Relationship between changes in pulmonary V̇O₂ kinetics and autonomic regulation of blood flow.
Various regulatory mechanisms of pulmonary oxygen uptake (V̇O2) kinetics have been postulated. The purpose of this study was to investigate the relationship between vagal withdrawal, measured using RMSSDRR, the root mean square of successive differences in cardiac interval (RR) kinetics, a mediator of oxygen delivery, and V̇O2 kinetics. Forty-nine healthy adults (23 ± 3 years; 72 ± 13 kg; 1.80 ± 0.08 m) performed multiple repeat transitions to moderate- and heavy-intensity exercise. Electrocardiography, impedance cardiography, and pulmonary gas exchange parameters were measured throughout; time domain measures of heart rate variability were subsequently derived. The parameters describing the dynamic response of V̇O2, cardiac output (Q) and RMSSDRR were determined using a mono-exponential model. During heavy-intensity exercise, the phase II τ of V̇O2 was significantly correlated with the τ of RR (r = 0.36, P < 0.05), Q (r = 0.67, P < 0.05), and RMSSDRR (r = 0.38, P < 0.05). The τ describing the rise in Q explained 47% of the variation in V̇O2 τ, with 30% of the rate of this rise in Q explained by the τ of RR and RMSSDRR. No relationship was evident between V̇O2 kinetics and those of Q, RR, or RMSSDRR during moderate exercise. Vagal withdrawal kinetics support the concept of a centrally mediated oxygen delivery limitation partly regulating V̇O2 kinetics during heavy-, but not moderate-, intensity exercise.
College of Engineering, Swansea University, Wales, UK.
M A
MA
McNarry
College of Engineering, Swansea University, Wales, UK.|Faculty of Health Sciences, La Trobe University, Melbourne, Victoria, Australia.
M I C
MI
Kingsley
College of Engineering, Swansea University, Wales, UK.
M J
MJ
Lewis
D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D002307:Cardiography, Impedance; D003430:Cross-Sectional Studies; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D007700:Kinetics; D008168:Lung / Q000502:physiology*; D008297:Male; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange; D012039:Regional Blood Flow / Q000502:physiology; D013318:Stroke Volume; D013997:Time Factors; D055815:Young Adult
V˙O2 kinetics; cardiac output; heart rate variability; oxygen delivery