Relationship between supramaximal flows and flow-limiting mechanisms.
The aim of this study was to evaluate the relationship between supramaximal flows (SF) and indices of airway mechanics. We studied 26 asymptomatic young subjects (13 smokers, mean +/- SD 15.9 +/- 6.6 pack-years. Subjects performed maximal expiratory flow-volume (MEFV) curves, according to the American Thoracic Society (ATS) criteria, on a rolling-seal spirometer and then repeated them through a specially devised valve, which occluded the mouthpiece either 3 or 6 times.s-1 with a ratio of open:closed time of 3:1. Envelope MEFV curves for 3 and 6 Hz occlusions were constructed passing through the SF obtained after each occlusion, and the increment in flow at 50% of vital capacity was measured with respect to the basal curve (delta V' max50). We found that the delta V' max50 at 3 and 6 Hz correlated to the baseline forced mid-expiratory flow (FEF25-75) in % of predicted value (r = -0.73 and r = -0.55, respectively). our results suggest that inhomogeneities within the lung are an important mechanism in the occurrence of supramaximal flow in normal subjects.
Sala
H
H
Hospital Nacional Alejandro Posadas, Haedo, Argentina.
Galindez
F
F
Badolati
A
A
Rodenstein
D
D
D000328:Adult; D000886:Anthropometry; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008168:Lung / Q000502:physiology*; D008297:Male; D010366:Peak Expiratory Flow Rate / Q000502:physiology*; D012016:Reference Values; D012129:Respiratory Function Tests; D012907:Smoking; D013147:Spirometry / Q000379:methods