Reduction in the Vital Capacity of Asthmatic Subjects Following Exposure to Aerosolized Pollen Extracts

Abstract

Changes in vital capacity follow inhalation of extracts of birch, oak, grass, and ragweed pollens and certain other substs. in 6 or 7 asthmatic subjects studied. Exposure was obtained by 15 or less inhalations of aerosolized extract from a hand nebulizer attached to a tube with oxygen flowing at the rate of 6 l./min. Aerosols of the extracting fluid used in preparing the allergenic extracts produced no changes in vital capacity. Reductions down to 60% of the control values were produced by the pollen extracts, and in no case was there any reaction other than cough, a tight feeling in the chest, and symptoms of hay fever. Physical signs of asthma appeared with the more marked reductions in vital capacity but were never striking. Where a reduction in vital capacity followed inhalation of an aerosolized extract, the maximum decrease occurred between 6 and 10 min. after exposure. The vital capacity tended to return to the control value within 50 mins. The test has certain disadvantages. Sufficient data to determine its value in diagnosis are not yet available. Substs. suspected of being clinically important have not always produced a fall in vital capacity. The method is time consuming, and is hampered by the lack of an accurate way to measure the intensity of the exposure to the aerosol. The method, however, is promising in that: (1) Reductions in vital capacity can be safely induced in asthmatic subjects by substs. which can produce asthmatic attacks; (2) the lung, the chief site of the disease, serves as the test organ; (3) the effect of drugs in altering changes in vital capacity following exposure to aerosolized extracts can be readily studied; and (4) the method affords an objective test in many cases since a decrease in vital capacity may occur without the subject being aware of any reaction.