Dependence of maximal flow-volume curves on time course of preceding inspiration.
Thirteen normal subjects, sitting in a body plethysmograph and breathing through a pneumotachograph, performed forced vital capacity maneuvers after a rapid inspiration without or with an end-inspiratory pause (maneuvers 1 and 2) and after a slow inspiration without or with an end-inspiratory pause (maneuvers 3 and 4), the pause lasting 4-6 s. Inspirations were initiated close to functional residual capacity. At all lung volumes, expiratory flow was larger with maneuver 1 than with any other maneuver and, over the upper volume range, larger with maneuver 3 than with maneuver 4, whereas it was similar for maneuvers 2 and 4. Relative to corresponding values with maneuver 4, peak expiratory flow was approximately 16 and approximately 4% larger with maneuvers 1 and 3, respectively, whereas forced expiratory volume in 1 s increased by approximately 5% only with maneuver 1. The time dependence of maximal flow-volume curves is consistent with the presence of viscoelastic elements within the respiratory system (D'Angelo et al. J. Appl. Physiol. 70: 2602-2610, 1991).
D'Angelo
E
E
Istituto di Fisiologia Umana I, Università di Milano, Italy.
Prandi
E
E
Milic-Emili
J
J
D000328:Adult; D004576:Electromyography; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008449:Maximal Expiratory Flow-Volume Curves; D012119:Respiration; D012132:Respiratory Muscles / Q000502:physiology; D013997:Time Factors; D014797:Vital Capacity