 Already in 1981, Judy did a study showing that the transthoracic electrical impedance method for measuring cardiac output in humans warranted further consideration as a non-invasive clinical tool that will be applicable in the investigation of the hemodynamics of normal and altered physiological states.As a graduate student and NIH fellow at Baylor University Medical School (1963), Judy was introduced to the bioelectrical impedance method as a noninvasive means of measuring stroke volume and cardiac output.He helped develop this method for space flight in 1964 and 1965.