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 04-24-2012, 06:09 PM #1 1K Member   Status: Medical Student Join Date: Nov 2007 Posts: 1,455 know any formulas to calculate systolic and diastolic bp? SDN Members don't see this ad. (About Ads) I got pimped today about this and the only thing I could think of was rearranging map = 2/3 Dbp + 1/3 Sbp. Any other suggestions?
 04-24-2012, 06:23 PM #2 Senior Member     Status: Medical Student Join Date: Jul 2008 Location: la la land Posts: 262 You can't calculate systolic and diastolic pressures. Its something you measure (ie with a BP cuff). You can calculated Mean Arterial Pressure.
04-24-2012, 06:28 PM   #3
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Quote:
 Originally Posted by cliquesh I got pimped today about this and the only thing I could think of was rearranging map = 2/3 Dbp + 1/3 Sbp. Any other suggestions?
Yea that would give you one equation with 2 unknown variables. You can't do that.
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 Originally Posted by VisionaryTics They get access to Robbins' Pathologic Basis of Disease, Yale Edition: The Real Medicine

 04-24-2012, 06:30 PM #4 1K Member   Status: Medical Student Join Date: Nov 2007 Posts: 1,455 It was a cardiologist that asked me this question. He said he is going to ask me again tomorrow and he wants specific equations, but i cannot find anything. he wants two equations, one for DBP and one for SBP
 04-24-2012, 06:43 PM #5 Senior Member   Status: Medical Student Join Date: Mar 2010 Posts: 590 bp cuff plus arm = SBP/DBP
 04-24-2012, 06:45 PM #6 should have been dr. who     Status: Resident Join Date: Mar 2007 Posts: 320 Are you sure you understood him correctly? Does he have an accent?
 04-24-2012, 06:53 PM #7 Senior Member   Status: Medical Student Join Date: Jul 2010 Posts: 108 Yea. Press Start BP cuff on the f*cking monitor. Seriously, you should have said that.
 04-24-2012, 07:04 PM #8 MS4     Status: Medical Student Join Date: Apr 2012 Posts: 328 SBP = 110 + 2sqrt(age) + 20x, where x is number of antihypertensives pt. should take but doesn't No but seriously, your cardio attending should publish his miraculous method of calculating BP. We could save tons of money on BP cuffs. Actually wait, troll attending can be counter-trolled, observe: SBP = DBP + PP DBP = SBP - PP Last edited by DrSnips; 04-24-2012 at 07:13 PM.
04-24-2012, 10:39 PM   #9
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 Originally Posted by jcu Are you sure you understood him correctly? Does he have an accent?

Fun-ny.

But in all seriousness it could be a trick question..

04-25-2012, 12:47 AM   #10
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Quote:
 Originally Posted by AngleWold You can't calculate systolic and diastolic pressures
Thanks, I bet he hadn't deduced that yet from the 15 prior responses.

04-25-2012, 06:20 AM   #11
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Quote:
 Originally Posted by DrSnips SBP = 110 + 2sqrt(age) + 20x, where x is number of antihypertensives pt. should take but doesn't

 04-25-2012, 08:10 AM #12 Account on Hold   Status: Medical Student Join Date: Feb 2012 Posts: 8,013 Find 2 theoretical calculus proofs on fluid dynamics. \$20 says he can't tell you you're wrong
04-25-2012, 08:20 AM   #13
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Quote:
 Originally Posted by SpecterGT260 Find 2 theoretical calculus proofs on fluid dynamics. \$20 says he can't tell you you're wrong
\$20 says he asks you to explain those proofs

 04-25-2012, 08:29 AM #14 Avatar of Boris     Status: Medical Student Join Date: Apr 2011 Location: OH Posts: 668 DBP = Force of Blood in Brachial Artery / Area of Brachial Artery during Diastolis There you go. __________________ "If you ask me for an apple and I give you an orange you would say, that's not an orange. And I say, that's a banana. And that's not an apple either. Or a peach, that's not an apple, either. It doesn't mean that I'm equating the banana and the orange and the peach." - Dr Ben Carson, Brainsurgeon.
04-25-2012, 08:31 AM   #15
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 Originally Posted by cliquesh I got pimped today about this and the only thing I could think of was rearranging map = 2/3 Dbp + 1/3 Sbp. Any other suggestions?
You can calculate systolic pressure with the modified Bernoulli equation: P = 4 * v^2. This is usually used with echo to estimate RVSP (right ventricular systolic pressure), but I suppose it could be used to estimate systemic pressure. You would have to add the result to the LAP (left atrial pressure), which you would have to measure or estimate.

