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 how decreased TPR affects ,,,,  



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Author18 Posts
  #1

diastoli BP

systolicBP

PULSE PRESSURE




  #2

ok ,i am not sure but i think;

when TPR DECREASE;

systolic increase

diastolic decrease

pulse pressure increase

any one wants to correct ,discuss or add? pleaaaase do. cause i have found this concept as basic for many questions


  #3

The main parameter affected is diastolic BP.It decreases.

Fall in TPR also means better compliance.Which means a fall in systolic BP.

So pulse pressure either stays the same or decreases.


  #4

Low TPR = Septic shock

In Septic shock

SBP falls
DBP falls
Pulse pressure falls

As a result, the patient falls out of bed


  #5

doc.aparna "Fall in TPR also means better compliance.Which means a fall in systolic BP" does not seem true ,bc kaplan specificly says, when compliance decrease; disatolic BP decrease and systolic INCREASES

i also know when stroke volume increase both systolic and diastolic increase but more systolic ,therefor PP increases(again from kaplan),,,,so my confusion is here,since TPR is decreased SK increases so systolic BP should increase,,,,

for diastolic one,it slightly increase via stroke volume but it is also affected by TPR and b/c TPR IS low so overall diastolic BP dcerease
Dr.Aparna wrote:
The main parameter affected is diastolic BP.It decreases.

Fall in TPR also means better compliance.Which means a fall in systolic BP.

So pulse pressure either stays the same or decreases.



  #6

an example of dereased TPR is anemia-low viscosity reduces TPR- and we have wide PP(pulse pressure)

please continue to discuss, we learn thru sharing


  #7

Compliance is not directly related to TPR.

Compliance = delta V / delta P

The scenario you were referring to was Arteriosclerosis, i.e. decrease in vascular compliance due to calcification, leading to high pulse pressure, high SBP typically seen in the elderly.

The increased PP in anemia is not due to a fall in TPR (even though fall in viscosity does reduce TPR, it matters very little) but rather an increase in cardiac contractility as a compensation to low O2 delivery.

If by dr. Aparna, you meant the guy who teaches physiology on the Kaplan video lectures, then I'm sorry to tell you, he is an idiot.


  #8

And come on, how can you possibly have an increased SBP when TPR falls?

Are you telling me, if you were to give Phentolamine (the preOp Rx for Pheo) you are actually going to raise the SBP and kill the patient?


  #9

@doctorforever better compliance doesn't mean decreased compliance.It means increased compliance.Increased ability to accomodate changes.If a vessel is persistently constricted(increased TPR), it is a stubborn one.It wont accomodate an increased cardiac output and systolic BP will increase.

If your cardiac output increases due to the fall in TPR (which can also mean fall in afterload), the vessels are more capable of accomodating that increase (remember increased compliance?). So your systolic BP wont increase, it will decrease.

Don't mix up anaemia here.Anaemia doesn't have much to do with TPR.It's problem is Decreased O2.


Edited by Dr.Aparna on Apr 08, 2010 - 5:54 PM

  #10

dr.knivessmiling face i am not sure which doctor u r refering in kaplan audios but if u r talking about the one who passonately talks about" ATTATCHING" sites of myosin and that wedding story,,,he IS a terrible teacher in my opinion......but by dr.aparna u see i meant this nice member of forum who is sharing her knowlege and she is greatsmiling face

and thank u for contributing ,u r so right when tpr is low we can not expect high systolic preesure,,

well doc.aparna i knowthat beter compliant means greater comoliant-maybe the way i typed was not right,,,

thanks for your nice explanation ,so i understand that when TPR is decreased although SV is increased but it can not fully compensate and systolic BP is low as well as diastolic

about anemia i still do not understand ,why PP increase!

also how would u explain wide PP in PDA,,,,is not that true that in PDA TPR is low ,b/c aorta is connected to a lower resistant system (pulmonary arteries)?

LET'S discuss,discuss,discussnod


  #11

A 65-year-old male visits his family practitioner for a yearly examination. Measurement of his blood pressure reveals a systolic pressure of 190 mm Hg and a diastolic pressure of 100 mm Hg. His heart rate is 74/min and pulse pressure is 90 mm Hg. A decrease in which of the following is the most likely explanation for the high pulse pressure?
A. Arterial compliance
B. Cardiac output
C. Myocardial contractility
D. Stroke volume
E. Total peripheral resistance

correct answer is a,,,now who can tell me why diastolic bp is not dcereased ? we know when compliance decrease diastolic decrease and systolic increase. then why this quy does not have lower diastolic bp?


  #12

I know that there is something called ISOLATED SYSTOLIC HTN that occurs with reduced compliance of atherosclerosis. But I get very confused when I try to work it out confused


  #13


Dear Drforever
To your post 4/ 7/2010

Decrease in TPR

Systolic blood pressure decreases due to the fact that arteries dilate. less resistance. simple.

Diastolic blood pressure -------> decrease in TPR will cause increase venous return ( dilated arteries so more blood flow to heart) , but right atrial pressure will not change... because according to frank starling law ... all the pumped blood in heart goes back into circulation ... So diastolic decreases only to slight extent ( because more blood is in arteries instead of right atrium) or remains unchanged ( because of venous return)

Now since Systolic decreases more than Diastolic when TPR decreases you will get a Decreased Pulse Pressure...

These 3 things you asked in original question






  #14

About 65 year old man ...

