Carl Friedrich Wilhelm Ludwig was a German physician and physiologist. He is regarded as one of the leading physiologist of the second half of the 19th century. Ludwig's primary research interest was circulatory physiology. In 1846, Ludwig invented the kymograph to obtain recording of the blood pressure. Prior to this invention, the results of experiments were evaluated by visual observation.
He modified Poiseuille's manometer and connected a stylus to a float on a column of mercury in contact with a revolving smoke drum to graphically record physiological events.
Carl Ludwig was the first to obtain the recording of a physiologic event and his device was extensively used in experimental physiology.
This device also allowed the simultaneous observation of multiple events (respiratory rate, pulse rate, and blood pressure) leading to the discovery of physiological relationships between organs such as heart and lungs.
Because the recording of the pulse or arterial pressure required direct cannulation of the artery, this instrument was only used in experimental physiology. It is important to note, however, that current hemodynamic monitoring devices used in research or clinical practice can be traced to Ludwig's kymograph.
Fye WB. "Carl Ludwig and the Leipzig Physiological Institute: A factory of new knowledge." Circ 1986;74:920
Fye WB. Profiles in cardiology: Carl Ludwig. Clin Cardiol 1991;14:361-363