The present disclosure relates to a method and system for assessment of a blood flow in an area of the skin and underlying tissue of a patient. The method comprises a step of subjecting the assessed area to at least two different pressure states, wherein the different pressure states are obtained by the patient's weight pressuring against a support on which the patient is placed and an expandable element at least partly circumventing the assessed area and expandable a direction from the support against the patient to substantially eliminate a patient's body from the support in the area at least partly circumventing the assessed area. The method further comprises the steps of obtaining (S8) blood flow data related to the assessed area while subjecting the assessed area to the at least two different pressure states, wherein the blood flow data is obtained by means of photoplethysmography and assessing (S9) the risk of pressure ulcers on the patient based on assessment of the blood flow data obtained for the at least two different pressure states.
