Q.1 What is the fundamental principle behind a pulse oximeter?
It measures arterial pressure directly
It uses two wavelengths of light to calculate oxygen saturation
It records electrical activity of the heart
It uses ultrasound to detect blood flow
Explanation - Pulse oximeters shine red (≈660 nm) and infrared (≈940 nm) light through a tissue, and by comparing the absorption at both wavelengths they estimate arterial oxygen saturation.
Correct answer is: It uses two wavelengths of light to calculate oxygen saturation
Q.2 Which tissue property primarily influences the absorption of light at 660 nm used in pulse oximetry?
Hemoglobin concentration
Nerve conduction velocity
Skin thickness
Blood viscosity
Explanation - Red light (660 nm) is absorbed strongly by oxyhemoglobin; the amount of absorption changes with hemoglobin concentration, allowing calculation of saturation.
Correct answer is: Hemoglobin concentration
Q.3 What is the typical measurement range for SpO₂ in a healthy adult?
50–70 %
70–90 %
80–100 %
90–100 %
Explanation - Normal arterial oxygen saturation in healthy adults ranges from 95–100 %; devices often display 90–100 % as the normal clinical range.
Correct answer is: 90–100 %
Q.4 Which of the following factors can cause a pulse oximeter reading to be falsely low?
High ambient light
Cold extremities
High hematocrit
Low ambient temperature
Explanation - Peripheral vasoconstriction in cold hands reduces blood flow and pulse signal amplitude, often leading to falsely low SpO₂ readings.
Correct answer is: Cold extremities
Q.5 What does the term 'pulse wave amplitude' refer to in photoplethysmography?
The peak-to-peak voltage of the arterial waveform
The DC component of the light absorption signal
The heart rate in beats per minute
The baseline skin reflectance
Explanation - In PPG, the pulsatile component represents changes in blood volume with each beat, measured as peak-to-peak amplitude.
Correct answer is: The peak-to-peak voltage of the arterial waveform
Q.6 Which technique uses the Doppler shift of ultrasound waves to measure blood flow velocity?
Thermodilution
Laser Doppler
Spectral Doppler ultrasound
Capacitance plethysmography
Explanation - Spectral Doppler measures frequency shift of reflected ultrasound, allowing calculation of velocity profile across the vessel.
Correct answer is: Spectral Doppler ultrasound
Q.7 In laser Doppler flowmetry, the detected signal is proportional to:
The square of the blood flow velocity
The concentration of red blood cells
The number of moving scatterers within the tissue
The optical density of the tissue
Explanation - Laser Doppler measures the frequency shift from moving red blood cells; the power of the signal correlates with the count of moving scatterers.
Correct answer is: The number of moving scatterers within the tissue
Q.8 Which of the following is NOT a common source of motion artifact in photoplethysmography?
Patient movement
Vibrational noise from equipment
Ambient light interference
Electrical interference from other sensors
Explanation - While electrical noise can affect sensors, motion artifacts primarily arise from patient motion, mechanical vibrations, and ambient light changes.
Correct answer is: Electrical interference from other sensors
Q.9 What is the physiological basis for the use of two wavelengths in pulse oximetry?
Different wavelengths penetrate to different depths
Oxy- and deoxyhemoglobin have distinct absorption spectra
Wavelengths are chosen to avoid interference from skin melanin
It allows measurement of both heart rate and blood pressure
Explanation - The key is that oxy- and deoxyhemoglobin absorb light differently at 660 nm vs. 940 nm, enabling calculation of saturation.
Correct answer is: Oxy- and deoxyhemoglobin have distinct absorption spectra
Q.10 Which parameter is directly measured by a Doppler ultrasound probe in the assessment of arterial blood flow?
Pressure gradient
Flow velocity
Blood volume
Oxygen saturation
Explanation - Doppler ultrasound measures the frequency shift caused by moving blood cells, which can be converted to velocity.
Correct answer is: Flow velocity
Q.11 The term 'perfusion index' in pulse oximetry refers to:
Ratio of arterial to venous blood flow
Amplitude of pulsatile signal divided by the total signal
Heart rate divided by SpO₂
Skin temperature relative to core temperature
Explanation - Perfusion index is the ratio of the pulsatile component to the non-pulsatile component of the light absorption signal, indicating peripheral perfusion.
Correct answer is: Amplitude of pulsatile signal divided by the total signal
Q.12 Which of the following is a limitation of thermodilution for measuring cardiac output?
Invasiveness
High cost
Inaccuracy in low cardiac output states
Requires large blood volume for dilution
Explanation - Thermodilution can be less accurate when cardiac output is very low, as the temperature change is small and measurement noise increases.
Correct answer is: Inaccuracy in low cardiac output states
Q.13 In the context of blood flow measurement, what does 'velocity profile' describe?
How velocity changes over time during a heartbeat
The distribution of flow velocity across the vessel cross‑section
The relationship between speed and pressure
The average speed over a cardiac cycle
Explanation - The velocity profile shows how fast blood moves at different radial positions within a vessel; laminar flow shows a parabolic profile.
