A system and a method for applying a gradient of external compressive forces on the body of a person, in a manner analogous to how water exerts hydrostatic forces on the body of person immersed in water. The system may be a chair or a suit, comprising at least one of the following: one compression unit holding fluid around the person to exert a gradient of hydrostatic forces, at least one rigid or semi-rigid frame or a shell supporting the body and the compression units to support the pressure and off-loaded weight of the person and transfer the weight to an external support such as floor. Additionally, the system may contain additional means to reduce the frictional forces on the body surface and between various moving parts, and a means to modify pressure on the body of the person. The system and method is applicable for effecting physiological changes in the body such as increased diuresis and/or amniotic fluid levels, treat preeclampsia in pregnant women, reduce hypertension, shift fluids from interstitial space into intravascular compartment, increase venous return from lower extremities, reduce sympathetic tone and total peripheral resistance, reduce work load on the heart, reduce motion sickness and the like.L'invention concerne un système et un procédé d'application d'un gradient de forces de compression externes sur le corps d'une personne, d'une manière analogue à la manière dont l'eau exerce des forces hydrostatiques sur le corps d'une personne immergée dans l'eau. Le système peut être un fauteuil ou une combinaison (vêtement), comprenant au moins l'un des éléments suivants : une unité de compression maintenant un fluide autour de la personne pour exercer un gradient de forces hydrostatiques, au moins un cadre rigide ou semi-rigide ou une coque supportant le corps et les unités de compression pour supporter la pression et le poids non chargé de la personne et transférer le poids à un support externe tel que le sol. De plus, le système peut contenir des mo
