Dyspnea is a frequent, mostly unpleasant and long-lasting, but also often undertreated symptom. Transcranial direct current stimulation (tDCS), a new non invasive method to modify brain activation has shown good efficacy in the treatment of pain especially in the clinical context. Given the fact that dyspnea has many common characteristics with pain, especially concerning the brain areas involved in its central processing, we hypothesize that tDCS may also modify the perception of dyspnea. In order to test this, we first shall determine whether tDCS has a significant effect on acutely induced dyspnea in healthy volunteers. In case of promising results of this pilot study, the next step will be the evaluation of the benefit of tDCS in patients with severe dyspnea.

Dyspnea will be induced by breathing through a combination of an external resistive load and a long tube (inducing CO2 rebreathing) (resulting in a sensation of both increased respiratory effort and air hunger). tDCS will be applied during 15 minutes either over the motor/premotor or over the insular cortex (i.e. 2 brain regions that have previously been shown to be involved in dyspnea perception and/or modulation) in 2 parallel groups of healthy subjects. For each study group, the effect of tDCS on dyspnea perception and on respiratory parameters will be compared between 2 active (anodal and cathodal) and a sham tDCS stimulation (placebo).

Inclusion Criteria:

• Registered at the National List of persons taking part in clinical research
• Signed consent form
• Subjects of both genders aged of at least 18 years
• Perfect understanding of the instructions and of sensory scaling
• Prior medical examination

Exclusion Criteria:

• Any current or past disease, in particular respiratory, neurological and psychiatric disorders
• Regular use of drugs, especially those having an impact on respiratory, neurological systems (most specifically those with an effect on the central nervous system)
• Unwilling to participate
• Vulnerable people as defined in the provisions relating to biomedical researches and described in the Code of Public Health.
• Unable to cooperate
• Pregnancy or lactation
• No affiliation to a social security system.