title: Flow limitation and regulation of functional residual capacity during exercise in a physically active aging population.
abstract: In 29 older (69 +/- 1 yr), physically active subjects (VO2max = 44 +/- 2 ml.kg-1.min-1), we determined the effect of an age-related decline in elastic lung recoil (i.e., Vmax50 = 65% of 30-yr-old adults) on the ventilatory response to progressive exercise. More specifically, we assessed if expiratory airflow limits were achieved and how this may modulate the regulation of end-expiratory lung volume (EELV). We found that with only mild to moderate (50 to 75% VO2max) exercise, the mean EELV was reduced 0.38 +/- 0.07 L, and that expiratory flow limitation was present over 25 +/- 4% of the VT. In 11 subjects during this intensity of exercise, EELV was within their closing capacity. As exercise intensity progressed, VT plateaued at 58 +/- 2% of the vital capacity, and increased expiratory air flow rates were achieved by significantly increasing the EELV back to near resting levels, thereby moving a portion of the expiratory tidal flow-volume envelope away from the constraints of the effort independent portion of the maximal flow-volume curve. During heavy exercise, end-inspiratory lung volume (EILV) approached 90% of TLC. To achieve greater expiratory flow with maximal exercise, EELV remained similar to the previous intensity, and a significantly greater portion of the tidal expiratory flow-volume envelope (greater than 40% of the VT) became flow-limited. Despite this significant expiratory limitation, a rise in EELV, and an EILV approaching TLC, TI/Ttot remained constant throughout exercise, and the ventilatory response for the metabolic demand (VA/VCO2) was appropriate.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, University of Wisconsin School of Medicine, Madison.
authors.forename: B D
authors.initials: BD
authors.lastname: Johnson
authors.forename: W G
authors.initials: WG
authors.lastname: Reddan
authors.forename: D F
authors.initials: DF
authors.lastname: Pegelow
authors.forename: K C
authors.initials: KC
authors.lastname: Seow
authors.forename: J A
authors.initials: JA
authors.lastname: Dempsey
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005652:Functional Residual Capacity / Q000502:physiology*; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D012123:Pulmonary Ventilation / Q000502:physiology*; D012420:Running; D016138:Walking