Implanted electrodes can be used to deliver electrical stimulation signals to areas near blood vessels, nerves, or other internal body locations. In an example, an electrode can be implanted in a cervical location and can be used to measure dimensional changes in an artery using impedance plethysmography. Measured artery dimensional changes can be used to determine one or more physiological parameters associated with a patients health status, such as pulse transit time, relative pulse pressure, or aterial compliance, among others. These parameters can be used to monitor a patient health status or to modulate a patients therapy, among other uses. In some examples, an electrode configured to deliver an electrostimulation signal to nerve tissue can be used to provide non-neurostimulating electrical stimulation plethysmography signals near a blood vessel.