Correct answer is: The distribution of flow velocity across the vessel cross‑section
Q.14 What is the most common placement for a fingertip pulse oximeter in clinical practice?
Nail bed of the middle finger
Earlobe
Toe
Finger of the hand
Explanation - Finger tips, especially the middle or index finger, provide good optical access and are widely used for pulse oximetry.
Correct answer is: Finger of the hand
Q.15 Which of the following best describes the 'DC component' in a PPG signal?
The pulsatile part related to heartbeats
The baseline light absorption due to static tissues and blood
The noise from ambient light
The signal from capillary refill
Explanation - The DC component reflects constant light absorption by tissue, skin, and static blood; it is subtracted to isolate the AC pulsatile signal.
Correct answer is: The baseline light absorption due to static tissues and blood
Q.16 Which parameter can be derived from a laser Doppler flowmeter that is directly proportional to blood flow?
Phase shift of the returned laser beam
Power spectral density of the returned signal
Intensity of the reflected light
Optical attenuation coefficient
Explanation - The power spectrum of the Doppler shift relates to the number of moving scatterers, which in turn is proportional to flow.
Correct answer is: Power spectral density of the returned signal
Q.17 Which of the following wavelengths is typically used for the infrared channel in pulse oximetry?
590 nm
660 nm
770 nm
940 nm
Explanation - Infrared light at ~940 nm is less absorbed by hemoglobin, providing a suitable baseline for the two‑wavelength method.
Correct answer is: 940 nm
Q.18 What is the primary advantage of using ultrasound Doppler over thermodilution for measuring blood flow?
Higher spatial resolution
No need for invasive catheterization
Direct measurement of velocity profiles
Lower cost
Explanation - Ultrasound Doppler is non‑invasive, avoiding the risks and complications of catheter‑based methods like thermodilution.
Correct answer is: No need for invasive catheterization
Q.19 Which of the following best explains why a pulse oximeter may show a 'white-out' during severe hypoxia?
Loss of arterial pulsation
Overwhelming absorption of both wavelengths by deoxyhemoglobin
Device calibration error
Skin pigmentation interfering with light transmission
Explanation - When oxygen saturation is very low, deoxyhemoglobin absorbs both red and infrared light, resulting in little change in signal amplitude and a white-out appearance.
Correct answer is: Overwhelming absorption of both wavelengths by deoxyhemoglobin
Q.20 Which of the following is NOT an effect of melanin on pulse oximetry?
Reduces light transmission leading to lower signal
Shifts the optimal wavelength for measurement
Increases the likelihood of motion artifacts
Has negligible effect at standard wavelengths
Explanation - Melanin primarily attenuates light but does not directly cause motion artifacts; the other options reflect its influence on signal strength and wavelength choice.
Correct answer is: Increases the likelihood of motion artifacts
Q.21 In the Fick principle for cardiac output measurement, the flow (Q) is calculated as:
Q = (VO₂ × 1000) / (CaO₂ - CvO₂)
Q = (VO₂ × 1000) / (CaO₂ + CvO₂)
Q = VO₂ × (CaO₂ - CvO₂) × 1000
Q = (CaO₂ + CvO₂) / VO₂ × 1000
Explanation - The Fick principle relates oxygen consumption to arterial‑venous oxygen difference and cardiac output.
Correct answer is: Q = (VO₂ × 1000) / (CaO₂ - CvO₂)
Q.22 Which parameter is typically derived from the PPG waveform to assess vascular compliance?
Pulse transit time
Amplitude ratio of systolic to diastolic peaks
Area under the curve
Pulse wave velocity
Explanation - Pulse wave velocity (PWV), calculated from transit time over distance, reflects arterial stiffness and compliance.
Correct answer is: Pulse wave velocity
Q.23 Which of the following best describes the 'phase difference method' in laser Doppler flowmetry?
It uses phase lag between reflected and transmitted laser light to calculate flow
It measures time delay between two wavelengths of light
It compares phase of AC and DC components in PPG
It determines flow by analyzing the phase shift in a frequency‑modulated laser
Explanation - Phase difference between reflected and transmitted beams in LDF indicates scatterer motion and is related to flow.
Correct answer is: It uses phase lag between reflected and transmitted laser light to calculate flow
Q.24 In a standard pulse oximeter, the sample rate is typically:
50 Hz
100 Hz
200 Hz
500 Hz
Explanation - Most commercial pulse oximeters sample the photodiode output at around 100 samples per second to capture heart rate and SpO₂ accurately.
Correct answer is: 100 Hz
Q.25 Which of the following best explains the 'half‑width' of a PPG pulse peak?
Time between maximum and minimum amplitude
Duration of the peak at 50 % of its amplitude
Distance from baseline to peak amplitude
Rate at which the pulse rises to its peak
Explanation - Half‑width measures how long the pulse remains above half of its peak, indicating pulse shape and arterial health.
