Respiratory Compensation, as Evidenced by a Declining Arterial and End-Tidal PCO2,Is Attenuated During Fast Ramp Exercise Functions

  • B. W. Scheuermann
  • J. M. Kowalchuk
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 393)


During low to moderate intensity exercise below the ventilatory threshold (Tvent), ventilation \( ({\dot V_E}) \) increases in proportion to CO2 production (\( \dot V \)CO2), resulting in arterial PCO2(PaCO2) remaining at, or increasing slightly above, resting levels. As the exercise intensity increases beyond the Tvent, \( {\dot V_E} \) increases at a faster rate than \( \dot V \)CO2 (i.e. hyperventilation with respect to \( \dot V \)CO2) when the work rate (WR) is incremented slowly (i.e. a steady-or quasi-steady-state is reached during each step) (7,8). However, when the WR is increased rapidly (i.e. using step increments of min or ramp exercise functions), \( {\dot V_E} \) continues to increase in proportion to \( \dot V \)CO2 as the end-tidal (PETCO2) and arterial PCO2remain relatively constant (i.e. isocapnic buffering) (8,9). This isocapnic buffering phase reflects a specific ventilatory response to exercise above the Tvent where a combination of increased breathing frequency (f) and decreased time of expiration (TE) effectively curtail the systematic increase in PETCO2 and PaCO2 associated with exercise below Tvent(8). In this exercise paradigm respiratory compensation for the developing acidosis is delayed relative to the Tvent and follows the period of isocapnic buffering.


Work Rate Ventilatory Threshold Moderate Intensity Exercise Respiratory Compensation Exercise Intensity Increase 
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Copyright information

© Springer Science+Business Media New York 1995

Authors and Affiliations

  • B. W. Scheuermann
    • 1
  • J. M. Kowalchuk
    • 1
  1. 1.Faculty of Kinesiology and Department of PhysiologyUniversity of Western OntarioLondonCanada

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