Effect of age on changes in flow rates and airway conductance after a deep breath.
The effects of aging on changes in maximal expiratory flow rates and specific airway conductance after a deep breath were evaluated in 64 normal subjects. Flow rates (Vp) on partial expiratory flow-volume curves (PEFV), initiated from 60-70% of the vital capacity (VC), were compared with those (Vc) on maximal flow-volume curves (MEFV), initiated from total lung capacity (TLC), at a lung volume corresponding to 25% of VC on the MEFV curves. Specific airway conductance was measured before (sGaw) and after a deep inspiration (sGawDI). Bronchodilation after inspiration to TLC was inferred by Vp/Vc less than 1 and sGaw/sGawDI less than 1. The mean Vp was less than Vc. However, the ratio Vp/Vc increased significantly with age (r = 0.75, P less than 0.001). Specific conductance also increased after a deep inspiration (sGaw less than sGawDI). The ratio sGaw/sGawDIj increased slightly but significantly with age (r = 0.28, P less than 0.02). Measurement of lung elastic recoil pressures before and after a deep breath in a subgroup of patients (n = 14) suggested that the age-related increase in Vp/Vc was secondary to a decrement in the ability of a deep breath to decrease the upstream airway resistance. These findings suggest that even though changes in airway size after a deep breath as measured by sGaw/sGawDI have minimal age dependence, aging diminishes expiratory flow rates of MEFV curves relative to PEFV curves because of a decrease in the ability of a deep breath to increase the size of the peripheral airways.
Berry
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RB
Department of Medicine, Veterans Administration Medical Center, Long Beach 90822.
Pai
U P
UP
Fairshter
R D
RD
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D000403:Airway Resistance / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008448:Maximal Expiratory Flow Rate / Q000502:physiology; D008449:Maximal Expiratory Flow-Volume Curves / Q000502:physiology; D008875:Middle Aged; D012123:Pulmonary Ventilation / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D014109:Total Lung Capacity / Q000502:physiology; D014797:Vital Capacity / Q000502:physiology