This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
b. Dry Air. Another method of sustaining the warmth of the body is to surround it with dry air, which is a very bad conductor. But dry air favours greatly the evaporation of liquids, and thus tends to act injuriously, in many instances, on the mucous membrane of the air-passages, and on the skin. It is, therefore, only under peculiar circumstances that it can be resorted to remedially. It is indicated in patients of a debilitated habit, with a disposition to excessive moisture of the surface, and excessive bronchial secretion from chronic disease of the air-passages. In certain cases of pituitous catarrh, or humoral asthma as it was formerly called, with a cool perspiratory state of the surface, confinement to such air may prove useful. This is readily accomplished, in winter, by warming the external cold dry air by passing it over heated surfaces, without supplying water to moisten it, in its passage into the chamber. Great facility for this purpose is afforded by the present plan of heating houses from furnaces in the cellar.
The methods of accomplishing this object are numerous, and each requires a special notice. They may all be included in two divisions; the first embracing those in which the heating body used is dry, the second those in which it is moist. There is an important difference between these two methods. By the first we obtain the effects of heat alone; in the second, the sedative influence of moisture, and the conducting power of water, modify these effects often very materially. These influences will be considered when we come to the methods of applying moist heat.
a. Dry Heat. This is imparted either by radiation, or by the direct contact of the heated medium.
Insolation, or exposure to the rays of the sun, is the most effective mode of obtaining the influence of radiant heat. It is sometimes agreeably stimulant to the old, feeble, and paralytic, and appears to act as a restorative in the debility of convalescence. As the combination of heat and light, in the direct rays of the sun, is essential to the perfect development of vegetables, so is it probably also to that of animals; and there is little doubt that this is one of the influences which, combined together in a journey through the country in the warmer seasons, tend so powerfully to build up a system dilapidated by disease, worn out by over-exertion, or languishing from the confinement, impure air, and indoor dwelling of a town life. To the scrofulous and consumptive, exercise in the pure sunny air is peculiarly beneficial; and the direct warmth of the sun, by a positive stimulation and invigoration of all the vital processes, contributes considerably, I have little doubt, to the favourable influence of a residence in warm climates over a tuberculous diathesis. An excess of it may, of course, be injurious, and must be guarded against, especially its immediate action on the brain.
The radiant heat of a fire may be used as a substitute for insolation in the old and feeble, during winter. The same mode of beating is often used for equalizing the temperature in cases of cold hands and feet; and. in attacks of spasmodic colic, or of subacute and neuralgic rheumutism from exposure to cold, a thorough heating of the feet, before a good fire, will sometimes produce a cure.*
Substances used to impart dry heat to the body by conduction are solid or aeriform.
Of the former class are bottles filled with hot water or heated sand; tin vessels made to fit certain parts of the body, and filled in the same manner; metallic bodies, such as flat-irons heated; hot bricks; bags filled with heated oats, sand, or ashes, and shaped so as to lie conveniently along various parts of the body; and towels heated as hot as the skin will bear them, and applied folded to the surface. These means may be had recourse to in the cold stage of febrile diseases; the advanced stage of the same diseases, with general feebleness and coldness of the extremities; the collapse of cholera and other bowel affections; asphyxia, complete or partial; the external paleness and chilliness attendant on severe colic, and violent spasms of the stomach, gall-duct, and ureters; in short, whenever there is an indication for the general stimulation of heat, or its derivative influence from irritated, congested, or inflamed organs. In cases of great emergency, when some powerful impression may be necessary to rouse the failing sensibilities of the system, a red-hot coal may be applied to the surface, especially to the epigastrium. I have known of an instance of this kind in malignant typhus, in which the patient, who had sunk below the reach of all ordinary stimulants, was roused by this means, and, on recovering afterwards, said that the sensation of the burning coal had been positively agreeable to him, in the state of horrible vacancy of feeling to which he had been reduced. When the solid bodies above enumerated are brought into contact with the surface, care must be taken that they are not hot enough to burn the skin ; and this caution is the more necessary, because the patient is often himself too insensible at the time to give notice of the danger. It is sometimes advisable to wrap them in flannel, in order to interpose a slow conductor between them and the skin.
* A very interesting case of resuscitation, in a new-born infant, under the influence of heat, is recorded by Dr Jos. G. Richardson, of Cayuga Co., New York, in the American Journal of Medical Sciences (January, 1867, p. 128). Induced by the success of Dr. Richardson, of London, in restoring the action of the heart by injecting heated blood into the coronary arteries, he conceived the idea of imitating the experiment on the living body; and, in the case of the infant referred to, finding all other methods, including artificial respiration, but partially successful, he caused the lower extremities of the child to be heated before a fire as highly as could be borne without producing local mischief, and then by pressing the heated blood in the veins of the limbs towards the heart, he endeavoured to introduce it in that state into the coronary vessels. The effect, he states, was "almost miraculous." The heart, which had before acted feebly and involuntarily, quickly began to pulsate energetically, the respiration became continuous, and the prospect of a thorough restoration was very encouraging; but subsequently, in the absence of the physician, death occurred from the officiousness of the nurse in giving nourishment, contrary to the injunction of the physician to avoid it. (Note to the third edition).