title: Changes in regional emptying sequence need not change maximum expiratory flow.
abstract: Nine normal young men inhaled boluses of He at the onset of slow vital capacity (VC) inspirations. During the subsequent VC expirations, we measured expired flow, volume, and He concentrations. Expirations consisted of full or partial maximum expiratory flow-volume (MEFV) maneuvers. Full maneuvers were forced expirations from total lung capacity (TLC). Partial maneuvers were accomplished by expiring slowly from TLC to 70, 60, 50, and 40% VC and then initiating forced expiration. Expired He concentrations from full and partial maneuvers were compared with each other and with those resulting from slow expirations. At comparable volumes less than 50% VC, flow during partial and full MEFV maneuvers did not differ. Expired He concentrations were higher during partial maneuvers than during full ones; at the onset of partial maneuvers upper zone emptying predominated, whereas this was not the case at the same lung volumes during maneuvers initiated at TLC. We observed substantial differences in regional emptying sequence that did not influence maximum expiratory flow.
mesh_terms: D000328:Adult; D005540:Forced Expiratory Flow Rates; D006371:Helium; D006801:Humans; D008297:Male; D008448:Maximal Expiratory Flow Rate; D008449:Maximal Expiratory Flow-Volume Curves; D012119:Respiration; D014797:Vital Capacity
chemical_list: D006371:Helium