A method for measuring at least one of stroke volume and cardiac output from a patient, comprising: operably connecting a processing system to both an impedance sensor and an optical sensor, the processing system being configured to be worn on the body; measuring a transbrachial electro-velocimetry impedance signal from the patient by positioning at least two electrodes connected to the impedance sensor on the patient in the clavicle/brachial region and by injecting a high-frequency, low amperage alternating current field along the course of the brachial artery in the clavicle/brachial region followed by simultaneously sensing and signal processing voltage changes produced within the current field, the impedance sensor comprising an impedance circuit configured to process signals from the at least two electrodes to measure the transbrachial electro-velocimetry impedance signal; measuring at least one optical signal from the patient by attaching an optical probe connected to the optical sensor to the patient, the optical sensor comprising an optical circuit configured to process signals from the optical probe to measure the at least one optical signal; and receiving the transbrachial electro-velocimetry impedance signal from the impedance sensor and processing it to determine a first value of at least one of stroke volume and cardiac output; receiving the optical signal from the optical sensor and processing it to determine a second value of at least one of stroke volume and cardiac output; and collectively processing both the first and second values of at least one of stroke volume and cardiac output to determine a third value of at least one of stroke volume and cardiac output. operably connecting a processing system to both an impedance sensor and an optical sensor, the processing system being configured to be worn on the body; measuring a transbrachial electro-velocimetry impedance signal from the patient by positioning at least two electrodes connected to the impedance sensor on the patient in the clavicle/brachial region and by injecting a high-frequency, low amperage alternating current field along the course of the brachial artery in the clavicle/brachial region followed by simultaneously sensing and signal processing voltage changes produced within the current field, the impedance sensor comprising an impedance circuit configured to process signals from the at least two electrodes to measure the transbrachial electro-velocimetry impedance signal; measuring at least one optical signal from the patient by attaching an optical probe connected to the optical sensor to the patient, the optical sensor comprising an optical circuit configured to process signals from the optical probe to measure the at least one optical signal; and receiving the transbrachial electro-velocimetry impedance signal from the impedance sensor and processing it to determine a first value of at least one of stroke volume and cardiac output; receiving the optical signal from the optical sensor and processing it to determine a second value of at least one of stroke volume and cardiac output; and collectively processing both the first and second values of at least one of stroke volume and cardiac output to determine a third value of at least one of stroke volume and cardiac output.