it, and there is no restriction respecting the making of it.