An assesment of an optical system that measures blood pressure on the finger -Elfor 1 device. The system is based on a small optical sensor that emits coherent light into the skin and collects the reflected light from the red blood cells in the blood vessels in the skin under the sensor. The sensor is able to detect the pulse wave and blood pressure can be measured.

The investigators plan to measure blood pressure with the new sensor in patients who are attending the Hypertension Clinic at Meir Hospital or are undergoing hemodialysis to validate the sensor.

If the blood flow is temporarily interrupted by inflating a small pneumatic cuff at the root of the finger, blood flow is occluded and the pulse wave disappears. As the pressure in the cuff is released, blood flow returns, the pulse wave is again detected and blood pressure can be measured. This apparatus is easy to use and will allow simplified monitoring of blood pressure contains the laser source and optical sensors that measure the reflected light.

The investigators proposed to validate the sensor by measuring the blood pressure in patients with this optical sensor and also by standard plethysmography. The investigators plan to measure participants with low, normal and high blood pressure in order to assess the accuracy and reliability of the new device.

Inclusion Criteria:

• patients on hemodialysis or visiting the hypertension outpatient clinic at Meir Medical Hospital.

Exclusion Criteria:

-