Correct answer is: Duration of the peak at 50 % of its amplitude
Q.26 Which device is used to measure capillary refill time (CRT) and is often paired with pulse oximetry?
Tachometer
Photoplethysmograph
Lung auscultator
Peripheral perfusion monitor
Explanation - Peripheral perfusion monitors assess CRT, complementing SpO₂ by evaluating microvascular perfusion.
Correct answer is: Peripheral perfusion monitor
Q.27 Which of the following is NOT a component of the standard 3‑lead ECG used to confirm pulse oximetry readings?
Lead I
Lead II
Lead III
Lead V3
Explanation - The standard 3‑lead ECG uses leads I, II, and III; V3 is part of the 12‑lead configuration.
Correct answer is: Lead V3
Q.28 What is the most significant clinical concern if a pulse oximeter reads a SpO₂ of 75 % in a patient?
Hyperventilation
Severe hypoxemia
Electrolyte imbalance
Cardiac tamponade
Explanation - A SpO₂ of 75 % indicates dangerously low oxygenation requiring immediate intervention.
Correct answer is: Severe hypoxemia
Q.29 Which parameter is derived from the slope of the PPG waveform during diastole?
Heart rate
SpO₂
Arterial stiffness
Respiratory rate
Explanation - The diastolic decay slope relates to arterial compliance; a steep slope indicates stiffness.
Correct answer is: Arterial stiffness
Q.30 Which of the following best describes a 'photodiode' in a pulse oximeter?
An optical sensor that converts light into an electrical signal
A light source that emits two wavelengths
A filter that isolates the red wavelength
A processor that calculates SpO₂
Explanation - The photodiode detects transmitted light intensity and converts it into a voltage for processing.
Correct answer is: An optical sensor that converts light into an electrical signal
Q.31 What is the primary advantage of using a near‑infrared spectroscopy (NIRS) probe over a standard pulse oximeter?
Measuring arterial blood pressure
Assessing regional tissue oxygenation
Calculating cardiac output
Providing a 24‑hour heart rate monitor
Explanation - NIRS monitors oxygen saturation in deeper tissues, not just arterial blood as with pulse oximetry.
Correct answer is: Assessing regional tissue oxygenation
Q.32 Which of the following best explains why a pulse oximeter cannot accurately measure oxygen saturation in the presence of carbon monoxide poisoning?
CO binds to hemoglobin and alters its absorption spectrum
CO increases the heart rate, affecting the sensor
CO reduces skin perfusion
CO causes electromagnetic interference with the device
Explanation - Carboxyhemoglobin absorbs light similarly to oxyhemoglobin, misleading the two‑wavelength algorithm.
Correct answer is: CO binds to hemoglobin and alters its absorption spectrum
Q.33 Which signal processing technique is commonly used to remove baseline wander from a PPG signal?
High‑pass filtering
Low‑pass filtering
Band‑stop filtering
Median filtering
Explanation - A high‑pass filter removes slow baseline drift while preserving the pulsatile component.
Correct answer is: High‑pass filtering
Q.34 Which of the following is a typical clinical use of Doppler ultrasound in arterial blood flow measurement?
Detecting arrhythmias
Evaluating peripheral arterial disease
Measuring capillary refill time
Assessing blood pH
Explanation - Doppler ultrasound helps diagnose stenosis, occlusion, and blood flow deficits in peripheral arteries.
Correct answer is: Evaluating peripheral arterial disease
Q.35 In pulse oximetry, the ratio of transmitted to incident light at 660 nm is directly related to:
Oxygen saturation
Blood pressure
Heart rate
Skin temperature
Explanation - The ratio of light absorption at red wavelengths reflects the proportion of oxyhemoglobin.
Correct answer is: Oxygen saturation
Q.36 Which of the following is a common artifact that causes the pulse oximeter to display a low SpO₂ reading in a patient with cyanosis?
High ambient light
High hematocrit
Low SpO₂ measurement error due to melanin
Cold extremities
Explanation - Very high hematocrit increases absorption and reduces transmitted light, falsely lowering SpO₂ readings.
Correct answer is: High hematocrit
Q.37 Which of the following best explains the difference between arterial and venous oxygen saturation?
Arterial oxygen saturation is always higher than venous due to oxygen extraction in tissues
Venous oxygen saturation is higher because of deoxygenated blood
Arterial oxygen saturation is lower due to capillary diffusion
Venous oxygen saturation equals arterial oxygen saturation in healthy individuals
Explanation - Blood releases oxygen at tissues, so arterial SpO₂ (~95‑100 %) is higher than venous (~70‑75 %).
Correct answer is: Arterial oxygen saturation is always higher than venous due to oxygen extraction in tissues
Q.38 The 'time delay' between the ECG R‑wave and the peak of the PPG pulse is used to calculate:
Heart rate
Pulse transit time
SpO₂
Respiratory rate
Explanation - Pulse transit time (PTT) is the interval between electrical depolarization and peripheral pulse arrival, related to arterial stiffness.
