# narrowed pulse pressure



## emergancyjunkie (Aug 28, 2011)

why does a narrowed pulse pressure maintain adequate blood pressure for perfusion


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## LondonMedic (Aug 28, 2011)

In shock, a narrowed pulse pressure is usually attributed to decreased cardiac output either an inadequate preload in hypovolaemia or an obstructive problem such as tamponade.

However, vasoconstriction and the consequent reduction in vascular space can result in a narrower pulse pressure where the systolic value is normal and the diastolic raises.

This increases the mean arterial pressure (MAP = Diastolic Pressure + 1/3(Systolic Pressure - Diastolic Pressure) which is the measure of perfusion.


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## emergancyjunkie (Aug 28, 2011)

so that would Be a protective mechanism for bleeding internally or externally


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## LondonMedic (Aug 28, 2011)

emergancyjunkie said:


> so that would Be a protective mechanism for bleeding internally or externally


The latter would, yes.


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## emergancyjunkie (Aug 28, 2011)

ok it makes sense now


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## emergancyjunkie (Aug 28, 2011)

thanks for the explanation


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## usafmedic45 (Aug 28, 2011)

> an obstructive problem such as tamponade.


Which is another cause of inadequate preload.  Not trying to correct you or anything, just thought I would point that up.


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## Hunter (Aug 28, 2011)

Isn't it also a sign of pericardial tamponade?


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## usafmedic45 (Aug 28, 2011)

Hunter said:


> Isn't it also a sign of pericardial tamponade?



Among several other things, yes.


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## emergancyjunkie (Aug 28, 2011)

Ok can you explain when an emt-b use the tidal volume or minute volume equations


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## usalsfyre (Aug 28, 2011)

emergancyjunkie said:


> Ok can you explain when an emt-b use the tidal volume or minute volume equations



Your not generally going to be calculating minute volume at your level, but it's vital to understand the concept.


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## usafmedic45 (Aug 28, 2011)

There is no real "equation" for tidal volume, but if you have a specific minute ventilation you want to target, you simply figure up what the volume of each breath will be and divide that number into the minute ventilation to figure out the rate (or vice versa to determine the volume if you have a rate you want).  Honestly, given the lack of accuracy inherent in the devices used by EMTs and paramedics, it really isn't a huge issue.  Just remember not to bag too fast and/or too deep.  The rule I teach is 2-3 seconds for exhalation to every second you give for inhalation.


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## emergancyjunkie (Aug 29, 2011)

is that for a bvm cause I was told in airway management to count 4 to five seconds after the bag inflates again


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