In a publication1 on the prevention of pulmonary embolism some clinical evidence was brought forth to support the thesis that postoperative exercises are beneficial in preventing venous thrombosis. It was assumed that simultaneous deep breaths and active leg exercises taken at regular intervals would vary the blood flow in the pelvic venous cistern and "wash out" any accumulation of blood elements which might lead to beginning formation of thrombi. Although it was definitely stated in this publication that coincidence may have been a factor, in approximately 500 cases in which the patients took postoperative exercises there was no thrombophlebitis or pulmonary embolism. In 95 control cases of fractures of the back, pelvis, hip, femur or leg requiring complete immobilization there were 5 cases of thrombophlebitis, in 3 of which there were pulmonary emboli.
It is recognized that clinical application of a principle should follow experimental studies rather than deductive
POTTS WJ, SMITH S. PULMONARY EMBOLISMAN EXPERIMENTAL STUDY OF VARIATIONS IN THE VOLUME BLOOD FLOW IN THE INFERIOR VENA CAVA OF THE DOG. Arch Surg. 1941;42(4):661-664. doi:10.1001/archsurg.1941.01210100021002