Correct answer is: Pulse transit time
Q.39 What is the primary function of the 'optical filter' in a pulse oximeter's light source?
To convert light to an electrical signal
To block unwanted wavelengths and allow only the desired wavelengths
To amplify the transmitted light
To regulate the temperature of the LEDs
Explanation - Optical filters isolate the specific red and infrared wavelengths necessary for accurate SpO₂ measurement.
Correct answer is: To block unwanted wavelengths and allow only the desired wavelengths
Q.40 Which parameter is most directly influenced by the compliance of a large artery in a Doppler flow study?
Flow velocity peak
Velocity profile shape
Mean velocity
Doppler frequency shift
Explanation - Compliant arteries allow a more parabolic velocity profile; stiff arteries produce flatter profiles.
Correct answer is: Velocity profile shape
Q.41 The 'signal‑to‑noise ratio' (SNR) in a photoplethysmographic signal is important because:
It determines the maximum heart rate that can be measured
It affects the accuracy of SpO₂ calculations
It indicates the level of skin pigmentation
It sets the sampling frequency
Explanation - A high SNR ensures that the pulsatile component can be reliably extracted for SpO₂ determination.
Correct answer is: It affects the accuracy of SpO₂ calculations
Q.42 Which of the following is a key safety consideration for patients undergoing laser Doppler flowmetry?
Laser power must be below the maximum permissible exposure (MPE)
The device must not be used near the eyes
It must be performed under general anesthesia
The probe should not exceed 5 cm in length
Explanation - Safety protocols limit laser intensity to avoid ocular or skin damage during LDF measurements.
Correct answer is: Laser power must be below the maximum permissible exposure (MPE)
Q.43 Which of the following is NOT a typical signal artifact in a pulse oximeter?
Motion artifact
Ambient light interference
Electrical noise
Hemodynamic changes
Explanation - Hemodynamic changes are real physiological signals; artifacts are extraneous disturbances.
Correct answer is: Hemodynamic changes
Q.44 When measuring blood flow in the femoral artery, which imaging modality provides the most accurate velocity profile?
Thermographic imaging
Capacitance plethysmography
Spectral Doppler ultrasound
Pulse oximetry
Explanation - Spectral Doppler directly captures velocity across the vessel cross‑section, giving the best velocity profile.
Correct answer is: Spectral Doppler ultrasound
Q.45 Which of the following factors can cause a pulse oximeter to report an SpO₂ of 98 % in a patient actually having a saturation of 90 %?
Presence of methemoglobin
High ambient light
Use of a high‑sensitivity sensor
Low hematocrit
Explanation - Methemoglobin absorbs light similarly to oxyhemoglobin, leading to falsely high SpO₂ readings.
Correct answer is: Presence of methemoglobin
Q.46 Which of the following best describes the 'half‑width of the PPG pulse' in terms of cardiovascular health?
A longer half‑width indicates arterial stiffness
A shorter half‑width indicates arterial stiffness
It is unrelated to arterial health
It indicates heart rhythm disturbances
Explanation - Arterial stiffness reduces pulse wave dispersion, resulting in a sharper, narrower pulse.
Correct answer is: A shorter half‑width indicates arterial stiffness
Q.47 In the context of flow measurement, the 'continuity equation' states that:
Flow = Pressure × Volume
Flow = Cross‑sectional area × Velocity
Flow = Volume / Time
Flow = (Pressure difference) / Resistance
Explanation - The continuity equation expresses that volume flow rate equals area times average velocity.
Correct answer is: Flow = Cross‑sectional area × Velocity
Q.48 Which of the following is a potential consequence of using an incorrectly sized sensor in a pulse oximeter?
Inaccurate SpO₂ readings due to poor light transmission
Increased battery life
Improved heart rate accuracy
Higher noise floor in ECG signal
Explanation - Mismatched sensor size leads to suboptimal contact and light path, distorting the signal.
Correct answer is: Inaccurate SpO₂ readings due to poor light transmission
Q.49 Which of the following is a key difference between capillary refill time and pulse oximetry?
CRT measures venous blood flow; SpO₂ measures arterial
CRT is a visual assessment; SpO₂ is a quantitative sensor
CRT uses electrical signals; SpO₂ uses optical signals
CRT is continuous; SpO₂ is intermittent
Explanation - CRT is a simple bedside test, while SpO₂ provides continuous, numeric saturation data.
Correct answer is: CRT is a visual assessment; SpO₂ is a quantitative sensor
Q.50 Which of the following best describes why a pulse oximeter may not work well in patients with severe anemia?
Low hemoglobin reduces light absorption, diminishing signal
Anemia changes skin color interfering with sensors
Anemia increases heart rate beyond sensor limits
Anemia alters the wavelength absorption of oxygenated blood
Explanation - Less hemoglobin means less light absorption, making the AC signal weaker and more susceptible to noise.
