lecture 8 hemodynamics part 1 student
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8/4/2019 Lecture 8 HEmodynamics Part 1 Student
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Hemodynamics Part 1
Pressures
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Hemodynamics
Study of the movement of blood and itsrelationship with:
Cardiac function Pulmonary and systemic blood pressures Resistance throughout the entire
Cardiovascular system
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Lungs
Brain
Liver
Stomach
Pancreas
Intestines
Kidneys
Skin
Muscle
Arterioles
Pre-capillarySphincters
Veins(Flexible Compliant Pipes)
Arteries(Stiff Inflexible Pipes)
Circulation:
Blood flow fromhigh to low pressure(remind you of anything?)
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RA
RV
LUNGS LA
LV
AORTA
ARTERIOLES
SYSTEMICARTERIES
VEINS
(90)
(40)
low compliance
13% of blood volume
high compliance64% of blood volume
(2)
CAPILLARYBEDS
7% of blood volume
9% of blood volume
(7)
(13) (3)
Flow (Q) = upstream pressure downstream pressure
resistance
The CardiovascularHemodynamic System
Mean pressures in red
(20)
(8)
204
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Pressures we can measure
Arterial Blood Pressure
Central Venous Pressure
Pulmonary Artery Pressure
Left Atrial Pressure
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Arterial Blood Pressure
Pressure = Flow x Resistance Flow = how fast stroke volume exits heart Resistance =diameter of vessels (SVR)
Measurements can be Non-invasive
Invasive with indwelling catheter
Normal Values:
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Waveform from A-line
Ejection
If unable to see dicrotic notch may be dampened, pressure may be falsely low
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Arterial Pressure cont
Pulse Pressure Difference between Systolic and Diastolic
pressure NORMAL = 30-40
Depends on SV and arterial compliance Low SV = decreased pulse pressure
Mean Airway Pressure Average pressure NORMAL = 80-100mmHg
MAP = Systolic + (2 * Diastolic)
3
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Central Venous Pressure (CVP)
A Catheter is placed with the tip lying in theSuperior vena cava or Right Atrium
Measures mean Right Atrial Pressure (RAP)
Indications:
To assess circulatingblood volume and guide
fluid replacement
Other Benefits: blood draw &
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Factors affecting CVP
Blood Volume status Volume must be enough to fill vascular space If right heart pump is OK, CVP reflects
vascular volume
Heart capabilities how well can it pump?
Venous tone (which changes vascularResistance and space)
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RVLV
LUN
GS
Tissue
RA LA
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RVLV
LUN
GS
Tissue
RA LA
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CVP will Increase with: Fluid overload Right heart failure- Severe left heart failure- Large Pulmonary Emboli- Pulmonary hypertension PEEP - how much?
CVP will Decrease with:
Hypovolemia (dehydration, Blood loss) Vasodilation (Shock)
RV LV
LUNGS
Tissue
R
A
LA
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CVP waveform
Atrial
contr
action
Clo
sure
ofA
V
Valve V
entric
ular
systole
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CVP
Complications: Pneumothorax, bleeding, infection, thrombus,
air embolus
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PA Catheter
Balloon tipped catheter placed with the tiplying in the Pulmonary Artery
Can obtain both right and left heart pressures Used for CO determination Can obtain Mixed Venous samples Some have SvO2 and pacing capabilities
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Balloon Port
Proximal Port
Distal Port
Thermister
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Distal Port
Measures:
Proximal Port
Measures:
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Pressures obtainable: CVP (RAP) PA (Systolic, diastolic and mean) PCWP (PAOP) This reflects Left heart fuiinction
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PA Catheter Placementand Waveforms
(CVP)
CVP
2-6
RV
20-30
PAP20-306-15
PCWP4-12
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Pulmonary Artery Pressure
This is the Pulmonary BP Systole pressure depends on:
Stroke volume, rate of blood flow (force of contraction), andresistance of pulmonary vasculature
The mean PAP is the average pressure in the pulmonary system Its used to help determine Pulmonary Vascular Resistance (PVR)
and is used to assess how much work the R ventricle must pushagainst (Afterload)
Normal value is: 20-306-15
Mean : 10-20mmHg
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Indications Hemodynamically unstable patients Cardiogenic shock, sepsis Unstable thoracic surgery patients
Complications Same as CVP but with the additional:
Dys-rhythmia (mostly during placement) Pulmonary infarct if it wedged in PA
Pulmonary Artery PressureMeasurement
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Pulmonary Artery Pressure
PA Pressures will Increase with: Increased Pulmonary resistance
PE, pulm hypertension, COPD (cor pulmonale)
Increased contractility of heart PEEP how much?
