A probe for application to a selected area of a subject's skin covering a bodypart, which selected area serves as a measurement site for measuring changesin the pulsatile arterial blood volume thereat, includes: a base forapplication to the selected area of the subject's skin at the measurementsite； a pressure applicator for applying a static pressure to the subject'sskin at the measurement site； and a sensor for sensing changes in thepulsatile arterial blood volume at the measurement site. The pressureapplicator is designed to apply to the measurement site a static pressure of amagnitude to partially unload the wall tension of, but not to occlude, thearteries. The pressure applicator is configured to substantially preventvenous distention and blood pooling at the measurement site by permitting freevenous drainage through tissues surrounding the measurement site. This is doneby configuring the pressure applicator to apply the static pressure to arelatively restricted area of the subject's skin, which area occupies arelatively small fraction of the surface perimeter of the respective body partat the measurement site, to thereby permit free venous drainage from themeasurement site via a wide region of unrestricted passageways surrounding themeasurement site.