Correct answer is: Low hemoglobin reduces light absorption, diminishing signal
Q.51 Which of the following is a primary advantage of using photoplethysmography over electrocardiography for heart rate monitoring in infants?
PPG is less invasive and more comfortable
ECG provides better accuracy in low heart rates
PPG can measure blood pressure directly
ECG is easier to interpret in noisy environments
Explanation - PPG uses a small sensor, making it suitable for delicate infant skin where ECG leads may be difficult to place.
Correct answer is: PPG is less invasive and more comfortable
Q.52 Which of the following best explains why a pulse oximeter might be inaccurate during vigorous exercise?
Increased ambient temperature
Motion artifacts due to body movement
Higher oxygen consumption
Reduced skin pigmentation
Explanation - Rapid movement disturbs sensor contact and induces noise, affecting SpO₂ accuracy.
Correct answer is: Motion artifacts due to body movement
Q.53 Which of the following is a direct measurement of vascular resistance?
Pulse transit time
Pulse wave velocity
Mean arterial pressure divided by cardiac output
SpO₂
Explanation - Vascular resistance equals MAP divided by CO per the Ohm’s law analogue for circulation.
Correct answer is: Mean arterial pressure divided by cardiac output
Q.54 What is the effect of adding a high‑pass filter at 0.5 Hz in a PPG signal processing pipeline?
It removes high‑frequency noise
It eliminates baseline drift while preserving heartbeat
It blocks the heart rate signal
It enhances low‑frequency components
Explanation - A 0.5 Hz high‑pass filter removes slow baseline wander yet keeps the ~1 Hz heart rate signal.
Correct answer is: It eliminates baseline drift while preserving heartbeat
Q.55 Which of the following is a typical clinical application of laser Doppler flowmetry?
Measuring intracranial pressure
Assessing skin microvascular perfusion
Evaluating pulmonary artery pressure
Detecting arrhythmias
Explanation - LDF is widely used to study microcirculation in skin for conditions like diabetes and sepsis.
Correct answer is: Assessing skin microvascular perfusion
Q.56 Which of the following parameters is NOT directly measurable by a standard pulse oximeter?
SpO₂
Heart rate
Respiratory rate
Perfusion index
Explanation - Standard pulse oximeters derive HR and SpO₂ but not respiratory rate; additional algorithms can estimate it.
Correct answer is: Respiratory rate
Q.57 Which of the following best describes the role of the photodiode output in a pulse oximeter?
It is filtered to isolate the AC component
It is used to calibrate the LED brightness
It provides a direct measure of skin temperature
It generates the green wavelength needed for SpO₂ calculation
Explanation - The photodiode output contains AC (pulsatile) and DC components; filtering isolates AC for SpO₂ computation.
Correct answer is: It is filtered to isolate the AC component
Q.58 In flow measurement, what is the primary limitation of using a Doppler probe on small peripheral vessels?
Low signal amplitude due to small diameter
High power consumption
Increased risk of tissue damage
Inability to detect flow direction
Explanation - Smaller vessels produce weaker Doppler signals, challenging accurate velocity measurement.
Correct answer is: Low signal amplitude due to small diameter
Q.59 Which of the following best explains why pulse oximeters are less accurate at low perfusion states?
LEDs fail to emit enough light
The photodiode saturates at low light levels
Reduced AC signal amplitude makes ratio calculation less reliable
Blood becomes more viscous
Explanation - When perfusion is low, the AC component is weak, increasing the error in SpO₂ calculation.
Correct answer is: Reduced AC signal amplitude makes ratio calculation less reliable
Q.60 Which of the following is an essential component of a calibration protocol for a pulse oximeter?
Testing with a high‑altitude hypoxia chamber
Using a phantom with known oxygen saturation
Measuring the heart rate of a healthy volunteer
Adjusting the LED current to match device specifications
Explanation - Calibration requires a controlled medium with a known SpO₂ to verify device accuracy.
Correct answer is: Using a phantom with known oxygen saturation
Q.61 In the measurement of cardiac output by thermodilution, the indicator used is:
Heat
Color dye
Sound wave
Radioactive tracer
Explanation - Thermodilution injects a cold saline bolus; changes in blood temperature are used to compute cardiac output.
Correct answer is: Heat
Q.62 Which of the following best describes the 'pulse wave velocity' (PWV) measurement?
Time delay between ECG R‑wave and PPG peak
Frequency of heartbeats per minute
Ratio of arterial to venous blood volume
Amplitude of the PPG waveform
Explanation - PWV is calculated from the transit time of the pulse wave between two arterial sites.
Correct answer is: Time delay between ECG R‑wave and PPG peak
Q.63 Which of the following is NOT a typical source of error in laser Doppler flowmetry?
Skin pigmentation
Motion artifacts
Ambient temperature fluctuations
Probe angle misalignment
Explanation - While temperature can affect blood flow, it does not directly alter the LDF signal; motion, skin, and angle are key errors.
