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Dynamics of pulmonary gas exchange and systemic oxygen delivery during exercise transcients in humans

English title Dynamics of pulmonary gas exchange and systemic oxygen delivery during exercise transcients in humans
Applicant Ferretti Guido
Number 114033
Funding scheme Project funding (Div. I-III)
Research institution Dépt des Neurosciences Fondamentales Faculté de Médecine Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Neurophysiology and Brain Research
Start/End 01.10.2006 - 30.09.2009
Approved amount 260'000.00
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All Disciplines (2)

Discipline
Neurophysiology and Brain Research
Cardiovascular Research

Keywords (6)

human physiology; exercise; neural control; cardiovascular system; gas exchange; dynamics

Lay Summary (English)

Lead
Lay summary
The neural control of circulation at the start of an exercise, and its interactions with respiration, are poorly understood. It was recently proposed that the dynamics of lung oxygen uptake and muscle oxygen consumption are dissociated, and may respond to different control mechanisms. The changes in lung oxygen uptake would be dictated by the cardiovascular response to exercise - cardiac output (the amount of blood pumped by the heart in a unit of time) and oxygen flow in arterial blood.The changes in cardiac output at exercise onset have two components: one, very fast, may be due to withdrawal of vagal stimulation (the inhibitory branch of vegetative innervation); the other, delayed and slower, might parallel sympathetic drive stimulation (the excitatory branch of vegetative innervation). However, when the changes in cardiac output and lung oxygen uptake at exercise onset are assessed in supine posture, the rapid component disappears, although vagal activation is greater in supine than in upright posture. This contradicts the notion that vagal withdrawal is a major determinant of the rapid component of the kinetics of cardiac output and lung oxygen uptake, suggesting that also baroreflexes (reflex reduction of heart rate by an increase in blood pressure) may play a role in the dynamic response to exercise. This project is aimed at studying the roles of i) Vagal withdrawal ii) Sympathetic stimulation, and iii) Cardiopulmonary baroreflexes in the cardiopulmonary response at exercise start. These last are related to pressure changes in the pulmonary circulation, and are stimulated in supine posture, but inhibited when a negative pressure is applied to the lower limbs (LBNP). To these aims, we will determine in humans with non-invasive techniques the beat-by-beat changes of cardiac output and the breath-by-breath changes of lung oxygen uptake at the onset of light exercise, upright and supine, in theseconditions: i) Vagal system blockade with atropine, compared with the normal condition; ii) Sympathetic system blockade with metoprolol, compared with the normal condition; iii) Increasing levels of LBNP in supine posture, compared with the normal condition supine. We hope, through a better understanding of the cardiopulmonary regulation during exercise transients, to contribute a brick to the construction of a general theory of the neural regulation of the cardiovascular system, which we still miss. Such a theory would help in understanding the slow kinetics of lung oxygen uptake in several diseases, such as chronic heart failure, type II diabetes, heart and heart-and-lung transplantation, as well as some aspects of the origin of essential hypertension.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

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Associated projects

Number Title Start Funding scheme
127620 Dynamics of pulmonary gas exchange and systemic oxygen delivery during exercise transients in patients affected by specific cardiopulmonary diseases 01.10.2009 Project funding (Div. I-III)
127620 Dynamics of pulmonary gas exchange and systemic oxygen delivery during exercise transients in patients affected by specific cardiopulmonary diseases 01.10.2009 Project funding (Div. I-III)

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