What is blood viscosity is increased? Cold application?
Answers
Relationship of Blood Temperature, Viscosity, and Pressure
When the blood temperature decreased from 36.5° to 22°C, the mean blood free flow time increased from 11.62 to 15.55 sec (26.13%). According to Poiseuille's equation, the blood flow rate decreases 20.72%, and for the compensation of this ischemic state, a 26.13% BP increase or 5.9% vasodilation is needed. If viscosity (η in the denominator of the equation) changes from 100 to 126.13 (26.13%), the flow rate Q would decrease 100/126.13 = 20.72%. If viscosity increases 26.13%, the pressure (F1 − F2) value (multiplier in the equation) must be increased with the same percentage to keep the equation constant. When the viscosity increases 26.13%, to keep the flow rate constant, the radius of vessel (initial) a4, must increase 26.13%. The calculation of this increased radius (final) is a4final = 1.2613 × a4initial. From this calculation, αfinal = forumla = 1.0597 and so, 5.97% vasodilation can be estimated.
When the temperature increased from 36.5° to 39.5°C, the blood free flow time decreased from 11.59 to 10.58 sec (10.38%). In this state, the blood flow rate increased 11.15%; according to Poiseuille's equation, a 10.38% decrease in BP or 2.71% vasoconstriction was needed to keep the hemodynamic equilibrium constant.
The correlation between temperature and blood viscosity is r = −0.84, P < .001 when all the differences at the three temperatures are evaluated together (Fig. 1). When all of the blood free flow time data for the three temperatures were evaluated together according to age, there was a negative correlation (r = −0.1381 and P < .05); when the data were evaluated according to sex, it was found that the mean blood free flow time in women was 12.97% less than that in men (r = 0.3408, P < .001).
Effect of temperature on blood viscosity. When blood temperature decreases from 36.5° to 22°C, blood viscosity increases 26.13%. If temperature increases from 36.5° to 39.5°C, blood viscosity decreases 10.38%. To make a more accurate presentation in the graphic representation and statistics, instead of the “relative viscosity” value, blood free flow time in seconds (s) was used as data. When all of the differences at three temperatures are evaluated together, a negative correlation is seen between blood temperature and viscosity (r = −0.84, P <