Abstract: A device providing physiological protection of aircraft pilots against the effects of altitude and accelerations includes a source of oxygen; a chest jacket fitted with at least one inflation bladder connected to a pressure reducing valve installed on a source of gas under pressure by a pipe; an oxygen mask connected to a source of oxygen by a conduit and a pressure reducing valve. The anti-g trousers include at least one inflation bladder connected to a pressure reducing valve, the bladder being mounted on a source of gas under pressure. The device further includes a mechanism to detect accelerations which delivers a signal representative of the acceleration. The device is characterized by a deformable volume located inside the inflating bladder of the chest jacket connecting the mask to the source of oxygen.