I'm embarrassed to ask this.. can someone explain diastolic pressure to me?

[surfguy84]

I don't know how I don't understand this, but apparently I don't. Can someone explain what creates diastolic pressure in the heart and in circulation? What causes increases? Much appreciated.

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[chromuffin]

Diastolic pressure is the pressure that is generated while the ventricle is relaxed. What generates the pressure? Blood (volume) will expand the ventricle, creating pressure. Think about the ventricle as a closed box and you pump in some blood. It's going to increase pressure.

 

[KVBane]

You'll also notice that alot of body systems never reach zero. The lungs are never fully deflated, there is always some blood in the vasculature, deoxygenated blood always has a fair amount of oxygen anyway. So try to get in the mindset that if something in medicine exists in two states, 1 (alot) and 0 (nothing), 0 doesnt actually mean nothing, its just the lowest physiological limit.

 

[surfguy84]

Diastolic pressure is the pressure that is generated while the ventricle is relaxed. What generates the pressure? Blood (volume) will expand the ventricle, creating pressure. Think about the ventricle as a closed box and you pump in some blood. It's going to increase pressure.

Thanks for that explanation.

So then the blood pressure that is taken at your arm, is the diastolic number simply the result of the blood exerting force on the blood vessels where measurement is being taken during diastole?

 

[chromuffin]

Thanks for that explanation.

So then the blood pressure that is taken at your arm, is the diastolic number simply the result of the blood exerting force on the blood vessels where measurement is being taken during diastole?

I'm not sure what you mean. Let me just try and explain better. Diastolic number is essentially the pressure in the vasculature during the time of ventricular relaxation. Think about a theoretical leaf blower/leaf sucker combination. You can push air out or suck air in. Systole is pushing air out(blowing) and diastole is pulling air in (sucking). However, diastole doesn't cause regurgitation normally because the valves prevent back flow. You're getting a vacuum phase in diastole so that you get blood into the heart from the pulmonary vein and vena cava. The change in pressure in a blood pressure reading is a direct result of the pressure created from the "blowing" of blood out of the ventricle, into the aorta, and through the peripheral vasculature. Diastole can, like KVBane said, be thought of as the physiologic "zero"/baseline reading. Does this make sense?

 

[KVBane]

Blood pressure is given as two numbers, systolic and diastolic, and at its most simplest, systolic BP is the highest pressure experienced by arteries during the cardiac cycle (which occurs during ventricular contraction), and diastolic BP is the lowest pressure experienced by arteries during the cardiac cycle (which occurs during ventricular relaxation)

 

[Merely]

Thanks for that explanation.

So then the blood pressure that is taken at your arm, is the diastolic number simply the result of the blood exerting force on the blood vessels where measurement is being taken during diastole?

Yes I believe this is correct

 

[surfguy84]

I'm not sure what you mean. Let me just try and explain better. Diastolic number is essentially the pressure in the vasculature during the time of ventricular relaxation. Think about a theoretical leaf blower/leaf sucker combination. You can push air out or suck air in. Systole is pushing air out(blowing) and diastole is pulling air in (sucking). However, diastole doesn't cause regurgitation normally because the valves prevent back flow. You're getting a vacuum phase in diastole so that you get blood into the heart from the pulmonary vein and vena cava. The change in pressure in a blood pressure reading is a direct result of the pressure created from the "blowing" of blood out of the ventricle, into the aorta, and through the peripheral vasculature. Diastole can, like KVBane said, be thought of as the physiologic "zero"/baseline reading. Does this make sense?

Yeah, I think that makes sense. Thanks for explaining.

let me take it one step further..

So then in pulses paradoxus, you inhale and your systolic BP drops by ~10. The reason for this is because....why?

 

[KVBane]

There is a wikipedia explanation for this that goes into a significant amount of detail, so if you want you can read that. But here is a quick summary.

In normal inspiration, there is an increase in venous return to the heart which stretches the right ventricle. Normally the right ventricle expands into the area of the pericardium/lungs, and a minor change is felt. However, during cardiac tamponade (or severe COPD, asthma) pulsus paradoxicus occurs. It occurs because during inspiration, the increased stretching of the right ventricle cannot go into the pericardium, because the pericardium is filled with blood. So instead, the increased RV return pushes the interventricular septum into the left ventricle. This decreases space of the left ventricle, and causes a drop in preload (EDV). This results in a significant BP drop.