Nearly half (47%) of patients with mechanical ventilation in the intensive care unit report having dyspnea. This respiratory distress, with a feeling of "thirst for air", often reaches unbearable limits and is a major factor in the deterioration of the quality of life and the prognosis of patients. Physiopathological mechanisms of dyspnea are beginning better understood and have analogies with those of pain. Like pain, dyspnea often persists despite appropriate treatment of the cause, because of perceptual dysfunction related to changes in cortical excitability and neuronal plasticity and requires specific treatments. Studies have shown that Transcranial Stimulation by low Current (tDCS) was able to modulate the perception of acute pain induced and chronic pain. The tDCS modulates the functioning of a whole set of brain structures including the anterior cingulate gyrus, the prefrontal cortex, the thalamus and the brain stem, some of which have an established role in the central integration of pain and dyspnea. The investigators have recently demonstrated that the application of tDCS on the primary cortical motor area reduces the excitability of the central neurological pathways dedicated to the respiratory muscles in healthy subjects. The investigators therefore hypothesize that tDCS could relieve dyspnea in intensive care. In this research project, the investigators propose to evaluate the efficiency of tDCS on dyspnea in patients admitted to intensive care unit, having sepsis and mechanically ventilated.

Inclusion Criteria:

• Adult patient, hospitalized in intensive care unit, presenting a sepsis, having required a mechanical ventilation since at least 24h.
• Non-sedated or showing good wake up (Richmond Agitation-Sedation Scale score (RASS)> -3 at inclusion (Sessler et al., 2002)) within 48 hours after cessation of sedation
• Patient able to answer by "yes" or "no" to simple questions
• Showing significant dyspnea (level ≥ 4) on the A1 sub-scale of the Multidimensional Dyspnea Profile (MPD-A1 ≥ 4).
• Signature of informed consent by the patient or his relative.

Exclusion Criteria:

• Patient under guardianship,
• Wake up delay, coma (GCS ≤ 8), or severe agitation.
• chronic respiratory pathology
• respiratory pathology, neuromuscular or neuro-sensory disability (auditory or visual).
• Cranioplasty
• Language barrier, refusal to participate in the study or to sign the informed consent,
• Pregnant or nursing woman,
• No affiliation to a social security scheme.