Ch 6 - 8 Pressure Monitoring Systems Flashcards
Fluid-Filled Monitoring Systems
• Physical Principle: A change in pressure at any point in an unobstructed _____________ results in a _______________ at all other points of a system •
Fluid Filled System
Similar Pressure Change
Fluid medium is not very ____ accurate _______ of pressure
Compressible
Transmission
Guide wire > Introducer > vessel
> removal of introducer > Insertion of dilator/sheath > removal of dilator > Sheath advanced.
Fluid-filled Monitoring Components
- On site Catheter
- LOW Compliance pressure tubing.
- Transducer
- Amplifier / Monitor
- Auto-flush System
Name the procedure whereby the pressure transducer and tip on the on site vascular catheter are on the same plane
Leveling
Reference points for leveling ?
Heart Level / Tricuspid / Mid-chest
The effects of differences in transducer/midchest position on hemodynamic monitoring Principle: Liquid has a ___?
Weight
pressure exerted on the transducer diaphram by the weight of fluid within the monitoring tubing.
Hydrostatic Pressure
For every 1” the transducer is BELOW mid-chest level, the weight of the fluid on the transducer diaphragm will add how many mmHg?
2 mmHg ABOVE the true intravascular or intra-cardiac pressure.
For every 1” the transducer is ABOVE mid-chest level, the weight of the fluid on the transducer diaphragm will add how many mmHg?
2 mmHg below the true intravascular or intra-cardiac pressure.
Zero Referencing is Used to eliminate the effect of ?
Atmospheric Pressure
A reliable monitoring system should be as simple as possible.
Monitoring catheter bore size? Connecting tubing ? Tubing Connectors? Pressure bag ? System must be free of ? No patient moving
> 18 gaugue or 7 Fr
Low Compliance
Overdamping waveform distortion :
(Exaggerated response)
Caused by tubing connections that are too compliant or too long
Underdamping waveform distortion :
(Blunted response)
Caused by air bubble in the circuit, partial obstruction of catheter or tubing that is too compliant or too long.
Appropriate length for tubing in fluid filled monitoring systems?
< 3 - 4 ft
Fluid-filled monitoring systems:.
4 SYSTEM related variables ?
- ) Pressure transducer + - H2O
- ) Air bubbles in system
- ) Compliance of tubing
- ) Catheter lumen size
Fluid-filled monitoring systems:
2 Patient -Related Variables ?
1.) hyperdynaminc due to sepsis,
AI, or stress.
2.) Tachycardia
loss of energy and vibrations within the monitoring system due to frictional resistance to movement of the pressure signal and absorption of the pulsatile energy.
Damping
Movement of the catheter tip in the circulation in response to pulsatile flow.
Catheter whip (fling)
The introduction of a selected pressure to the amp/ monitor of transducer to verify faithful reporduction of the pressure signal
Calibration
false signal superimposed on the true signal
Artifact (noise
The monitoring system’s ability to measure physiologic pressure changes, Dynamic response relates to the natural frequency & damping characteristics of the system.
Dynamic response
pressure produced by fluid in motion
Hydrodynamic pressure
pressure exerted by a stationary fluid column.
Hydrostatic pressure
the frequency at which a in-situ catheter and monitoring plumbing vibrate when stimulated. Hz Tuning fork effect
Natural frequency
monitoring system vibration that occurs when the patient’s pressure wave contains a component frequency equal to the monitoring systems natural frequency. Upstroke & downstroke exaggerated (spiked).
Overshoot/undershoot
performed to eliminate effects of atmosphere and hydrostatic pressure from measured physiologic reading.
Zeroing
Troubleshooting a No Waveform situation?
- Power
- Scale
- Stopcocks
Troubleshooting Artifact ?
- Interference
- Movement
Troubleshooting Waveform Drifting ?
- Temperateure Change
- Kinked cable
Troubleshooting Unable to flush situation ?
- Stopcock
- pressure bag
Troubleshooting High Readings?
- Cailbration
- level
- flush
Troubleshooting Low Readings ?
- Level
- loose connections
Troubleshooting Overdamped waveforms ?
- Air bubbles
- kinks
- thrombus
- position
Blood pressure is a measure of force as it is exerted on the _________ by the blood.
Arterial Walls
BP results from ?
The pressure generated by the beating heart and the resistance to blood flow by the arteries.
100 - 130
————-
60 - 90
Blood pressure monitoring is an essential ________________ tool.
Assessment
During CPB, the perfusionist constantly montiors ABP and will keep the MAP in the range of what ?
60-70 mmHg (adult)
Name the average driving force for movement of blood in the arterial system throughout the cardiac cycle. It is the same in all parts of the cardiovascular system when the patient is supine.
(MAP)
Indirect measurement of Arterial Blood Pressure ?
- Auscultation
- Korotkoff sounds =
stethoscope is placed over
the brachial artery - Palpataion
- Automatic Doppler
Direct measurement of Arterial Blood Pressure ?
- Occlusion techniques
- Intra-arterial line
Step # 1 in the Arterial trace?
Aortic Valve Opens
Step # 2 in the Arterial trace?
Pressure Increases as blood flows into the Aorta. AKA Anacrotic Rise (Inotropic Component)
Step # 3 in the Arterial trace?
Maximum Pressure (Systolic)
Step # 4 in the Arterial trace?
Aortic Valve closes
AKA
Dicrotic notch
Step # 5 in the Arterial trace?
Pressure Falls
as blood flows out of the Aorta
Step # 6 in the Arterial trace?
Minimum Pressure (Diastolic)
6 steps in the Arterial Trace?
AV opens Pressure increases Max Pressure (Systolic) AV closes Pressure falls Min Pressure (Diastolic)
Anacrotic Rise
(inotropic Component) =
Pressure Increase as blood flows into the Aorta.
Dicrotic notch =
AV valve closes
Pulse Pressure
(Systolic - Diastolic) = 40 mmHg
MAP equation ?
3
As the pressure falls, the Aortic valve closes; signaling what?
Onset of diastole
2 Arterial traces that show: 110/80 and 120/80. Which one indicates a pressure recorded in the Aorta ?
Which indicates pressures recoded in the radial artery?
110/80 = Aorta 120/80 = Radial
(* Capture)Pulse pressure increases with
- distance from the heart.
* The mean pressure does not change, therefore there is no loss of energy.*
What cause Pulse pressure to increases the further away from the heart?
Caused by reflected pressure waves bouncing off the walls of the aorta.
What are some conditions that affect Arterial Pressure Waveform Morphology ?
- Arrhythmias
- Hypertension/hypotension
- Aging
- Post-op surgery
- Hypovolemia
- Vasoconstriction
- Normal LV
Aging affects Arterial Pressure Waveform Morphology by ?
Loss of COMPLIANCE of peripheral vessels.
7 Hazards of indwelling arterial catheters ?
- ) Ebololus
- ) Thrombis
- ) Tissue Ischemia
- ) Infection
- ) Hemorrhage
- ) Accidental Drug Injection
- ) Volume Overload
