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)

Abstract

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.

Keywords

Fatigue Dioxide Lithium Lactate Heparin 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Reference

  1. 1.
    Allen, C.J. and N.L. Jones. Rate of change of alveolar carbon dioxide and the control of ventilation during exercise. J. Physiol. (Lond) 355: 1–9, 1984.Google Scholar
  2. 2.
    Beaver, W.L., N. Lamarra and K. Wasserman. Breath-by-breath measurement of true alveolar gas exchange. J. Appl. Physiol.:Respirat. Environ. Exercise Physiol. 51: 1662–1675, 1981.Google Scholar
  3. 3.
    Beaver, W.L., K. Wasserman and B.J. Whipp. A new method for detecting anaerobic threshold by gas exchange. J. Appl. Physiol. 60: 2020–2027, 1986.PubMedGoogle Scholar
  4. 4.
    Edwards, A.D.. S.J. Jennings, C.G. Newstead and C.B. Wolff. The effect of increased lung volume on the expiratory rate of rise of alveolar carbon dioxide tension in normal man.J. Physiol. (Lond) 344: 81–88, 1983.Google Scholar
  5. 5.
    Hughson, R.L. and H.J. Green. Blood acid-base and lactate relationships studied by ramp work tests. Med. Sci. Sports Exerc. 14: 297–302, 1982.PubMedCrossRefGoogle Scholar
  6. 6.
    Ward, S.A. and B.J. Whipp. Influence of body CO2 stores on ventilatory-metabolic coupling during exercise. In: Control of Breathing and its Modelling Perspective, edited by Y. Honda, Y. Miyamoto, K. Konno and J.G. Widdicombe. New York: Plenum Press, 1992, p. 425–431.Google Scholar
  7. 7.
    Wasserman, K., A.L. Van Kessel and G.G. Burton. Interaction of physiological mechanisms during exercise. J. Appl. Physiol. 22: 71–85, 1967.PubMedGoogle Scholar
  8. 8.
    Whipp, B.J., J.A. Davis and K. Wasserman. Ventilatory control of the ‘isocapnic buffering’ region in rapidly-incremental exercise. Respir. Physiol. 76: 357–368, 1989.PubMedCrossRefGoogle Scholar
  9. Whipp, B.J. and S.A. Ward. Coupling of ventilation to pulmonary gas exchange during exercise. In: Exercise: Pulmonary Physiology an1d Pathophysiology, edited by B.J. Whipp and K. Wasserman. New York: Marcel Dekker, Inc., 1991, P. 271–307.Google Scholar

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

Personalised recommendations