title: The maximum expiratory flow-volume curve with air and a low-density gas misture. An analysis of subject and observer variability.
abstract: The subject and intra- and inter-observer variability of three measurements derived from the maximal expiratory flow-volume (MEFV) curve with air and helium-oxygen (HeO2) mixture was determined in ten normal subjects who produced curves in the morning and afternoon of three consecutive days and again on one day a month later. The measurements examined were the maximum flow at 50% vital capacity (V50), the percentage increases in V50 when breathing the He-O2 mixture (delta V50), and the volume at which the curves on air and He-O2 first meet or intersect (VisoV). The delta V50 and VisoV were shown to have a greater degree of variability than the V50 and, in the case of VisoV, this was contributed to significantly by the observer variability. The within-subject variability of the delta V50 and VisoV was so great that the usefulness of these tests in following changes in lung function of individual patients must be questioned.
mesh_terms: D000328:Adult; D005260:Female; D005540:Forced Expiratory Flow Rates; D006371:Helium; D006801:Humans; D007206:Individuality; D008297:Male; D008449:Maximal Expiratory Flow-Volume Curves; D010100:Oxygen; D013997:Time Factors; D014797:Vital Capacity
chemical_list: D006371:Helium; D010100:Oxygen