Correct answer is: Ambient temperature fluctuations
Q.64 What is the primary advantage of using a photoplethysmograph for monitoring in neonatal intensive care units?
It measures blood pressure non‑invasively
It provides continuous heart rate and oxygen saturation
It can detect arrhythmias with high sensitivity
It can measure blood glucose levels
Explanation - PPG-based pulse oximetry offers continuous, non‑contact monitoring crucial for fragile neonates.
Correct answer is: It provides continuous heart rate and oxygen saturation
Q.65 Which of the following best explains why a pulse oximeter reading might be unreliable in a patient with severe anemia and cyanosis?
Low hemoglobin concentration reduces signal strength
Cyanosis increases ambient light absorption
Anemia interferes with LED brightness
Cyanosis causes electrical interference
Explanation - Anemia lowers blood absorption, weakening the AC signal and making SpO₂ calculation less reliable.
Correct answer is: Low hemoglobin concentration reduces signal strength
Q.66 Which of the following best describes the 'half‑width at half maximum' (HWHM) of a PPG pulse?
Time duration from baseline to peak
Time duration at half the pulse amplitude
Amplitude difference between systolic and diastolic peaks
Distance between successive peaks
Explanation - HWHM quantifies the width of the pulse at 50 % of its maximum, indicating pulse shape.
Correct answer is: Time duration at half the pulse amplitude
Q.67 Which of the following is a major challenge when measuring blood flow in the carotid artery using Doppler ultrasound?
High pressure causing probe displacement
Large vessel diameter leading to low signal
Deep location requiring high‑frequency transducers
Rapid blood flow causing aliasing
Explanation - High velocity can exceed the Nyquist limit, resulting in aliasing artifacts that distort velocity readings.
Correct answer is: Rapid blood flow causing aliasing
Q.68 Which of the following best describes the term 'photoplethysmographic pulse wave velocity'?
Velocity of light through skin
Time delay between two PPG signals at different sites
Speed of blood flow in a capillary
Rate of oxygen saturation changes
Explanation - PPG‑PWV is derived from the transit time between two PPG sensors placed at known distances.
Correct answer is: Time delay between two PPG signals at different sites
Q.69 What is the significance of the 'DC component' in the context of pulse oximetry?
It represents arterial oxygen saturation
It accounts for venous blood and tissue absorption
It indicates the heart rate
It measures skin temperature
Explanation - DC component reflects the constant absorption of light by tissues, used as a baseline for AC extraction.
Correct answer is: It accounts for venous blood and tissue absorption
Q.70 Which of the following is a key safety consideration for a pulse oximeter's LED power?
It must be below the maximum permissible exposure for skin and eyes
It should match the ambient lighting conditions
It must be adjustable by the user
It should be as high as possible for stronger signals
Explanation - LED intensity is limited to avoid tissue heating or ocular damage during prolonged use.
Correct answer is: It must be below the maximum permissible exposure for skin and eyes
Q.71 Which of the following is the most accurate non‑invasive method for measuring blood oxygen saturation?
Pulse oximetry
Co‑oximetry via spectroscopy
Capillary blood gas analysis
Near‑infrared spectroscopy (NIRS)
Explanation - Co‑oximetry, typically in a clinical lab, uses multiple wavelengths to quantify various hemoglobin species accurately.
Correct answer is: Co‑oximetry via spectroscopy
Q.72 Which of the following best explains why a pulse oximeter may produce a low SpO₂ reading in a patient with a high concentration of methemoglobin?
Methemoglobin absorbs at both wavelengths, confusing the algorithm
Methemoglobin increases the heart rate
Methemoglobin reduces skin perfusion
Methemoglobin emits its own light
Explanation - Methemoglobin's absorption overlaps with oxyhemoglobin, leading to erroneous SpO₂ values.
Correct answer is: Methemoglobin absorbs at both wavelengths, confusing the algorithm
Q.73 Which of the following is the primary limitation of capillary refill time as a perfusion assessment tool?
Subjective interpretation
Requires special equipment
Cannot be performed on neonates
Imprecise measurement of blood flow rate
Explanation - CRT depends on the clinician's visual assessment, making it less objective than instrumental methods.
Correct answer is: Subjective interpretation
Q.74 What is the typical sampling interval (in milliseconds) for a pulse oximeter that measures heart rate at 100 Hz?
1 ms
5 ms
10 ms
20 ms
Explanation - At 100 Hz, the time between samples is 1/100 s = 10 ms.
Correct answer is: 10 ms
Q.75 Which of the following best describes the function of the 'optical encoder' in a Doppler ultrasound system?
It encodes the frequency shift into a digital signal
It converts time delay into distance
It generates the acoustic wave
It measures the echo amplitude
Explanation - The encoder processes the Doppler shift to produce a readable velocity value.
Correct answer is: It encodes the frequency shift into a digital signal
Q.76 In the context of blood flow, what does the term 'Laminar flow' refer to?