PA pressures will Decrease with: Decreased resistance Decreased Stroke volume
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Pulmonary Capillary Wedge Pressure(PCWP, PAOP, Wedge)
Represents mean Left Atrial Pressure (LAP) Indicates Left ventricular function
With the balloon inflated, the wedged PACcreates a channel with no blood flow from thecatheter tip to the left atrium, thus allowingindirect measurement of the leftatrial pressure.
Normal:
2-12 mmHg
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Preload -Ventricular end diastolic volume / Pressure - the amount of stretch ofventricle
RV preload indicator is =____________(pressure)
LV preload indicator is = ____________ (pressure)
Afterload - resistance to ventricular emptying during systole or
the amount of pressure the left ventricle must generate to squeeze blood into theaorta.RV afterload = ____________ (Pressure)LV afterload = _____________(Pressure)
Definitions
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Starlings Law of the Heart and Contractility
SV
(left ventricularperformance)
Preload
(venous return or EDV)
ucontractility
normalcontractility
d contractility(heart failure)
Preload X
SV at Preload X - u contractility
SV at Preload X - N contractility
SV at Preload X - d contractility
Starlings Law:The greater the EDV (preload), the more blood comes out of the heart until
State of Myocardial Contractility:Determines the amount of blood(SV) that comes out of the heart at agiven preload
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SVR and PVR
Resistance - the sum of all forces that opposeblood flowdue to:
Length of vasculature (L) Blood viscosity (V) Vessel radius (r)
Systemic Vascular Resistance (SVR):
(MAP RAP) * 80 / CO
Pulmonary Vascular Resistance (PVR)(Mean PAP LAP) * 80 / CO
The largest variable is Vessel RADIUS
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Similarities
How do you calculate Resistance on aventilator?
Change in airway pressure / flow
Same thing here: change in vascular pressure / CO (flow)
The Cardiovascular
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RA
RV
LUNGS LA
LV
AORTA
ARTERIOLES
SYSTEMICARTERIES
VEINS
(90)
low compliance
13% of blood volume
high compliance64% of blood volume
(2)
CAPILLARYBEDS
7% of blood volume
9% of blood volume
(13) (3)
Flow (Q) = upstream pressure downstream pressure
resistance
The CardiovascularHemodynamic System
Mean pressures in red
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SVR
(95-5)mmHg*80 /5L
=1440 dyne-sec/cm5
Normal = 800-1200
(15-5)mmHg*80 / 5
=160 dyne-sec/cm5
Normal =
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End Diastolic Volume (EDV)
Volume at the end of diastole(end of ventricular filling). In ahealthy heart this is directlyproportional to venous return
Stroke Volume (SV) = CO / HR
Ejection Fraction (EF) = SVEDV
Ventricular Volumes - Definitions
SystoleED
V
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Homework state whether the pressures in eachwill go up, down or stay the same.
CVP PAP PCWP
Normal =
Right ventricular failure
Left ventricular failure
Pulmonary hypertension
Non-cardiogenic pulmonaryedema (ARDS)
Mitral valve stenosis orinsufficiency
Pulmonary Embolism