Biomedical Instrumentation Questions and Answers – Bedside Patient Monitoring System

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This set of Biomedical Instrumentation Quiz focuses on “Bedside Patient Monitoring System”.

1. A model of the normal QRS complex, called ___________
a) ECG model
b) QRS model
c) Template
d) Detection model

Explanation: A popular approach in the detection of arrhythmias is based on template matching. A model of the normal QRS complex, called a template, is derived from the ECG complex of a patient under normal circumstances.

2. Who gave the ST/AR algorithm in 1999?
a) Hewlett Packard
b) Jen and Hwang
c) Clynes
d) Cox and Nolle

Explanation: The ST/AR (ST and Arrhythmia) algorithm from Hewlett Packard (1999) is a multi lead ECG algorithm designed for both arrhythmias and ST segment monitoring.

3. In order to detect the QRS, the detection threshold is kept as ________ to prevent the detection of T waves or baseline noise as QRS complexes during a complete heart block or asystole.
a) 0.15 V
b) 0.015 mV
c) 0.015 mV
d) 0.00015 V

Explanation: In order to detect the QRS, the detection threshold is kept as 0.15 mV to prevent the detection of T waves or baseline noise as QRS complexes during a complete heart block or asystole. For optimal performance and to prevent false alarms, the lead selected for monitoring should have adequate amplitude.
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4. The contribution from each ECG lead to the QRS detection signal is proportional to its measured quality based on the waveform amplitude, and the amount of muscle and baseline noise.
a) True
b) False

Explanation: The contribution from each ECG lead to the QRS detection signal is proportional to its measured quality based on the waveform amplitude, and the amount of muscle and baseline noise. The weighting factors are updated every 200 ms to allow for a quick adaption to signal quality changes.

5. What is the value of the refractory period from the previously identified QRS complex?
a) 200 ms
b) 198 ms
c) 192 ms
d) 215 ms

Explanation: The QRs detector checks the QRS detection signal for the presence of the peak of an R wave. Search begins after an absolute refractory period from the previously identified QRS complex. The value used for the refractory period is 192 ms. This helps to prevent a T wave from being identified as an R wave.

6. The area of the P wave is ______ wide and ends ______ before the R wave peak.
a) 120 ms, 200 ms
b) 200 ms, 120 ms
c) 100 ms, 215 ms
d) 215 ms, 100 ms

Explanation: After a QRS complex is identified, a search is made on each lead independently in the area prior to the R wave to determine if there is an associated P wave. This area is 200 ms wide and ends 120 ms before the R wave peak.

7. If the height of the P wave is X, then the height of the R wave is _____
a) X/32
b) 32/X
c) X/16
d) 32X

Explanation: To be accepted as a P wave, it must be at least 1/32 of the R wave height and the P-R interval must be close to the average P-R interval.
So, P=R/32
If P=X then, X = R/32
R = 32X.

8. Which wave detection is used to differentiate between a Sinus Rhythm and a Supraventricular Rhythm?
a) P wave
b) QRS complex
c) T wave
d) R wave

Explanation: P wave detection is used to differentiate between a Sinus Rhythm and a Supraventricular Rhythm.

9. In the Beat Labeling, if the signal quality is not good, the algorithm assigns the label ______ and ______
a) Supraventricular premature, inoperative
b) Inoperative, artifact
c) Artifact, Supraventricular premature
d) Ventricular ectopic, inoperative

Explanation: Beat Labeling means that the algorithm assigns the complex one of the following labels: normal N, supraventricular premature S, ventricular ectopic V, paced P, questionable ?, and learning L. If the signal quality is not good, the algorithm assigns the label “inoperative I” and “artifact A”.

10. If a flutter or sinusoidal wave-form persists for more than __________ seconds in any ECG channel, then the monitor alarms for ventricular fibrillation.
a) 8 sec
b) 2 sec
c) 4 sec
d) 12 sec

Explanation: A separate detector continuously examines the ECG signal for ventricular fibrillation. If a flutter or sinusoidal wave-form persists for more than 4 seconds in an ECG channel, then the monitor alarms for ventricular fibrillation.

11. The heart rate is computed by averaging the most recent _________________
a) 12 P waves
b) 12 R-R intervals
c) 12 QRS complex
d) 12 R waves

Explanation: Normally, the heart rate is computed by averaging the most recent 12 R-R intervals. This average gives a stable estimate of the heart rate even when the rhythm is irregular.

12. Friesen compared _______ of nine types of QRS detection algorithms.
a) QRS complex sensitivity
b) Noise sensitivity
c) Motion artifact
d) Muscle artifact

Explanation: Friesen compared noise sensitivity of nine types of QRS detection algorithms. He established that an algorithm using a digital filter had the best performance for the composite noise corrupted data.

13. The frequency of the sinusoid and the filter leakage fraction, these two criteria are used for ____________
a) Detection of arrhythmias
b) Detection of QRS complex
c) Detection of Ventricular fibrillation
d) Detection of Heart-rate

Explanation: The detection of ventricular fibrillation is based on two criteria:
i) The frequency of the sinusoid
ii) The filter leakage fraction.

14. For an ideal sinusoid, the filter leakage fraction will be _____
a) 1
b) 0
c) Infinity
d) Undefined

Explanation: For an ideal sinusoid, the filter leakage fraction will be zero. As the ventricular fibrillation waveform is not an ideal sinusoid, a higher leakage fraction is used as the threshold for detection of this condition.

15. For how much time period, the weighting factors are updated to allow for quick adaptation to signal quality changes?
a) Every 192 ms
b) Every 16 ms
c) Every 215 ms
d) Every 200 ms

Explanation: The contribution from each ECG lead to the QRS detection signal is proportional to its measured quality based on the waveform amplitude, and the amount of muscle and baseline noise. The weighting factors are updated every 200 ms to allow for a quick adaption to signal quality changes.

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