Random, turbulent movement of blood cells
Smooth, orderly flow with velocity gradient
Flow that occurs only in veins
Blood flow with alternating directions
Explanation - Laminar flow has a parabolic velocity profile and occurs at low Reynolds numbers.
Correct answer is: Smooth, orderly flow with velocity gradient
Q.77 Which of the following is a major advantage of using a photoplethysmographic sensor for monitoring in an operating room?
It provides direct blood pressure readings
It can monitor both heart rate and oxygen saturation continuously
It eliminates the need for anesthesiologist oversight
It can detect blood glucose levels
Explanation - PPG sensors give continuous SpO₂ and HR, vital for patient safety during surgery.
Correct answer is: It can monitor both heart rate and oxygen saturation continuously
Q.78 Which of the following best explains why a pulse oximeter might be inaccurate in a patient wearing nail polish?
Polish blocks infrared light transmission
Polish alters the LED current
Polish increases skin pigmentation
Polish causes motion artifacts
Explanation - Nail polish can absorb infrared light, diminishing signal transmission to the photodiode.
Correct answer is: Polish blocks infrared light transmission
Q.79 Which of the following is a key determinant of the 'noise floor' in a pulse oximeter?
Skin pigmentation
Ambient temperature
Ambient light
Patient age
Explanation - Unfiltered ambient light increases baseline noise, raising the noise floor and affecting accuracy.
Correct answer is: Ambient light
Q.80 What is the typical range of wavelengths used in near‑infrared spectroscopy (NIRS) for monitoring tissue oxygenation?
400–500 nm
600–700 nm
800–900 nm
950–1100 nm
Explanation - NIRS typically uses wavelengths in the 800–900 nm range for deep tissue penetration.
Correct answer is: 800–900 nm
Q.81 Which of the following best describes the 'duty cycle' of an LED in a pulse oximeter?
Ratio of on-time to off-time in each cycle
The duration of the light pulse
The frequency of light emission
The intensity of the LED
Explanation - Duty cycle determines how often the LED is active, affecting power consumption and signal strength.
Correct answer is: Ratio of on-time to off-time in each cycle
Q.82 Which of the following is NOT a common method for determining peripheral perfusion?
Perfusion index from pulse oximetry
Capillary refill time
Skin temperature gradient
Blood pressure cuff inflation
Explanation - Cuff inflation is used for blood pressure, not direct perfusion assessment.
Correct answer is: Blood pressure cuff inflation
Q.83 Which of the following best explains why a pulse oximeter can display a sudden drop in SpO₂ during a short movement?
The sensor loses contact and reduces light transmission
The LED current is automatically decreased
The heart rate increases, affecting saturation
Ambient temperature changes the sensor electronics
Explanation - Movement can cause the sensor to shift, temporarily cutting off light transmission and lowering SpO₂.
Correct answer is: The sensor loses contact and reduces light transmission
Q.84 Which of the following best describes the 'cross‑correlation method' in pulse wave analysis?
It aligns two waveforms to find time delay
It calculates the average amplitude of a waveform
It measures the frequency content of a signal
It determines the phase shift between two signals
Explanation - Cross‑correlation compares two signals to find the lag time, used in PWV calculations.
Correct answer is: It aligns two waveforms to find time delay
Q.85 In a typical pulse oximeter, what is the purpose of the 'integrator' circuit?
To accumulate signal over time for improved SNR
To convert light intensity to voltage
To filter high‑frequency noise
To adjust LED brightness automatically
Explanation - An integrator smooths the signal, reducing noise before further processing.
Correct answer is: To accumulate signal over time for improved SNR
Q.86 Which of the following is a typical limitation of Doppler ultrasound for measuring flow in microcirculation?
Large penetration depth
Insufficient spatial resolution
High power consumption
Invasive probe insertion
Explanation - Ultrasound resolution limits its ability to resolve very small vessels or capillaries.
Correct answer is: Insufficient spatial resolution
Q.87 What is the primary clinical indication for using a near‑infrared spectroscopy (NIRS) device?
Monitoring arterial blood pressure
Assessing tissue oxygenation in critical care
Measuring heart rate
Estimating blood glucose levels
Explanation - NIRS monitors regional oxygen saturation, useful in ICU and peri‑operative settings.
Correct answer is: Assessing tissue oxygenation in critical care
Q.88 Which of the following best explains why pulse oximeters may have difficulty in patients with high hemoglobin concentrations?
High hemoglobin increases signal amplitude beyond device range
High hemoglobin reduces light absorption
High hemoglobin causes interference with LED wavelength
High hemoglobin increases ambient temperature
Explanation - Very high hemoglobin can produce a strong absorption, leading to signal saturation and inaccurate SpO₂.
Correct answer is: High hemoglobin increases signal amplitude beyond device range
Q.89 Which of the following best describes the role of the 'rectifier' in a photoplethysmographic signal chain?
