Affordable Access

Publisher Website

Mechanism of augmented exercise hyperpnea in chronic heart failure and dead space loading

Authors
Journal
Respiratory Physiology & Neurobiology
1569-9048
Publisher
Elsevier
Publication Date
Volume
186
Issue
1
Identifiers
DOI: 10.1016/j.resp.2012.12.004
Keywords
  • Chronic Heart Failure
  • Physiological Dead Space
  • Dead Space Loading
  • Alveolar Dead Space
  • Anatomical Dead Space
  • Series Dead Space
  • Parallel Dead Space
  • Whipp'S Law
  • Comroe'S Law
  • Fenn–Craig Diagram
  • Exercise Hyperpnea
  • Metabolic Co2 Load
  • Airway Co2 Load
  • Co2 Breathing
  • Arterial [Formula Omitted] Oscillations
  • Cognition
  • Perception
Disciplines
  • Biology
  • Medicine

Abstract

Abstract Patients with chronic heart failure (CHF) suffer increased alveolar VD/VT (dead-space-to-tidal-volume ratio), yet they demonstrate augmented pulmonary ventilation such that arterial PCO2 (PaCO2) remains remarkably normal from rest to moderate exercise. This paradoxical effect suggests that the control law governing exercise hyperpnea is not merely determined by metabolic CO2 production (V˙CO2) per se but is responsive to an apparent (real-feel) metabolic CO2 load (V˙CO2o) that also incorporates the adverse effect of physiological VD/VT on pulmonary CO2 elimination. By contrast, healthy individuals subjected to dead space loading also experience augmented ventilation at rest and during exercise as with increased alveolar VD/VT in CHF, but the resultant response is hypercapnic instead of eucapnic, as with CO2 breathing. The ventilatory effects of dead space loading are therefore similar to those of increased alveolar VD/VT and CO2 breathing combined. These observations are consistent with the hypothesis that the increased series VD/VT in dead space loading adds to V˙CO2o as with increased alveolar VD/VT in CHF, but this is through rebreathing of CO2 in dead space gas thus creating a virtual (illusory) airway CO2 load within each inspiration, as opposed to a true airway CO2 load during CO2 breathing that clogs the mechanism for CO2 elimination through pulmonary ventilation. Thus, the chemosensing mechanism at the respiratory controller may be responsive to putative drive signals mediated by within-breath PaCO2 oscillations independent of breath-to-breath fluctuations of the mean PaCO2 level. Skeletal muscle afferents feedback, while important for early-phase exercise cardioventilatory dynamics, appears inconsequential for late-phase exercise hyperpnea.

There are no comments yet on this publication. Be the first to share your thoughts.

Statistics

Seen <100 times
0 Comments

More articles like this

Commentary on "Mechanism of augmented exercise hyp...

on Respiratory Physiology & Neuro... Oct 01, 2013

Differential contribution of dead space ventilatio...

on The American Journal of Cardio... Feb 01, 2004

Differential contribution of dead space ventilatio...

on The American Journal of Cardio... Jan 01, 2004
More articles like this..