title: The site of airflow limitation in asthma: the effect of time, acute exacerbations of disease and clinical features.
abstract: We have used the helium/oxygen technique to assess the main site of airflow obstruction in patients with asthma. Of 14 out-patients with asthma studied serially (minimum of three observations over 5-12 months) 10 remained either responders or non-responders to helium/oxygen (He/O2) on each occasion tested, despite variations in severity of airflow obstruction. Four out of six patients studied during an acute exacerbation of asthma were initially non-responders to He/O2 but became responders during recovery. The response to He/O2 of these and 15 other patients with asthma was compared with a variety of clinical features. There was a statistically significant decline in flow rate response to He/O2 breathing with increased length of history of asthma, but no differences in smoking history, are, sex or atopic status between the responders and non-responders. This implies a progressive involvement of smaller peripheral airways during the course of the disease. Perhaps more systematic treatment of young asthmatics would prevent this.
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000503:physiopathology*; D005260:Female; D005540:Forced Expiratory Flow Rates; D006371:Helium; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen; D011446:Prospective Studies; D014797:Vital Capacity
chemical_list: D006371:Helium; D010100:Oxygen