There is provided a device for estimating a compliance of a blood vessel in a subject, the device comprising a blood volume sensor for measuring changes in blood volume in skin of the subject and for outputting a blood volume signal； an actuator arranged to selectively apply a force on the blood volume sensor and press the blood volume sensor onto the skin； a force sensor for measuring the force applied to the blood volume sensor and for outputting a force signal； and a control unit. The control unit is configured to receive a blood volume signal and a force signal for a time period in which the actuator increases the force applied on the blood volume sensor from a first force to a second force； determine a pulse pressure from the blood volume signal and the force signal, wherein the pulse pressure is the difference between a first blood pressure of the subject and a second blood pressure of the subject； process the blood volume signal to identify cardiac cycles and determine a blood volume amplitude for each cardiac cycle in the time period from the blood volume signal； determine, for each cardiac cycle, a ratio of the blood volume amplitude for the cardiac cycle and the determined pulse pressure； form a set of ratios from the determined ratios； and estimate the compliance of the blood vessel as a function of the set of ratios.
