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Exercise hyperventilation in chronic heart failure is not caused by systemic lactic acidosis
Roland Wensel1, Darrel P Francis, Panagiota Georgiadou
1National Heart and Lung Institute, Imperial College of Science, Technology and Medicine, London, UK. roland.wensel@klinik.uni-regensburg.de
European Journal of Heart Failure
|December 6, 2005
Summary
In heart failure patients, elevated exercise ventilation and low carbon dioxide levels are not caused by lactic acidosis. This study refutes lactic acidosis as a trigger for hyperventilation during exercise in heart failure.
Area of Science:
- Cardiopulmonary exercise testing
- Heart failure pathophysiology
- Respiratory physiology
Background:
- Patients with heart failure exhibit an exaggerated ventilatory response during exercise.
- This response is linked to impaired gas exchange and reduced arterial partial pressure of carbon dioxide (pCO2).
Purpose of the Study:
- To investigate if lactic acidosis stimulates the increased ventilation observed during exercise in heart failure.
- To determine if lactic acidosis abnormally depresses arterial pCO2 in these patients.
Main Methods:
- Studied 18 patients with chronic heart failure.
- Measured ventilatory equivalent for carbon dioxide (VE/VCO2) slope, arterial blood gases, and lactate concentrations during cardiopulmonary exercise testing.
- Analyzed data at rest, peak exercise, and one minute post-exercise.
Main Results:
- No correlation was found between VE/VCO2 slope or peak exercise pCO2 and arterial lactate levels.
- During early recovery, a high VE/VCO2 slope correlated with increased arterial lactate and hydrogen ion concentrations.
- Despite increased lactate and hydrogen ions, arterial pCO2 rose, not fell, during early recovery, correlating with hydrogen ion concentration.
Conclusions:
- The ventilatory response (VE/VCO2 slope) and low arterial pCO2 during exercise in heart failure are unrelated to systemic lactic acidosis.
- Lactic acidosis is not a plausible mechanism driving exercise-induced hyperventilation in heart failure.
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