AEROTHERAPEUTICS  , the treatment of disease by atmospheric

air: a term which of late has come to be used somewhat more loosely to include also pneumotherapeutics, or the treatment of disease by artificially prepared atmospheres . The physical and chemical properties of atmospheric air, under ordinary pressure or under modified pressure, may be therapeutically utilized either on the external surface of the body, on the respiratory surface, or on both surfaces together . Also modifications may be induced in the ventilation of the lungs by general gymnastics or respiratory gymnastics . The beneficial effects of air under ordinary pressure are now utilized in the open-air treatment of phthisical patients, and the main indications of benefit resulting therefrom are reduction of the fever, improvement of appetite and the induction of sleep . The air, however, maybe modified in composition or in temperature . Inhalation is the most common and successful method of applying it—when modified in composition—to the human body . The methods in use are as follows: (I) Inhalation of gases, as oxygen and nitrous oxide., The dyspnoea and cyanosis of pneumonia, capillary bronchitis, heart failure, &c., are much relieved by the inhalation of oxygen; and nitrous oxide is largely used as an anaesthetic in minor operations . (2) Certain liquids are used as anaesthetics, which volatilize at low temperatures, as chloroform and ether . (3) Mercury and sulphur, both of which require heat for volatilization, are very largely used . In a mercurial or sulphur bath, the patient, enveloped in a sheet, sits on a chair beneath which a spirit lamp is placed to vaporize the drug, the best results being obtained when the atmosphere is surcharged with steam at the same time . The vapour envelops the patient and is absorbed by the skin . This method is extensively used in the treatment of syphilis, and also for scabies and other parasitic affections of the skin .

(4) Moist inhalations are rather losing repute in the

light of modern investigations, which tend to show that nothing lower than the larger bronchial tubes is affected . Complicated apparatus has been devised for the application, although a wide-mouthed jug filled with boiling water, into which the drug is thrown, is almost equally efficacious . Artificial atmospheres may be made for invalids by respirators which cover the mouth and nose, the air being drawn through tow or sponge, on which is sprinkled the disinfectant to be used . This is most valuable in the intensely offensive breath of some cases of bronchiectasis . The air may be modified as to temperature . Cold air at 32-330 F. has been used in chronic catarrhal conditions of the lungs, with the result that cough diminishes, the pulse becomes fuller and slower and the general condition improves . The more recent observations of Pasquale di Tullio go far to show that this may be immensely valuable in the treatment of haemoptysis . The inspiration of superheated dry air has been the subject of much investigation, but with very doubtful results . Hot air applied to the skin is more noteworthy in its therapeutic effects . If a current of hot air is directed upon healthy skin, the latter becomes pale and contracts in consequence of vasoconstriction . But if it is directed on a patch of diseased skin, as in lupus, an inflammatory reaction is set up and the diseased part begins to undergo necrosis . This fact has been used with good results in hipus, otorrhoea, rhinitis and other nasal and laryngeal troubles .

Lastly the air may be either compressed or rarefied . The physiological effects of compressed air were first studied in diving-bells, and more recently in caissons .

Caisson workers at first enjoy increased strength, vigour and appetite; later, how-ever, the opposite effect is produced and intense debility supervenes . In addition, caisson workers suffer from a series of troubles which are known as accidents of decompression . (See CAISSON DISEASE.) But, therapeutically, compressed air has been utilized by means of pneumatic chambers large enough to hold one or more adults at the time, in which the pressure of the atmosphere can be exactly regulated . This form of treatment has been found of much value in the treatment of emphysema, early pulmonary tuberculosis (not in the presence of persistent high temperature, haemorrhage, softening or suppuration), delayed absorption of pleural effusions, heart disease, anaemia and chlorosis . But compressed air is contra-indicated in advanced tubercle, fever, and in diseases of kidneys, liver or intestines . Rarefied air was used as long ago as 1835, by V . T . Junod, who utilized it for local application by inventing the Junod Boot . By means of this the blood could be drawn into any part to which it was applied, the vessels of which became gorged with blood at the expense of internal organs . More recently this method of treatment has undergone far-reaching developments and is known as the passive hyperaemic treatment .

There are also various forms of apparatus by means of which air at greater or lesser pressures may be drawn into the lungs, and for the performance of

lung gymnastics of various kinds . Mr Ketchum of the United States has invented one which is much used . A committee of the Brompton Hospital, London, investigating its capabilities, decided that its use brought about (1) an increase of chest circumference, and (2) in cases of consolidation of the lung a diminution in the area of dulness .