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Principles I Test 4

Invasive Blood Pressure Monitoring

QuestionAnswer
What are the indications for invasive blood pressure monitoring? need for real-time continuous pressure monitoring, cuff measurement is unreliable, waveform diagnostics desired, repeated blood sampling needed
What are some potential complications of invasive blood pressure monitoring? ischemia distal to site, hematoma-compartment syndrome, arterial trauma, infection, thrombus formation, vasospasm, bleeding, fistula, air embolus, heparin overdose (rare-only if flush bag contains heparin)
What is the most important determinant of LV after load? blood pressure
Automated non-invasive blood pressure monitoring is based on __________ oscillometry (measuring vibrations)
What are the components of an invasive blood pressure monitoring system? catheter, tubing, stopcocks, extension tubing, transducers/diaphragms, flushing devices, amplifiers, cable connections, electronic filters
What does the transducer do? it takes the mechanical signal and converts it into an electrical signal (what we see on our monitors)
What is dynamic response? physical behavior of a system; it is characterized by elasticity, mass & friction; it is characterized & assessed by natural frequency and damping coefficient
What is hertz (Hz)? a unit for measuring frequency; number of cycles per second; 1 cycles per second = 1 Hz
What is oscillation? back and forth repeated motion
What is harmonics? stretch and recoil of a spring; a series of oscillations in which each oscillation has a frequency that is an integral multiple of the same basic frequency; this is an abnormal occurrence.
What is resonance? exaggerated wave amplitudes occurring when the monitored frequency matches the system's nature; frequency resulting in overshoot or overestimated wave reading (when harmonics occur the system is resonate)
What is natural frequency? how easily or rapidly the system oscillates; all objects have a natural frequency at which they optimally vibrate when disturbed or struck
How is frequency measured? in Hertz (Hz) {cycles per second}
The higher the natural frequency, the more ______ and _________ the signal quality with less distortion. precise and accurate
Natural frequency should be at least ________ the frequency of the waveforms to be monitored. 5 times
If the patient's heart rate to be monitored goes as high as 180, how many Hz are needed in the system? 15 Hz (HR = 180, which is 3 Hz; 3 x 5 = 15 Hz)
What is the damping coefficient? numerical indicator of the degree of damping
What is damping? defines an object's tendency to cease vibrating/oscillating
Completely undamped system means a coefficient of what? What are the implications of this? 0; object will likely continue to vibrate indefinitely
Completely damped system means a coefficient of what? What are the implications of this? 1.0; object will instantly return to baseline resting state as soon as stimulus withdrawn
What is critical damping? What is the coefficient for this? when one displacement causes one vibration; coefficient is 0.4
How does an under-damped system skew blood pressure readings? SBP too high, DBP too low; MAP will be accurate; sharp and exaggerated waveform
How does an over-damped system skew blood pressure readings? SBP too low, DBP too high; MAP will be accurate; wave form is smooth with no dicrotic notch
What does the dicrotic notch represent on an arterial waveform? closing of the aortic valve
What is the lowest damping coefficient number that will provide accurate results? 0.4
What is the ideal damping coefficient? 0.6 - 0.7
What is the best method of calculating the dynamic response of an arterial blood pressure monitoring system? square wave test
How do you perform the square wave test? flush artline to make "square wave"; once done flushing observe number of oscillations before returning to baseline
How many oscillations are present before returning to baseline during the square wave test in an optimally damped system? 1.5 - 2 oscillations before returning to baseline
How many oscillations on the square wave test represent an underdamped system? > 2 oscillations before returning to baseline
How many oscillations on the square wave test represent an over damped system? < 1 oscillation before returning to baseline
What is the optimal tubing length for an arterial blood pressure monitoring system? 4 feet
Which system is easier to deal with...an underdamped system or an over damped system? underdamped....because you can always add something to the system to dampen it more
Dynamic response issues affect ______ the most and _____ the least. Therefore, ______ is the most accurate reading, SBP, MAP, MAP = most accurate reading
The properties of the system control __________, but the clinician can control the ___________. natural frequency; damping
Decreased damping and natural frequency augments the wave and introduces _________ into the system. resonance
Natural frequency should be as high as possible, greater than _____. 7.5 Hz
Zeroing means you are taking the art line from ________ pressure to _________ pressure. atmospheric; gauge
Where should the transducer be leveled? 5 cm below sternal border at the 4th intercostal space corresponds with the aortic root
1 cm of height is equal to.... 0.75 mmHg
The level of the auditory meatus or tragus of the ear is equal to the _____________ and estimates _____. Circle of Willis; CPP
Raising the patient about the level of the transducer will produce _______ pressure readings higher
Lowering the patient below the level of the transducer will produce ________ pressure readings lower
How does aortic stenosis change the arterial pressure waveform? delayed upstroke, narrowed pulse pressure
How does aortic regurgitation change the arterial pressure waveform? sharp rise, double peak
How does hypertrophic cardiomyopathy change the arterial pressure waveform? spike and dome due to midsystolic obstruction
True or false: compliance of the vessel affects flow true; older patients have less compliance
Created by: Mary Beth