Effect of Systematic and Sequential Leg Elevation on Cardiac Output in Healthy Volunteers

Passive leg raising (PLR) transiently increases venous return and cardiac preload and is commonly used to predict fluid responsiveness in critically ill patients. Repeated fluid boluses contribute to fluid overload in septic shock, whereas PLR may provide similar hemodynamic effects without fluid administration. Before evaluating repeated PLR in septic shock patients, it is necessary to determine whether the cardiac output response to PLR remains present during repeated PLR maneuvers. SYSLE-1 is a prospective interventional physiological crossover study conducted in healthy volunteers. Participants will undergo six consecutive passive leg raising sessions performed either during spontaneous breathing or non-invasive ventilation, in randomized order. The study aims to determine whether the increase in cardiac output induced by the first PLR maneuver persists during repeated PLR sessions.

Inclusion Criteria: * Male or female participant. * Age 18 years or older. * Healthy volunteer without known acute or chronic disease. * No significant cardiovascular or respiratory disease. * No medication use within 10 days before the first study day (except oral contraceptives). * Intact upper and lower limbs. * Written informed consent. Exclusion Criteria: * Body mass index greater than 35 kg/m². * Use of illicit psychoactive substances within the previous 3 months. * Congenital or acquired absence of part or all of an upper or lower limb. * Known allergy to hydrocolloid dressings. * Pregnant or breastfeeding women. * Under guardianship, curatorship, or legal protection. * Deprived of liberty. * Not affiliated with a health insurance system. * Participation in another drug study during an exclusion period. * Member of the Lieu de Recherches Interventionnelles sur la Personne Humaine (LRIPH) or Intensive Care Unit staff. * Refusal to participate.