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Aro 1901

LIBRARY

PART I.

ATMOSPHERIC PRESSURE AS A THERAPEUTIC AGENT.

It is a well-known fact that the higher we rise above the level of the sea the more rarefied becomes the atmosphere, and the less the pressure upon the surface of the body. At an altitude of 5500 metres the weight of a litre of air is only half as much as at the sea-level, and conversely there is an increase of pressure and in airdensity as we descend below the level of the sea.

Each condition, that of augmented and that of diminished atmospheric pressure, brings about modifications in the gaseous interchanges in the lungs and tissues, and consequently in the functions of the body. For this reason altitude constitutes a very important factor of climate, one which must always be taken into account when we study climate from a therapeutic standpoint.

Very ingenious apparatus is now manufactured which to some extent obviates the necessity of a change of residence, and enables the patient in some instances to obtain at home the requisite modifications of atmospheric pressure. The application of these artificial means for therapeutic ends constitutes aerotherapy.

The methods employed in aërotherapy create conditions which differ sensibly from those produced by a change of altitude, for we are able at will to provide compressed or rarefied air, while residence on a mountain supplies only the latter. Again, the influence of

climate is continuous; but in the case of aerotherapeutic measures the duration of compression and of rarefaction of the atmosphere can be controlled and limited. Finally, we can permit the aërotherapeutic agents to act upon a single part, as, for example, the respiratory system, or upon the entire surface of the body.

The bath of compressed air is patterned after and was suggested by the diving-bell. According to Aristotle, it was known in his day, although its discovery is generally attributed to Sturmius, who lived in the sixteenth century.

In 1786, Smeaton made use for the first time of the force-pump, with the purpose of supplying a diving-bell with the air necessary for respiration.

The effects of compressed air upon the ear and upon respiration were noted by Hamel in 1820; somewhat later Colladon recorded the cure of a diver, whose breathing had been labored, by means of the diving-bell.

The thought to supply compressed air for therapeutic purposes was first conceived by Tabarie in 1832; but his observations were not published until 1838. Junod, in 1835, described the first aërotherapeutic apparatus. He knew that respiration was facilitated by compressed air, that the vital capacity of the lung was increased, and that inspirations became deeper and less frequent. But in his apparatus compression and expansion were effected suddenly. On this account his method was severely criticised by the Academy of Sciences, largely in consequence of a report made upon the method by Magendie.

In 1840, Tabarie founded the first establishment for aërotherapy at Montpellier. To him and to Pravaz, of Lyons, is due the credit for solving the practical difficulties of the method. They laid stress upon the importance of improving the air and removing the pressure in a gentle and gradual manner, and designed appropriate apparatus to attain such a result.

An excellent study of the physiological effects of this method of treatment has been made by von Vivenot.

Although this method originated in France, it gained its first foothold elsewhere, particularly in Austria, Sweden, Scotland, Italy, Denmark, and Russia. Numerous establishments were founded in these countries. At the present time the method is also popular in France.

The bath of compressed air is administered in pneumatic chambers constructed upon the principles of the diving-bell of Smeaton. In France Tabarie's apparatus, as modified by Fontaine, is the most popular. (Fig. 1.) It represents essentially a bell and a force-pump. The bell consists of a cylinder and two hemispherical end-plates; it has a capacity of 8 cubic meters, and is closed by a door that opens from without inward. A U-shaped tube, one branch of which is within the chamber and one without, and which is half-filled with mercury, indicates the pressure that obtains in the chamber. The chamber is also provided with two other tubes-one for supplying air, the other

for ventilation. The former is connected with the hydraulic compressor of Fontaine, constructed after the one employed in the mines of Chemnitz. The air escapes through the ventilating-tube, which arises from the upper part of the chamber. At a single sitting of two hours an individual consumes 8000 litres of air. The changes

in pressure are effected very gradually by means of stopcocks, and, as a rule, an increase of pressure corresponding to two-fifths atmosphere is not exceeded.

Physiological Effects. In studying the effects of compressed air, we shall confine ourselves solely to the consideration of those produced by the aerotherapeutic apparatus.

As the results of treatment by compressed air make themselves felt especially upon the respiratory organs, it is important to understand how the variations in the vital capacity of the lungs and in the forces of expiration and inspiration are estimated. The vital capacity of the lungs is measured by an apparatus known as the spirometer; that invented by Hutchinson, and first modified by Wintrich and subsequently by Schnepf, is the one most widely employed. Recently the spirometer of Galante has come into extensive use.

Instead of these somewhat delicate instruments, which have the fault that they do no always register correctly, Dupont proposes the