title: Predominant site of airway resistance in chronic obstructive pulmonary disease.
abstract: The purpose of the present clinical research was to establish the major site of resistance and obstruction in patients with severe, symptomatic chronic obstructive pulmonary disease. We used a noninvasive technique by measuring airflow in a plethysmograph after patients breathed air and after breathing a mixture of 80 percent helium and 20 percent oxygen. In group 1 were 14 patients (mean age, 63 +/- 7 years [+/- 1 SD]) with bronchitis. The ratio of their forced expiratory volume in one second over the vital capacity (FEV1/VC) was 43 +/- 10 percent (mean +/- 1 SD), and their single-breath carbon monoxide diffusing capacity (Dsb) was normal (125 +/- 41 percent of the predicted value). In group 2 were 13 patients with emphysema (mean age, 60 +/- 10 years), whose FEV1/VC was 33 +/- 11 percent and Dsb was 55 +/- 14 percent of predicted. All patients had abnormally low increases in the maximum expiratory flow at midvital capacity after breathing the helium-oxygen mixture. The range in group 1 was -11 percent to +14 percent and in group 2 was -10 percent to +15 percent. Normal subjects in our laboratory show increases of at least +24 percent. This indicates that the limitation of airflow occurs primarily in the small (less than 2 mm in internal diameter) and not the large airways.
mesh_terms: D000368:Aged; D000403:Airway Resistance; D001991:Bronchitis / Q000473:pathology; D004548:Elasticity; D004646:Emphysema / Q000473:pathology; D005260:Female; D006371:Helium; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008448:Maximal Expiratory Flow Rate; D008875:Middle Aged; D010100:Oxygen; D012907:Smoking; D014797:Vital Capacity
chemical_list: D006371:Helium; D010100:Oxygen