Reduction in bronchodilation following a deep inhalation is poorly relatedto airway inflammation in asthma

In patients with bronchial asthma, forced expiratory flows are differently sensitive to a previous volume history. A reduced ability of a deep inhalat ion (DI) to dilate obstructed airways has been hypothesized to be a physiol ogical marker for the degree of airway responsiveness and to relate to the presence and magnitude of inflammation in the lung, even in mild stable ast hma. However, there are at present doubts as to whether functional changes could be used as a substitute for airway inflammation studies. In order to investigate the interrelations among airway inflammation, bronc hial hyperresponsiveness and effects of volume history, 58 consecutive asth matics with mild to moderate asthma were studied, The effects of DI were as sessed as the isovolumic ratio of flows from forced expiratory manoeuvres s tarted from maximal (M) or partial (P) lung inflation. Airway inflammation was assessed by using induced sputum, Sputum was analysed for total and dif ferential cell counts, and levels of eosinophil cationic protein (ECP) whic h reflects eosinophil activation. Airway responsiveness was assessed as the provocative concentration of histamine which caused a 20% fall in forced e xpiratory volume in one second (FEV1) from control (PC20). The M/P ratio was significantly related to ECP (r=-0.31, p<0.03) and eosino phils (r=-0.29, p<0.03), FEV1/vital capacity (VC) (r=0.32; p<0.01), clinica l score (r=-0.33; p<0.03) and age (r=-0.41; p<0.0001). In a stepwise multip le regression analysis including age, score, baseline lung function, ECP, n umber of eosinophils and the response to beta(2)-agonist, age (p<0.037) pre dicted a small amount of the variance in M/P ratio (r(2)=0.12). It is concluded that volume history response is substantially independent o f both sputum outcomes (inflammatory cell number and eosinophil cationic pr otein) and bronchial hyperresponsiveness; rather it seems to be associated with anthropometric characteristics. Functional aspects do not provide info rmation on eosinophilic, probably central, airway inflammation.