Blood Pressure Flashcards
BP usually means??
systemic arterial pressure.
BP term is quite variable, if over whole circuit, BP would be more ~7mmHg!
One modifiable factor that has the biggest effect on health and life expectancy
BP
What are the set values for high BP
There are none realistic one, it is a continuum. Increases CVD risk
Systolic BP (peak P) mean BP diastolic BP (minimum P)
Systolic BP: ~120
mean BP: ~100
diastolic BP: ~90
These tend to increase with age!!!
What does nun study show?
Effects of lifestyle: low stress, healthy diet, sleep etc leads to low BP that DOESN’T increase with age
MAP calculation?
1)
MAP = P(D) + 1/3 (Ps- PD)
MAP = Pd + 1/3PP
2)
MAP = CO x TPR
Pulse pressure (PP)
PP= Psys - Pdias
Whats so special about 100mmHg
is a relatively constant value for MAP for most mammals
**exception giraffes who have to push blood up neck
-Optimal pressure required at the capillary level to get sufficient fluid/blood drive for nutrient exchange.
If BP to high?
We increase resistance, but also get more fluid driven out of capillaries.
Leads to tissue damage and swelling
Draw BP = CO x PR diagram
…
Main determinants of systolic pressure
- SV (and ejection rate)
- aortic compliance
Main determinants of diastolic pressure
- Diastolic runoff: determined byHR, TPR
- Aortic compliance
Does arterial pressure get to zero?
NO. arterial pressure NEVER gets to zero, whereas ventricular pressures do! Need to maintain the pressure gradient!
Aortic Pulse Pressure
During systole: blood flows in, some moves on but due to the compliant nature of the vessel, it expands and some will be stored within the aorta
Aortic valve shuts: vessel springs back to shape and you still have flow continuing
SO flow through the WHOLE cycle, and this becomes non-pulsitile by the time it reaches the small arterioles.
THerefore one of the major determinants of aortic pulse pressure is compliance.
C= change V / change P
Low compliance = for every volume increase a bigger pressure increase occurs.
Why does pulse pressure increase with age
Due to lowering compliance
Systolic increases Diastolic decreases (less left over)
How does SV affect pressure
The bigger the stroke volume, the higher the systolic pressure
- preload
- afterload
- chronotropy
- inotropy
this is why Systolic pressure can increase in exercise
How can be change diastolic pressure/runoff?
TPR.
incr TPR > Less rapid runoff > inc diastolic pressure > decr PP
TPR can decrease in exercise.
What is the “pulse” you feel in arteries
PRESSURE WAVE not blood flow!!
- stretch of ascending aorta caused by LV ejection initiates a pressure wave thats propagated through the arterial system.
- Pulse (4ms) travels faster then blood itself (0.3ms)
Why does pulse pressure increase in larger conducting vessels
- decreasing compliance
- decreasing radius
- reflected wave
Ways to measure BPs
1) Palpation method (could only get systolic!)
2) Ausculatory method (both dia and sys): listen for Korotkoff sounds
No flow >(sys)> turbulent >(dias)> laminar
Above P>120
no flow = no sound
Systolic = first sound heard
120> P>80
turbulent flow= korotkoff sounds
P
laminar flow = no sound
Diastolic= last sound heard
Effect of Gravity and BP
Reference height = right atrium
Gravity does affect BP
Hydrostatic Pressure P = pgh
Rigid tubes: would have no pooling effect BUT we aren’t rigid tubes!!! So this can occur
Venous Pooling
After standing for an extended period of time.
Leads to Reduced Venous Return > postural hypertension and people faint.
What happens in renal artery stenosis?
- Reduced renal blood flow
- It thinks BF is low
- Increases blood volume (fluid retention)
- Increases arterial pressure
