Non-invasively measuring a physiological parameter by applying to a subject'sbody part a venous occlusion plethysmographic device including a first sectionhaving a first fluid chamber and at least a second region having a secondfluid chamber to engage a first region of the body part and a second region ofthe body part, proximal of the first region； pressurizing the first chamber toa pressure sufficient to compensate for hydrostatic pressure added to theinherent venous pressure at the maximal vertical lowering level of the bodypart relative to the subject's heart level； intermittently raising andlowering the pressure in the second fluid chamber to a pressure above or equalto the pressure in the first chamber, but below the arterial blood pressure；measuring changes in volume of the first region of the body part； andutilizing the measured volume changes to provide a measure of thephysiological parameter.