To convert the AC signal into a DC signal for measurement
To filter out high‑frequency noise
To amplify the signal
To convert light into an electrical signal
Explanation - Rectification removes negative portions of the waveform, enabling DC‑DC conversion for processing.
Correct answer is: To convert the AC signal into a DC signal for measurement
Q.90 In flow measurement, which equation relates flow (Q), cross‑sectional area (A), and velocity (v)?
Q = A × v
Q = v / A
Q = A × v²
Q = v × (A²)
Explanation - Continuity states that flow equals area times average velocity.
Correct answer is: Q = A × v
Q.91 Which of the following best explains why a pulse oximeter might show a 'white-out' during severe hypoxia?
Loss of arterial pulsation
Overwhelming absorption of both wavelengths by deoxyhemoglobin
Device calibration error
Skin pigmentation interfering with light transmission
Explanation - When SpO₂ is very low, deoxyhemoglobin absorbs both red and infrared light, causing little change in signal amplitude and a white-out appearance.
Correct answer is: Overwhelming absorption of both wavelengths by deoxyhemoglobin
Q.92 Which of the following is NOT an advantage of using photoplethysmography for pulse monitoring?
Non‑invasive
No requirement for electrodes
No need for skin contact
High tolerance to motion artifacts
Explanation - PPG requires skin contact to transmit light; it is non‑invasive but still needs physical contact.
Correct answer is: No need for skin contact
Q.93 Which of the following best explains why a pulse oximeter may be inaccurate in a patient with methemoglobinemia?
Methemoglobin absorbs light similarly to oxyhemoglobin, confusing the algorithm
Methemoglobin reduces skin temperature
Methemoglobin increases pulse rate
Methemoglobin blocks light transmission entirely
Explanation - Methemoglobin’s absorption spectrum overlaps with oxyhemoglobin, leading to over‑estimated SpO₂.
Correct answer is: Methemoglobin absorbs light similarly to oxyhemoglobin, confusing the algorithm
Q.94 Which of the following is the most common artifact affecting pulse oximeter readings during surgical procedures?
Ambient light from operating lamps
Patient motion and surgical manipulation
Electromagnetic interference from monitors
All of the above
Explanation - Surgical environments introduce multiple artifacts, all of which can affect SpO₂ accuracy.
Correct answer is: All of the above
Q.95 What is the typical range for the perfusion index in a healthy adult?
0.1–0.5
0.5–3
3–10
10–20
Explanation - Perfusion index values around 1–3 are typical in well‑perfused adults.
Correct answer is: 0.5–3
Q.96 Which of the following best describes a 'laser Doppler flowmeter'?
An optical device that measures changes in light intensity due to moving red blood cells
An ultrasound probe that detects velocity via frequency shift
A device that uses infrared spectroscopy to assess oxygenation
A pressure sensor that measures blood flow indirectly
Explanation - Laser Doppler flowmetry uses laser light scattered by moving red blood cells to assess microcirculation.
Correct answer is: An optical device that measures changes in light intensity due to moving red blood cells
Q.97 Which of the following is a major limitation of thermodilution cardiac output measurement?
High invasiveness
Requires large volumes of cold saline
Cannot be used in patients with arrhythmias
All of the above
Explanation - Thermodilution is invasive, needs significant fluid, and is unreliable in irregular heart rhythms.
Correct answer is: All of the above
Q.98 Which of the following best describes how pulse oximetry determines heart rate?
By counting peaks in the AC component of the PPG waveform
By measuring the time interval between R‑waves on ECG
By analyzing the DC component of the photodiode signal
By detecting the change in skin temperature
Explanation - The heart rate is derived from the frequency of the pulsatile AC signal in the PPG.
Correct answer is: By counting peaks in the AC component of the PPG waveform
Q.99 Which of the following is a common physiological variable that can be derived from the time delay between ECG R‑wave and the PPG pulse peak?
Pulse transit time (PTT)
Pulse wave velocity (PWV)
SpO₂
Perfusion index
Explanation - PTT is the time from electrical depolarization to peripheral pulse arrival, related to arterial stiffness.
Correct answer is: Pulse transit time (PTT)
Q.100 Which of the following best explains why a pulse oximeter may be less accurate in patients with dark skin pigmentation?
Melanin absorbs infrared light, reducing signal
Dark skin reduces the AC component amplitude
Melanin increases the baseline DC component
All of the above
Explanation - Higher melanin levels increase absorption, leading to weaker signals and potential inaccuracies.
Correct answer is: Melanin absorbs infrared light, reducing signal
Q.101 Which of the following is the main advantage of using a Doppler probe over a pulse oximeter for assessing arterial blood flow?
Direct measurement of flow velocity and direction
Non‑invasive continuous oxygen monitoring
Lower cost
Higher sensitivity to skin pigmentation
Explanation - Doppler ultrasound directly measures velocity and can assess flow direction, beyond SpO₂.
Correct answer is: Direct measurement of flow velocity and direction