Module 3 - Blood pressure measurements Flashcards
Describe the physics behind blood pressure behavior
at the end of the diastolic phase the first atrial contraction occurs. The p-wave ensures that contraction will take place and this contraction will of course increase the volume in the ventricles and increase the pressure a bit.
then the QRS complex occurs and the ventricles contract. Lead to a vast pressure build up until the aortic valve opens. Ejection takes place at peak pressure. Ventricles will relax, pressure drops, flow starts coming in. The aortic valve will close
DRAW TAB
draw the waveform of the bloodpressure curve
start 80 with diastolic in mmHg
peak at 120 systolic pressure in mmHg
Where does the dichrotic notch come from?
It is a dip in the blood pressure curve. Happens right before the aortic valve closes. Then there is some backward flow as the ventricles relax
There are two ways in which the cardiac output can be adjusted. .. talking about two specific control mechanisms. Name these and explain what they do
Vasodilation
- if tissue needs more blood, then more blood needs to flow, then more atrial filling is needed, thus heart muscles need to strectch more so that the force of contraction increases. This increases the pumping effectiveness
Baroreceptor reflex
- if blood pressure droops, information gets sent to brain, HR is adjusted so that blood pressure can increase again
Identify how arteriosclerosis, aortic valve stenosis and patent ductus arteriosus affect the blood pressure behavior (and curve)
TAB DRAWING
- arteriosclerosis -> stiff vessels -> leas to higher pressure buildup, from 120 to 160
- aortic valve stenosis -> no fast pressure buildup -> no dichrotic notch
- patent ductus arteriosis -> aortic valve does not close fully, blood flows into pulmonary artery, low diastolic pressure (40 ipv 60)
Name three ways to measure blood pressure
- Manual non-invasive measure
- Automatic non-invasive measure
- Invasive arterial blood pressure
How does non-invasive manual blood pressure measurement work?
Uses pressure management cuff and stethoscope.
Inflate cuff completely around the arm, so that pressure is higher then systolic pressure. First sound when blood starts flowing is the systolic pressure.. Reach diastolic when the last sound is heard.
How does automatic non-invasive blood pressure measurement work?
Also inflatable cuff, however automatic listening.
If there is no opening of the vessel there is random vibration. As soon as the cuff deflates, max blood pressure. Mean arterial pressure is when lowest cuff pressure with largest oscillation.
The more the cuff opens the more oscillation. Diastolic is estimated
How does invasive blood pressure measurement work?
A catheter is inserted in the artery, then there is a fluid canal that leads towards the pressure measurement system, and a fluid reservoir.
Pressure wave from blood is transported via the fluid filled system to the pressure management system.. Transducer needs to be at the same height as the heart
DRAW TAB
Draw three ways of blood pressure measurement
2x non invasive, automatic, manual
1x invasive
Name limitations of various blood pressure management
- Non-invasive manual
- Inappropriate cuff size leads to errors
- Depends on hearing acuity of physician
- Accuracy is limited
- Too fast deflating is bad
- not continuous
- non-invasive automatic methods
- same as above
- sensitive to movement artefacts since it measures oscillations
- diastolic is estimated quantity
- systolic is hard to detect, no difference almost with respect to noise
- not continuous
- invasive blood pressure
- most erros from incorrect nulling
- is continuous however
- catheter errors
- catheter move
- air bubble
- air bubble
- microtip transducer
- additional tube for blood samples needed
- too expensive
