Date of Award
1991
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
The purpose of these studies was to examine ageing effects on the dynamics of pulmonary gas exchange and ventilation during the transition from light to moderate work. In the first study maximal oxygen uptake (VO{dollar}\sb2{dollar}max), ventilation threshold (VeT), the time constant for VO{dollar}\sb2{dollar} ({dollar}\tau\sp\prime{dollar}VO{dollar}\sb2{dollar}), and efficiency were determined from a ramp forcing test in eighty-three males aged 30 to 84y. The results showed a decline in VO{dollar}\sb2{dollar}max with age of {dollar}-{dollar}0.037 1{dollar}\cdot{dollar}min{dollar}\sp{lcub}-1{rcub}{dollar} per year. The VeT also declined with age but at one-third the rate of loss of the VO{dollar}\sb2{dollar}max. The {dollar}\tau\sp\prime{dollar}VO{dollar}\sb2{dollar} increased with age; the older group (60+y) had a significantly greater time constant compared to the younger groups (98s vs 69s).;The second study examined the kinetics of pulmonary gas exchange and ventilation across age using a square wave forcing function. The subjects (n = 44) performed a number of repeats of the square wave test requiring 80% of the VO{dollar}\sb2{dollar} at the VeT. The time constant ({dollar}\tau{dollar}) and the time delay ({dollar}\delta{dollar}) were estimated using a monoexponential fit of the on-transient responses. Significant increases in the time constants for VO{dollar}\sb2{dollar}, VCO{dollar}\sb2{dollar}, and V{dollar}\sb{lcub}\rm E{rcub}{dollar} with age were observed with no change in the {dollar}\tau{dollar}HR with age.;In the third study, eight males (mean age 71.0y) completed 24 weeks of aerobic endurance training on cycle ergometers, and four males served as control subjects. After 24 weeks, the training group showed a significant improvement in VO{dollar}\sb2{dollar}max (19%). The {dollar}\tau{dollar}VO{dollar}\sb2{dollar} decreased from 62.2s to 31.9s with the post-training value similar to that reported for young sedentary subjects. The time constants for VCO{dollar}\sb2{dollar} and V{dollar}\sb{lcub}\rm E{rcub}{dollar} both were reduced, but the {dollar}\tau{dollar}HR did not change. The control group were unchanged after 24 weeks, and the trained group were significantly different from the control group in post-training measures for VO{dollar}\sb2{dollar}max, VeT, {dollar}\tau{dollar}VO{dollar}\sb2{dollar}, {dollar}\tau{dollar}VCO{dollar}\sb2{dollar} and {dollar}\tau{dollar}V{dollar}\sb{lcub}\rm E{rcub}{dollar}.;Thus, in the present studies gas exchange kinetics were found to be slowed with age. With an aerobic training programme of older men however, the dynamic aerobic response to the onset of exercise was faster and similar to normal values for young subjects.
Recommended Citation
Babcock, Mark Anthony, "Age-associated Changes In The Kinetics Of Ventilation And Pulmonary Gas Exchange" (1991). Digitized Theses. 1920.
https://ir.lib.uwo.ca/digitizedtheses/1920