This section is from the book "Dental Medicine. A Manual Of Dental Materia Medica And Therapeutics", by Ferdinand J. S. Gorgas. Also available from Amazon: Dental Medicine.
A method first suggested by the late Dr. W. G. A. Bonwell, and from which he claimed a similar effect to that of ether, chloroform and nitrous-oxide gas in their primary stages, and to render the patient sufficiently unconscious to any acute pain from any operation, where the time consumed is not over from twenty to thirty seconds. "While the special senses are in partial action, the sense of pain is obliterated and, in many cases, completely annulled, consciousness and general sensibility being preserved." "To accomplish this, each patient must be instructed how to act and what to expect. As simple as it may seem, there is a proper and consistent plan to enable you to reach full success. Before the patient commences to inhale he is informed of the fact that while he will be unconscious of pain, he will know full or partially well any touch upon his person; that the inhalation must be vigorously kept up during the whole operation, without for an instant stopping; that the more energetically and steadily he breathes, the more perfect the effect. It is obligatory to do so, on account of its evanescent effects, which demand that the patient be pushed by the operator over energetic appeals to 'go on.' It is very difficult for any one to respire over one hundred times to the minute, as he will become by that time so exhausted as not to be able to breathe at all. For the next minute following the completion of the operation, the subject will not breathe more than once or twice. Very few have force enough left to raise hand or foot. The voluntary muscles have nearly all been subjugated and overcome by the undue effort at forced inhalation of one hundred and seventeen, the normal standard.
" The heart's action is not increased more than from seventy (the average) to eighty and sometimes ninety, but is much enfeebled, or throwing a lesser quantity of blood. The face becomes suffused, as in blowing a fire or in stooping, which continues until the breathing is suspended, when the face becomes paler. (Have not noticed any purple, as from asphyxia by a deprivation of oxygen.) The vision becomes darkened, and a giddiness soon appears. The voluntary muscles farthest from the heart seem first to be affected, and the feet and hands, particularly the latter, have a numbness at their extremities, which increases until, in many cases, there is partial paralysis as far as the elbow, while the limbs become fixed. The hands are so thoroughly affected, that when open the patient is powerless to close them, and vice versa. There is a vacant gaze from the eyes, and a looking into space without blinking of the eyelids for a minute or more. The head seems incapable of being held erect, and there is no movement of the arms or legs, as is usual when in great pain. There is no disposition on the part of the patient to take hold of the operator's hand or interfere with the operation." Dr. Bonwell based his method on the following theory: -
1. Diversion of the will-force in the act of forced respiration at a moment when the heart and lungs have been in normal reciprocal action (twenty respirations to eighty pulsations); which act could not be made and carried up to one hundred respirations per minute without such concentrated effort that ordinary pain could make no impression upon the brain while this abstraction was kept up.
2. There is a specific effect resulting from enforced respiration of one hundred to the minute, due to the excess of carbonic acid gas set free from the tissues, generated by this enforced normal act of throwing into the lungs five times the normal amount of oxygen demanded in one minute, when the heart has not been aroused to exalted action, which comes from violent action in running, or where one is suddenly startled; which excess of carbonic acid cannot escape in the same ratio from the lungs, since the heart does not respond to the proportionate overaction of the lungs.
3. "Hyperaemia is the last in the chain of effects; which is due to the excessive amount of air passing into the lungs, preventing but little more than the normal quantity of blood from passing from the heart into the arterial circulation, but damming it up in the brain, as well as throughout the capillary and venous systems as well as upon the heart, the same as if it were suspended in that gas outside the body."
Dr. A. Hewson agrees with Dr. Bonwell as to the efficacy of rapid breathing as a pain obtunder, yet he differs with him as to the theory or nature of the changes in the different symptoms brought about during its progress. Dr. Hewson states: "Every circumstance would therefore seem to indicate that this process of inducing insensibility to pain is one essentially of diminished oxidization and decarbonization of the blood, and recognizing such a state as belonging to the initiative stage of all anaesthetics, when insensibility to pain is positively marked, we have no necessity for begging any special theory for this process, as in its action it readily comes under the category of such agents, and is thus not either an absurdity or an impossibility from a scientific point of view."