[Physical flow studies of new surgical aspiration drains].

Mathematical and experimental results demonstrate that the customary Redon drain as well as the improved Neo-Redovac drain develop suction only over a short initial distance. The above mentioned innovation of three additional oval holes does not increase efficiency. The disadvantage of rapidly diminished suction is overcome in the "Ulmer Drain", in which equidistant openings of continually increasing aperture are aligned towards the drain end.