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Principles I Test 4
Invasive Blood Pressure Monitoring
| Question | Answer |
|---|---|
| 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
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