Patient with PTSD who has failed to respond to at least one therapeutic approach, psychotherapy or treatment with an SSRI
Nature of the traumatic event: interpersonal violence, including sexual, physical and psychological abuse
PTSD as defined by the DSM-5, with symptoms present for more than 6 months
CAPS-5 score ≥35
Participant who can receive MEOPA or medical oxygen through a face mask
French-speaking
Social security affiliation
Signed consent
A suitable method of contraception for women of childbearing age
You may not be if
Current substance use disorders or history of substance use disorder.
Psychotic, bipolar, dissociative identity, or eating disorders.
\* suicidal risque with C-SSR score ≥4
Pregnancy and/or breastfeeding.
Patients subject to legal guardianship and/or other circumstances rendering the patient unable to understand the nature, purpose or consequences of the study.
Contraindication to the use of MEOPA and any condition where air is trapped inside the body and where its expansion could be dangerous: pneumothorax, emphysema, intestinal obstruction, intracranial hypertension, known and untreated deficiency of vitamin B12 or B9 (based on a test result less than 1 month old), Patients requiring ventilation with pure oxygen; any impairment of consciousness preventing patient cooperation; head injury; Gas embolism; Diving accident; Abdominal gas distension; Patient who has recently received an ophthalmic gas (SF6, C3F8, C2F6) used in eye surgery (as long as a gas bubble persists inside the eye and for a minimum period of 3 months), neurological abnormalities of recent or non-recent onset.
Sub-physiological plasma concentration of vitamin B12 or B9 (below the lower limit of the laboratory's reference range).
Supraphysiological plasma concentration of homocysteine (above the upper limit of the laboratory's reference range).
