Integrative physiology Cardiovascular homeostasis Flashcards
What is arterial blood pressure?
Arterial blood pressure is the driving force that maintains blood flow through the capillary beds of the body
How do we calculate cardiac output?
Heart rate x Stroke volume
CO = HR x SV
How do we calculate Strove volume?
EDV - ESV
How do you calculate the Velocity of blood flow?
V = Q / A
V = Velocity of blood flow (cm/sec)
Q = Volume Flow (ml/sec)
A = Cross-Sectional Area (cm^2)
Calculate the Velocity at point X and Point Y
Does the blood closer to the centre of the vessel move faster, or the blood clossest to the wall of the vessell?
The centre. As blood flows through a vessel, the blood nearest the wall of the vessel moves more slowly than the blood in the centre of the vessel
What is systolic blood pressure?
Systolic blood pressure is a measure of the force exerted by the ventricles of the heart.
What is diastolic blood pressure?
Diastololic blood pressure is a measure of the force exerted by the blood upon arterial walls when the ventricles are relaxed.
How do we express blood pressure?
Systolic pressure / Diastolic pressure
What is the average BP for Men and Women?
Men = 120/80
Women = 110/70
In general does SBP and DBP increase or decrease with age, physical size, and excersize?
Increase
What is the physiology behind a pulsation?
Each pulsation is caused by a pressure wave travelling down the arteries following the expulsion of blood from the heart during systole. Pressure wave causes expansion of the walls as it travels and this can be detected as a pulse.
What do we use to indirectly measure Arterial blood pressure?
SBP and DBP can be measured indirectly in humans using a sphygmomanometer.
How does a sphygmomanometer work?
Cuff placed around arm over brachial artery, Inflated with air to a pressure greater than SBP. The pressure on the arm causes collapse of the artery underneath preventing blood flow to lower arm. BP can then be measured by detecting changes in blood flow in the artery at a point distal to the cuff as pressure is lowered.
What is pulse pressure?
Pulse pressure is the numerical difference between SBP and DBP. Normally about 40mmHg.
How do we measure blood pressure by Auscultation?
- Have subject sit with arm/elbow straight
- Wrap cuff firmly around brachial artery about 2.5cm above elbow with cuff being level to heart making sure you can read manometre but subject cannot.
- Place stethoscope diaphragm (closed) over brachial artery just below cuff
- Inflate to about 140-150mmHg then release pressure slowly whilst listening with stethoscope. Record pressure where a regular tapping is first heard. Record this as SBP.
- Continue lowering the pressure until you hear a muffled sound this is phase 4 DBP. Keep lowering until muffled sound dissapears, This is phase 5 DBP.
- Pnce sounds have ceased deflate cuff and allow subject to rest for atlease 1 min. Repeat procedure until consistent reading are obtained (no variation beyond 5%)
What is happening physiologically during the measurement of the SBP?
Arterial blood pressure just exceeds the cuff pressure during systole and the blood spurts through the partially occulded artery causing turbulence and vibration.
What is the Doppler Flowmeter? What is its biggest restriction?
The doppler flowmeter enables blood flow to be measured from the surface of difficult to measure regions. (This is a qualitative method). It shows changes in velocity well.
The biggest restriction is that it can only measure SBP as it can only detect when blood flow resumes after the cuff is deflated.
What is the difference between the “reading” from the doppler flowmeter and the stethoscope?
Doppler flowmeter: Detects the pressure wave
Stethoscope: Can only hear turbulence caused by inflation of the cuff
What happens during the use of the doppler flowmetre?
The principle of operation is known as the doppler effect. Ultrasound energy at freq 10MHz is directed onto the moving blood stream. A portion of the transmitted energy is reflected back from the blood cells.
Blood movement = Frequency Shift
Height of Curve is proportional to velocity.
How do we calculate MAP?
MAP = CO x TPR
or
MAP = 1/3 x SBP + 2/3 x DBP
Calculate MAP: Subject has a SBP of 115mmHg and a DBP of 75mmHg?
(115/3) x 1
+
(75/3) x 2
= 88.3
therefor MAP = 88mg
What is the Schneider Test?
Test of circulatory efficiency; A test of Cardiovascular fitness rather than a measure of athletic condition. BP and Pulse Rate will be measured.
What does the term distended mean in regards to veins?
Englarged or stretched out due to internal pressure.
What is the Valsalva Manoeuvre?
The forced expiration made against a closed glottis (basically pinching your nose and closing your mouth) to increase intra-thoracic pressure, preventing venous blood flow entering the thorax causing venous distention in areas such as the jugular vein.
Valsalva Manoeuvre = Decrease intra-thoracic pressure and increase in venous distention/pressure
Used to balance pressure in ears
Can you measure venous pressure with the sphygmomanometre? explain
No, because venous blood pressures are so much lower than arterial pressures. We can only estimate venous pressures based off of calculations that produce estimates at best.
How can we “calculate” venous pressure (Pv)?
Through the following procedure:
- Line subject up next to whiteboard and mark height of right atrium
- Ask subject to extend arm carefully observing dorsal veins of hand
- when veins collaps mark height on whiteboard and draw a vertical plane
- record vertical distance between mark of atrium and vertical plane
