A bypass device for influencing blood pressure, including an implant with a volumetric chamber, having a connector or connecting means for connecting the volumetric chamber to a natural cardiovascular system, and having an adaptor or adaptation means, by which a change in volume of a volume of the volumetric chamber is enabled or effected upon a pressure change in the cardiovascular system or in the volumetric chamber. According to this invention, a change in volume in a lower pressure range between 50 mmHg and a pressure threshold value amounting to at least 100 mmHg amounts to at most 10 cm3, and in an upper pressure range between the pressure threshold value and 150 mmHg amounts to at least 10 cm3. With the device according to this invention, high blood pressure can be reduced in a carefully directed way.