The investigator proposes to use the cardiac coherence technique to diminish anxiety before the surgery of a peritoneal carcinosis of colon or stomach or ovary and pseudomyxoma or peritoneal mesothelioma.

Facing a Peritoneal Carcinomatosis (PC) diagnosis requires significant psychological adjustments that may generate major distress because of heavy care and a sometimes poor prognosis. Psychological distress, which most frequently results in emotional anxiety and depressive disorders, affects nearly 40% of patients in oncology. These disorders impair their quality of life, their health behaviours, their therapeutic alliance with caregivers, and represent a risk factor for mortality since access to care, lifestyle and therapeutic adherence differ. All learned societies (e.g., American Society of Clinical Oncology - ASCO), associations (e.g., Union for International Cancer Control (UICC), World Cancer Research Fund International - WCRF) and authorities (e.g., French National Institute of Cancer) recommend both the screening and treatment of this psychological distress. This complementary therapy should be integrated in the overall management of cancer patients, especially since anxiolytics (e.g., benzodiazepines) have shown limitations in clinical trials compared with placebo or standard care. Studies evaluating relevant psychological interventions to treat these disorders are rare. It is therefore essential to assess the feasibility and relevance of implementing a non-drug intervention known for its anxiolytic and antidepressant effects, to respond early and appropriately to the distress and anxiety of patients with PC before and after their surgery. Among the various existing non-drug interventions, a targeted cardiac coherence program seems promising. Cardiac coherence corresponds to a physiological state of balance of the autonomic nervous system obtained through precise and rigorous breathing exercises. Several pilot studies justify its interest in oncology. The main objective of this study is to evaluate adherence to a cardiac coherence program aimed at reducing anxiety in patients with PC awaiting cytoreductive surgery. The secondary objectives are to evaluate the implementation of this program in a cancer center, its adoption by the patients and the impact of this practice on their anxious symptomatology, immunological response and quality of life.

Inclusion Criteria:

1. Age over 18 years
2. Patients with peritoneal carcinosis awaiting cytoreductive surgery
3. Patients who scored strictly above 3 on the visual analogue anxiety scale and/or the psychological distress scale
4. Patients with sufficient command of the French language
5. Patient affiliated to a French social security system
6. Patient hospitalized at the Institute of cancer of Montpellier the day before his cytoreductive surgery (at T1 = D-1)
7. Signing of informed consent before any specific trial procedure

Exclusion Criteria:

1. Patients who already have daily practice of cardiac coherence
2. Presence of proven psychiatric disorders (e.g., mental retardation, psychotic disorders, learning disabilities, attention deficit/hyperactivity, bipolar disorder, etc.) other than mood disorders that are reactive to the disease experience, or receiving psychotic treatment that may impair thinking, judgment or discernment
3. Physical or sensory inability to respond to questionnaires
4. Patients who have had a heart transplant or bypass surgery in the Year before surgery
5. Patient with a history of uncontrolled neurological pathology within the last 6 months before inclusion in the trial
6. Patients with a history of psychoactive substance dependence (excluding smoking) in the last 6 months before inclusion in the trial
7. Patients with brain metastases
8. Known natural bradycardia 50 beats per minute
9. Beta-blocker intake in progress
10. Ongoing cardiac arrhythmias
11. Known severe heart failure with ventricular ejection fraction strictly Below 40 %
12. Chronic uncontrolled pain and making it difficult to practice the technique
13. Patient with chronic obstructive pulmonary disease
14. Legal incapacity (patient under guardianship or curatorship)

All data will be available after publication of the results in peer-reviewed revues, and in national and international meetings. It includes all disidentified participants' data, the study protocol, the statistical analysis plan and analytic code. The corresponding author will provide data and datasets generated and/or analyzed during the study upon reasonable request.

Access to study data upon written detailed request sent to ICM, following publication and until 5 years after publication of summary data.

The data shared will be limited to that required for independent mandated verification of the published results, the applicant will need authorization from ICM for personal access, and data will only be transferred after signing of a data access agreement.