several guidelines have been published regarding the treatment and prevention of deep vein 
 thrombosis ( dvt)1 , 2 .
the guidelines underscore the fact that comprehensive measures for 
 prevention of dvt are necessary3 . 

guidelines for the diagnosis , treatment and prevention of pulmonary thromboembolism and deep 
 vein thrombosis ( jcs 2009)2 state that 
 elastic stockings are effective for the prevention of dvt . the mechanisms by which wearing 
 elastic stockings prevents dvt are prevention of blood stasis by increasing the blood flow 
 volume and decrease of the caliber of venous blood vessels by compression of the lower 
 limbs4 . however , these effects are still 
 under debate5 , 6 .
nara et al . reported that there is little effect when elastic 
 stockings are used as a single application7 , but scurr et al . indicated that a combination of elastic stockings 
 and intermittent pneumatic compression was effective for prevention of dvt8
therefore , examination of the effects of 
 combining elastic stockings with something else on prevention of dvt may be of clinical 
 significance .
previously reported that ankle positions affect the blood velocity 
 in the common femoral vein during ankle pumping exercises9 , which was recommended for the prevention of dvt .
the aim of this study was to identify how to effectively use elastic stockings to change 
 the blood flow velocity in the common femoral vein under different ankle positions .
the study subjects were 10 males without a history of cardiovascular diseases and no 
 contraindications for exercise testing and training according to the guidelines of the 
 american heart association10 .
one experimenter ( y.f . ) measured the blood flow velocity in all of these experiments . 

time - averaged maximum flow velocity ( tamv ) in the left common femoral vein was measured 
 using a pulse doppler method with a diagnostic ultrasound system ( acuson p300 , siemens 
 healthcare , erlangen , germany ) .
tamv is the averaged blood flow velocity per unit time in 
 the left common femoral vein . the subject s heart rate , systolic blood pressure ( sbp ) , and diastolic blood pressure ( dbp ) 
 were monitored ( suntech tango+ , suntech medical , usa ) continuously during measurement of 
 tamv . in this study ,
stocking were used , and 
 the right size for each subject according to the instruction manual was selected .
subjects were asked to assume 
 three different positions : supine ( supine position ) , supine with the legs up after the 
 examination bed was raised to an 18-degree angle ( leg - up position ) , and supine with the head 
 up after the examination bed was raised to a 30-degree angle ( head - up position ) ( fig .
1.experimental protocol ) . at the beginning of each condition , the subjects had a 3-min rest period to 
 acclimatize themselves to each position .
after the 3  min of rest , the tamv in the left 
 common femoral vein was measured for 20 seconds . in total , the subjects were asked to 
 undergo testing under six conditions , that is , each of the 3 positions with and without 
 stockings .
experimental protocol two - way anova for repeated measures was used to compare the tamv values of blood flow 
 velocity .
all analyses were 
 performed using spss statistics ver . 17.0 ( spss inc . , chicago , il , usa ) , and statistical 
 significance was accepted at an alpha level of 0.05 .
this study was approved by the human ethics review of tokyo university of technology 
 ( approval number ; e14hs-026 ) .
under the without stockings condition , the tamv in the head - up position ( 16.6  6.1  cm / sec ) 
 was significantly lower than those in the supine ( 30.1  17.8  cm / sec ) and leg - up positions 
 ( 28.9  17.5  cm / sec ) ( supine vs. head up , p<0.05 , leg up vs. head up , p<0.05 ) .
tamv 
 showed no significant difference between the supine position and leg- up position ( table 1table 1.time-averaged maximum flow velocity in the common femoral vein in three different 
 positions with and without stockings ) . under the with stockings condition , the tamv in the head - up position ( 13.6  
 4.4  cm / sec ) was also significantly lower than those in the supine ( 33.1  15.5  cm / sec ) and 
 leg - up positions ( 27.7  9.4  cm / sec ) ( supine vs. head up , p<0.01 , leg up vs. head up , 
 p<0.01 ) .
tamv showed no significant difference between the supine position and leg - up 
 position ( table 1 ) .
in this study , elastic stockings did not affect the blood flow velocity in the common 
 femoral vein .
this can be attributed to the fact that subjects were young health males who 
 had no problem in their venous valves and venous vascular walls .
generally , the venous 
 diameter is wider than the arterial diameter , but the venous vascular wall is thinner than 
 the arterial vascular wall because it has a thinner layer of smooth muscle and fewer elastic 
 components .
for this reason , veins have great compliance and thus a high blood volume , and 
 compression can easily change the venous shape11 . in venous incompetence ,
the number of collagen fibers increases , 
 and the fibers are randomly aligned12 , 13 .
furthermore , veins can not constrict and 
 expand adequately in response to the stimulation of noradrenalin , potassium chloride , 
 angiotensin ii , nitric oxide , calcium ion , etc . , and they do not function normally14
. additionally , expansion of veins and 
 blood stasis occur easily because dysfunction of venous valves causes the blood pressure to 
 increase in veins .
thus , it is likely that elastic stockings are effective in preventing 
 blood stasis in venous incompetence by compressing veins continuously and preventing them 
 from expanding15 . in this study ,
therefore , it is suspected that compression by elastic 
 stockings does not lead an increase in blood flow velocity , as their venous valves and 
 venous vascular walls functioned properly . on the other hand ,
it is 
 known that an increase in hydrostatic pressure disturbs venous return16 , thus in venous incompetence , the blood velocity in the 
 common femoral vein can decrease markedly because venous incompetence disturbing venous 
 return may be affected profoundly by gravity .
this study has some limitations : ( 1 ) the number of subjects in this study was relatively 
 low , and ( 2 ) the subjects were only young healthy male volunteers .
this could have affected 
 results , and a study for different age groups of people should be performed .
 [ purpose ] the aim of this study was to identify how to effectively use elastic stockings . 
 [ subjects and methods ] ten young healthy men participated in this study . 
 time - averaged 
 maximum flow velocity in the common femoral vein was measured for 20 seconds using a pulse 
 doppler method with a diagnostic ultrasound system under six conditions ( three different 
 positions and with and without stockings ) . 
 changes of blood flow velocity were compared . 
 
 [ results ] elastic stockings did not affect the blood flow velocity in the common femoral 
 vein . for both the with stockings condition and without stockings condition , the 
 time - averaged maximum flow velocity in the head - up position was significantly lower than 
 that in the supine and leg - up positions . 
 time - averaged maximum flow velocity showed no 
 significant difference between the supine position and leg - up position . 
 [ conclusion ] 
 elastic stockings did not affect the blood flow velocity in the common femoral vein , but 
 ankle positions did affect it . 
 further studies of patients with venous insufficiency are 
 needed . 