 04-25-2012, 08:32 AM #16 4G MD     Status: Attending Join Date: Oct 2001 Posts: 1,419 Hope your attending's not an SDNer.
04-25-2012, 09:33 AM   #17
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Quote:
 Originally Posted by PMPMD You can calculate systolic pressure with the modified Bernoulli equation: P = 4 * v^2. This is usually used with echo to estimate RVSP (right ventricular systolic pressure), but I suppose it could be used to estimate systemic pressure. You would have to add the result to the LAP (left atrial pressure), which you would have to measure or estimate.
Hmmm. I see OP getting a paper out of this. Let me start it for you:

Title: A new method for determining systolic blood pressure by combined use of Doppler ultrasound and cardiac catheterization.

Abstract: Blah Blah insert statistics. The study showed that the new method of BP determination is non-inferior to use of conventional BP cuff when compared with arterial line measurements.

Methodology: We took 300 people who presented to a health fair for BP screening...

There you go OP, all I ask is that you not make me an author.

04-25-2012, 09:40 AM   #18
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Quote:
 Originally Posted by PMPMD You can calculate systolic pressure with the modified Bernoulli equation: P = 4 * v^2. This is usually used with echo to estimate RVSP (right ventricular systolic pressure), but I suppose it could be used to estimate systemic pressure. You would have to add the result to the LAP (left atrial pressure), which you would have to measure or estimate.
I should add that you would need to assume there is no significant AS (aortic stenosis) in this case.

The original concept is used in echo to estimate pulmonary arterial pressure:

PA ~ RVSP + RAP (or CVP) assuming no significant pulmonic stenosis

 04-26-2012, 11:20 AM #19 Senior Member   Status: Fellow Join Date: Jan 2010 Posts: 219 Also, the Dinamap (the typical automated BP cuffs you will see) or other automated BP cuffs use arterial pressure oscillation to get a mean arterial pressure, then calculate the measurements during the cycle to estimate a systolic and diastolic blood pressure. I'm sure if you read the technical specs of the Dinamap, they would show you how they derive a systolic and diastolic BP from a mean arterial pressure, though I doubt it is very straightforward.
 04-26-2012, 11:46 AM #20 1K Member     Status: Medical Student Join Date: Jul 2007 Posts: 1,933 How did it go OP?
04-26-2012, 12:42 PM   #21
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 Originally Posted by SurfingDoctor Also, the Dinamap (the typical automated BP cuffs you will see) or other automated BP cuffs use arterial pressure oscillation to get a mean arterial pressure, then calculate the measurements during the cycle to estimate a systolic and diastolic blood pressure. I'm sure if you read the technical specs of the Dinamap, they would show you how they derive a systolic and diastolic BP from a mean arterial pressure, though I doubt it is very straightforward.
Typically, the pressure resulting in the maximal oscillations is the MAP. Algorithms are used to calculate SBP and DBP from the MAP but these are generally proprietary.

I did find one published algorithm:

The Algorithm used by DINAMAP:

1. It first determines the amplitude at MAP, which is the lowest cuff pressure at which maximum amplitude is sensed

2. It then reviews the data above MAP and find the pressure that generates amplitude by 0.5 of the amplitude of MAP --> that is systolic blood pressure

3. Finally it reviews the data below MAP and find the pressures that generates amplitude by 0.625 of the amplitude of MAP --> that is diastolic blood pressure

04-27-2012, 01:54 PM   #22
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Quote:
 Originally Posted by PMPMD The Algorithm used by DINAMAP: 1. It first determines the amplitude at MAP, which is the lowest cuff pressure at which maximum amplitude is sensed 2. It then reviews the data above MAP and find the pressure that generates amplitude by 0.5 of the amplitude of MAP --> that is systolic blood pressure 3. Finally it reviews the data below MAP and find the pressures that generates amplitude by 0.625 of the amplitude of MAP --> that is diastolic blood pressure
I was wrong, that is totally straightforward.

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