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#1
02-21-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 121 Threads: 18 Thanked 66 Times in 37 Posts Reputation: 76
Pulse Pressure and Vessel Compliance

In my understanding, if vessel compliance is increased, diastolic BP should decrease.
but in Kaplan notes, both 2008 and 10 version, they say, in case of pulse pressure, decreased vessel compliance = decreased diastolic BP.

kinda confused here. what am I missing?

thank you.
 The above post was thanked by: Sam imkeyim (08-12-2016)

#2
02-21-2011
 USMLE Forums Guru Steps History: 1+CK+CS+3 Posts: 335 Threads: 24 Thanked 296 Times in 152 Posts Reputation: 306

ok I'll try to break it down for you.

If a vessel is compliant, it means that volume changes cause less changes in pressure. If a vessel is less compliant, volume changes would cause a greater change in pressure. So in a less compliant vessel, during diastole when the volume decreases, the pressure drop is also greater and we get a lower diastolic pressure.

In mathematical terms, compliance= change in volume/change in pressure

If change in volume is constant, compliance is inversely proportional to change in pressure. So if a vessel is less compliant, the change in pressure (or drop in pressure in case of diastole) is larger.
 The above post was thanked by: bronchiole (02-21-2011), maksemous (11-05-2012), Mondoshawan (02-21-2011), Sam imkeyim (08-12-2016), tarsuc (01-30-2016), wimzie (02-21-2011)
#3
02-21-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 121 Threads: 18 Thanked 66 Times in 37 Posts Reputation: 76

First of all, thanks for your time.

I don't have any problem understanding that. I mentioned that in my post. I am just confused when they are mentioning pulse pressure ,they are saying the exact opposite of what you/I said and that is in both editions. Hence, my confusion.

but according to your explanation, if I consider pulse pressure,
pressure change (systole has to increase and diastole has to decrease) increased and volume change is constant, only then i can think that decreased vessel compliance comes with decreased diastolic.

Please give a response on it.

#4
02-21-2011
 USMLE Forums Guru Steps History: 1+CK+CS+3 Posts: 335 Threads: 24 Thanked 296 Times in 152 Posts Reputation: 306

OK I am not sure I understood your question but if I did, you got it right.

Pulse pressure= systolic pressure-diastolic pressure

So decreased compliance will lead to high systolic and low diastolic, means large difference and large pulse pressure.
 The above post was thanked by: maksemous (11-05-2012), Mondoshawan (02-21-2011), steps (02-21-2011)
#5
02-21-2011
 USMLE Forums Master Steps History: 1+CK+CS Posts: 590 Threads: 31 Thanked 1,233 Times in 411 Posts Reputation: 1257

Quote:
 Originally Posted by bronchiole In my understanding, if vessel compliance is increased, diastolic BP should decrease.
I think this is where you're backwards.

What doctorsmonters wrote is correct: a fixed stroke volume going into a vessel with decreased compliance results in a greater pulse pressure - that is to say, a greater gap between systolic and diastolic pressures. Systolic pressure goes up with decreased compliance and diastolic goes down.

hope that helps?
 The above post was thanked by: bronchiole (02-22-2011), conspicous (02-21-2011), doctorsmonsters (02-21-2011), tarsuc (01-30-2016)
#6
02-22-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 121 Threads: 18 Thanked 66 Times in 37 Posts Reputation: 76

Quote:
 Originally Posted by Mondoshawan I think this is where you're backwards. What doctorsmonters wrote is correct: a fixed stroke volume going into a vessel with decreased compliance results in a greater pulse pressure - that is to say, a greater gap between systolic and diastolic pressures. Systolic pressure goes up with decreased compliance and diastolic goes down. hope that helps?
yeah,that is exactly what I said in my 2nd post.thanks for your input.
#7
02-22-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 121 Threads: 18 Thanked 66 Times in 37 Posts Reputation: 76

Quote:
 Originally Posted by doctorsmonsters OK I am not sure I understood your question but if I did, you got it right. Pulse pressure= systolic pressure-diastolic pressure So decreased compliance will lead to high systolic and low diastolic, means large difference and large pulse pressure.
thanks a lot.I am glad that it is now clear to me.thank you sooo much.
 The above post was thanked by: doctorsmonsters (02-22-2011)
#8
02-22-2011
 USMLE Forums Guru Steps History: 1+CK+CS+3 Posts: 335 Threads: 24 Thanked 296 Times in 152 Posts Reputation: 306

 The above post was thanked by: bronchiole (02-22-2011)
#9
07-30-2011
 USMLE Forums Addict Steps History: 1+CK+CS Posts: 158 Threads: 33 Thanked 10 Times in 9 Posts Reputation: 20

Thanks for your explanations mentioned above, it really helped. But can someone help me apply those rules into valvular disease !

What is the mechanism behind wide pulse pressure in Aortic Regurgitation and narrow pulse pressure in Aortic stenosis ?

Aren't Both supposed to have wide (high) pulse pressure because in case of Aortic stenosis systolic pressure increases and diastolic pressure decreases, while in case of regurgitation diastolic pressure decreases due to less blood volume.

 Tags Cardiovascular-, Physiology-

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