The invention concerns a physiological monitoring device that, in one embodiment, comprises a capacitive sensor. The sensor comprises a first plate, a second plate and a dielectric medium coupled to the first plate and second plate. A power source charges the sensor to generate an initial capacitance. A band couples the sensor to a blood vessel of a patient. For example, the blood vessel can be located in the umbilical cord of a human baby. An impulse from the blood vessel exerts pressure against the second plate of the sensor and consequently generates a first capacitance. A controller monitors the patient's physiological measurement by detecting the generation of the first capacitance.