Perception of airway obstruction in asthmatic patients in acute and subacute conditions

To evaluate the influence of temporal adaptation we studied 20 patients wit h PFER measurement twice a day during 4 weeks and a simultaneous recording of a symptom score (SS). A histamine challenge test was performed measuring Borg score at each FEV1 fall during the test. The correlation between FEV1 fall during histamine test and Borg score (Delta FEV1H) was better (media r 0.62 +/- 0.35) than SS vs PEFR (media r morning SS vs morning PEFR 0.24 /- 0.22, media r evening SS vs evening PEFR 0.30 +/- 0.20). All the patient s had at least one episode of PEFR fall > 20% not detected (SS = 0) but onl y 44% showed Delta FEV1H > 20% with Borg score = 0. Forty eight episodes of PEFR fall > 20% were recorded, 67% were not perceived (SS = 0) and 33 epis odes of Delta FEV1H > 20% with only 33% of them not perceived (Borg = 0). W e conclude that patients perceive in a lower degree airway obstruction that takes place in days compared to that developing in minutes.