STUDIES ON BRONCHIAL HYPERSENSITIVITY IN CHILDREN FMOM 3 TO 15 YEARS OF AGE WITH SPECIAL REFERENCE TO RESPIRATORY THRESHOLD TO METHACHOLINE IN ASTHM ATICS, LATENT ASTHMATICS AND CHILDREN HAVING PROLONGED COUGH

An Astograph with the combined use of the P-V lissajou method which was newly deviced was useful for measuring respiratory threshold of methacholine in children from 3 to 15 years of age.An yearly change of threshold of methacholine in asthmatics was minimal in spite of the clinical improvement, suggesting that the significance of the improved threshold is great even though it is small.The threshold to methacholine in latent asthmatics was higher than that of asthmatics. There was, however, no difference of distribution of threshold between the group of older than 6 years and that of younger than 6 years of age. In latent asthmatics from the ages 3 to 13 years, 15.6per cent of the cases showed increased bronchial sensitivity during a 3 year observation period. It was also found that in latent asthmatics, bronchial hypersensitivity was independent from family history of atopy and from atopic markers such as serum total IgE, house dust RAST, eosinophiles of blood and of nasal secretions. Lastly, the same tendency as described above was observed in children suffering from a prolonged cough.