Are u sure the answer is arterial compliance
i disagree

i think The most important determinant of Pulse pressure is stroke volume ( answer D)

Not arterial Compliance

Arteries are very less compliant even in young age... Why wud old age make it any worse ? Veins are the compliant ones...

what do you think ?


On Apr 23, 2010 - 7:10 PM, doctorforever responded:
i think since we have elastic tissue in b oth arteris and veins(ofcource more in veins) but still , so nomatter which vessel ,compliancy decrease in all


  #15

As for anemia

Decrease oxygen to tissues ------> hypoxemia-----> stimulation of peripheral chemoreceptors -----> sympathetic activity -----> increase contractility ------> increased cardiac output ------> increased stroke volume ( which determines pulse pressure) ----> Change in systolic pressure due to increased stroke volume but diastolic unchanged ( no change in diastolic pressure occurs during ventricular contraction ) -----> increase pulse pressure

At least thats the mechanism for me ... feel free to discuss.. my two cents...



  #16

jekuter wrote:
As for anemia

Decrease oxygen to tissues ------> hypoxemia-----> stimulation of sympathetic activity -----> increase contractility ------> increased cardiac output ------> increased stroke volume ( which determines pulse pressure) ----> Change in systolic pressure due to increased stroke volume but diastolic unchanged ( no change in diastolic pressure occurs during ventricular contraction ) -----> increase pulse pressure

At least thats the mechanism for me ... feel free to discuss.. my two cents...




  #17

dear jekuter,

cardiac physiology never been an easy one for me ,there are so many ways to discuss mechanisms ,,so i tried to find a common way to solve problems for some of them;i might be wrong but since now it works for me fine to answer questions;

TPR; whenever TPR increase both sys and diast bp increase EQUALLY ,,so TPR HAS NO EFFECT ON PULSE PRESSUER(PP) .(i searched in so many reliable sites including the explanation of one of usmle queastions)

CHANGES IN TPR DOES NOT NECESSARY MEAN CHANGES IN COMPLIANCY( AS SOME REFER TO IT WRONGLY),when compliance decreases, as a result TPR is also decreased forsure ,but reverse is not true,i mean we can not say when we have vasoconstriction due to a drug it means we have less compliant vessel,no! we just have more tpr. compliance is about ELASTICITY of vessel wall (either arteries/veins) and it is a different concept.

compliance; when compliance increases diastolic bp increase but sys bp decrease so PP would be wide.

SV,,when sv increase both sys and diast bp increase but more systolic so PP increase

in anemia,,what u explained sounds right but i would like to stick to the fact that the main problem here that affects all CVS chnages starts from TPR,,in anemia TPR DECREAS (b/c viscosity is decreased) so both sys and diast bp decrease equally ..if it was supposed to stop here there would be no change in PP.but b/c SV increases(secendory to decreased tpr) so it tries to increase bp by increasing sys and diast bp both(again more syst) but compensation is never complete so sys and diastolic both are still low but diastolic is even lower that is why pp is increased.

in PDA; agaiin TPR is decreased(systemic vessels connected to low resistance pulmonary ones),here again SV increases but not only secendary to low TPR but also b/c all that blood that escapes systemic vessels and enters pulmonary vessels is quailcky going back to left heart (preload more) so sv is high for tow reason here so it can increase systolic bp ,actually in PDA we can have high systolic but still diastolic is low because SV effect on diastolic bp is very little.

so overall PP is high

other exampole is squatting; during squatte both femoral artery and vein are squeezed.so both TPR and SV(PRELOAD) are increased here increased in sv is not secendary to TPR , actually we expect to see decreased sv b/c of increased afterload, but b/c at same time preload is increased(b both arteris and VEINS at same time are squeezed) so here SV can can increase systolic bp (same changes as PDA)


SO how i approach these kind of queations is ,first see which factor is changed first.

second which are happening simultanously, and which is seconday to other,,,,


my logic might sound strange and complicated but as i said this works for me ,i might find it not practical and later change it .

about the answer of that old guy ,yes i double checked it answer is A.

and thank you for posting here smiling face




jekuter wrote:




Edited by doctorforever on Apr 23, 2010 - 7:19 PM

  #18

.. yes my bad.. its a .. cuz a decrease in stroke volume cant increase pulse pressure.. it would be arterial compliance.

I found out .. that pulse pressure depends on 2 factors
Stroke volume and compliance of aorta
In old age... aortic compliance decreases ... that would lead to increase in pulse pressure because
more the compliance----------> smaller the pressure change to accommodate blood in aorta

So in essence systolic pressure rises and pulse pressure increases

You ask why diastolic does not change. ... I think thats the reason i found....
Pulse pressure determinants are just 2
1. Stroke volume -----> increase leads to increase in systolic pressure and PP
2. Aortic compliance-------> decrease leads to increase in systolic pressure and PP

Diastolic pressure for all practical purposes does not affect Pulse pressure in physiological terms .. unless off course we talk about pathological states in which diastolic pressure would change

Your comments welcome....


On Apr 26, 2010 - 8:02 PM, doctorforever responded:
thanks for inputs jekuter,,i just want to know if you are sure about this part of your statement *Diastolic pressure for all practical purposes does not affect Pulse pressure in physiological terms .. unless off course we talk about pathological states in which diastolic pressure would change* cause kaplan note clearly says when compliance change both sys and dia change (opposite directions) thanks again





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