Shows the effect of increases in cardiac output (independent variable) on right atrial pressure (dependent variable)
aka static pressure [BL8]
aka mean circulatory pressure [BL8]
aka mean systolic filling pressure [PK1]
[KB2:p103] ... a theoretical pressure that is said to represent the force promoting venous return.
[PK1:p136] MSFP is (proposed by Guyton)... the average of all the pressures in the different vessels weighted according to their relative compliances.
--> MSFP approximates to mean venous pressure
Normal value ~ 7mmHg
Basically, my understanding is:
Mean systemic pressure is the mean pressure exerted by the volume of blood alone, at a given vascular system (and vessel compliances) without any contribution from the heart, or any activation of compensatory reflexes.
Mean systemic pressure increases with:
Not significantly affected by total peripheral resistance
* Because arterioles which contribute the most to resistance only contain very little blood (1-2% of total blood volume)
NB:
Compliance of arteries to veins
~ 1:19
When cardiac output increase, blood is moved from venous circulation to arterial circulation
Increase in arterial blood volume
= Decrease in venous blood volume
However, because of the differences in compliance
--> Increase in arterial BP is 19 times the decrease in venous BP
[BL8:p203-205]
[##20050614(01)]
dPa = -19 x dPv
R = (Pa-Pv)/Qr
--> Pv = - [R.Ca/(Ca+Cv)]Qr + Pmc
Thus, slope of the curve is only dependent on:
--> MSP increased, gradient unchanged
--> Vascular function curve moves up
--> MSP unchanged, gradient decreases
--> Vascular function curve rotate downwards
--> MSP increased (due to venoconstriction), gradient decreased (due to vasoconstriction)
--> Vascular function curve shifts upwards and slope flatter
--> MSP increased (due to fluid retention), gradient unchanged
--> Vascular function curve shifts upwards
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Reviewed | 20050816 |