Chapter 20- Exam 3 Flashcards
what is Q
the sum of all tissue flows and is affected by their regulation
what is the average Q in an adult
5 l/ min
what is cardiac index
Cardiac Output relative to Body Surface Area
what is the average cardiac index
3L/min/m2
what is the equation for Cardiac index
CI = CO / BSA
what is Q proportional to
tissue used of O2
look at slide
3
what happens if flow in the tissue increase
the VR increases
what is the frank starling law
that if VR increased Z shoudl increase too
what is the normal ranges for Cardiac index
2.6-4.2 L/min/m2
when will there be cardiogenic shock in relation to CI
less than 2.2 L /min/m2
what does right atrial pressure represent
venous return
what happens when RAP increases
it represents more blood flowing into right atria
why does a platue happen in the Q curve graph
this is showing how the heart limits Q as it can not longer fill anymore
what is hypereffective heart
this increase Q above normal
what are two factors that can make the heart a better pump than normal
1 SNS stimulation
2 hypertrophy of the heart
what is hypoeffective heart
this is a decrease in Q form the normal
– Or anything that decrease the hearts ability to pump the blood
what are some things that decrease the hearts ability to pump
- Increased arterial pressure against which the heart must pump, such as in hypertension
- Inhibition of nervous excitation of the heart
- Pathological factors that cause abnormal heart rhythm or rate of heartbeat
- Coronary artery blockage, causing a “heart attack”
- Valvular heart disease
- Congenital heart disease
- Myocarditis, an inflammation of the heart muscle
- Cardiac hypoxia
what is one way you can effect Q
is by changing the external pressure on the outside of the heart
what is intraplueral pressure
= pressure in the chest cavity) is an external pressure on the heart
what is the typical intraplueral pressure
about -4 mmHg
what happens with and increase in intraplueral pressure
Increase IPP from -4 to -2mmHg shifts Q curve to right
what must happen to fill chambers
Must increase RAP to fill chambers to overcome the external pressure
what is Cardiac tamponade
fluid accumulation between the heart and the pericardium that compresses the heart
what are some factors that can alter external pressure and shift the Q curve
- Cyclical changes of intrapleural pressure during respiration
- Breathing against a negative pressure
- Positive pressure breathing
- Opening the thoracic cage
- Cardiac tamponade
what are the pressure of VR
- right atrial pressures (RAP)
- Central Venous Pressure (CVP)
what is RAP
–Pressure in Right Atrium
–Reflects venous return
–Influences/determines preload
–~ = 0 mmHg
What is CVP
–Pressure in the venae cavae near the Right atrium –Approximates RAP –CVP and RAP often different –Influences/determines preload –~ = 2 to 6 or 3 to 8 mmHg
what are 3 principles that influence the VR curve
1.Right Atrial Pressure
2.Mean Systemic Filling Pressure Next
• Forces blood toward the heart
3.Resistance to blood flow
what is the mean systemic filling pressure
Both the arterial and the venous pressures equilibrate when all flow in the systemic circulation ceases at a pressure of 7 mm Hg
what happens to VR when RAP increases
it will decrease
when will mean systemic filling pressure be relavent
if the heart pumping is compromised causing right atrial pressure to rise
what happens to VR when RAP is 7 mmHG
it will fall to 0
what happens when VR = 0 mmHg
cardiac pumping = 0
what is the VR equation
VR = Psf - PRA
—————–
RVR
what is Psf
Systemic Filling Pressure
what is PRA
Right Atrial Pressure
what is RVR
Resistance to Venous Return
what is normal Psf
7mmHg
what is normal PRA
0mmHg
what is normal RVR
1.4 mmHg/ L*MIn^-1
when does the VR curve Plateaus at
-2 mmHg
when does the plateau of the VR occur
even when right atrial pressure falls to −20 mm Hg, −50 mm Hg, or
what is the platueau caused by
This plateau is caused by collapse of the veins entering the chest.
what happens with the great the volume of blood of the circulation
the greater is the mean circulatory filling pressure
what happens 4000 ml blood
what happens at normal blood volume of 5 L
MCFP is ~7mmHg Purple Line
If Blood Volume Increases, MCFP Increases Orange Line
look at slide 18
what happens with sns stimulation of the blood
smaller container,
At normal blood volume, MCFP Increases Green Line
(look at slide 18)
what happens with PNS stimulaiton
larger container
look at slide 18
what happens with higher MSFP
VR curve shifts upward and to the right.
look at slide 19
what happens with lower MSFP
VR curve shifts downward and to the left
look at slide 19
what is an equation for VR (another one )
VR = CVP – RAP
look at slide 19
what happens with the resistance in the veins increase
blood is less able to move out of v( look at slide 20)eins
why is it so hard for the venous pressure to rise
Because veins are highly distensible venous pressure rises very little
( look at slide 20)
what happens with the RAP rises to the MSFP
VR =0
look at slide 20
to complete ciruclation what needs to work together to make this happen
the heart and the systemic circulation must operate together.
what must happen with the heart and the systemic circulation to complete circulation
(1) the venous return from the systemic circulation must equal the cardiac output from the heart
(2) the right atrial pressure is the same for both the heart and the systemic circulation
look at slide
23, 24
what happens if the Q does NOT = VR
then all blood would either accumulate or be removed from the chest
what happens if left ventricle output is 6 and venous return = 5
all blood would be shifted to the periphery.
how do you measure Q
- Electromagnetic flowmeter
- Indicator dilution (dye such as cardiogreen)
- Thermal dilution
- Oxygen Fick Method
what is the Oxygen Fick Method equation
O2 consumption = Q x (A-V O2 difference)
look at slide
28 at the equation written out
