CPE Physiological Monitoring 3 — Questions and Answers
Question 1: In polygraph cardio recordings, relative blood pressure (RBP) is considered 'relative' because:
- It measures only diastolic pressure, not systolic
- It records changes in arterial wall movement rather than true mmHg values (Correct answer)
- It compares left-arm pressure to right-arm pressure simultaneously
- It is calculated as a percentage of the subject's maximum heart rate
Correct answer: It records changes in arterial wall movement rather than true mmHg values
RBP is called 'relative' because the arm cuff records changes in arterial expansion (cardiograph waveforms) rather than calibrated absolute pressure values in mmHg.
Question 2: Which autonomic branch is primarily responsible for producing the physiological responses that polygraph instruments measure during a deceptive response?
- Parasympathetic nervous system (rest-and-digest)
- Sympathetic nervous system (fight-or-flight) (Correct answer)
- Somatic motor system controlling voluntary muscles
- Enteric nervous system governing gut motility
Correct answer: Sympathetic nervous system (fight-or-flight)
The sympathetic nervous system drives the fight-or-flight response, causing the increases in EDA, heart rate, blood pressure, and respiratory changes detected by the polygraph.
Question 3: A 'suppression' response in the EDA channel is characterized by:
- A sharp upward deflection immediately following a question
- A flattening or decrease in EDA activity compared to the resting level (Correct answer)
- Rhythmic oscillations in skin conductance unrelated to questions
- A slow upward drift lasting 15–20 seconds post-question
Correct answer: A flattening or decrease in EDA activity compared to the resting level
Suppression in EDA refers to a reduction or flattening of activity, sometimes associated with countermeasures or a strong inhibitory response.
Question 4: What is the significance of measuring BOTH thoracic and abdominal respiration channels in a polygraph exam?
- Redundancy ensures one channel always produces a signal regardless of subject position
- It allows detection of differential breathing shifts that may indicate countermeasure use or suppression (Correct answer)
- Only one channel is actually scored; the second is for equipment calibration
- Abdominal breathing is monitored only in female subjects per APA guidelines
Correct answer: It allows detection of differential breathing shifts that may indicate countermeasure use or suppression
Monitoring both channels allows examiners to detect shifts between chest and belly breathing patterns, which may signal deliberate breath control or other countermeasures.
Question 5: A photoplethysmograph (PPG) sensor used in some polygraph systems primarily detects:
- Electrical impedance of the skin surface
- Volumetric changes in blood flow through peripheral capillaries via infrared light (Correct answer)
- Muscle electrical potentials from flexor tendons
- Skin surface temperature using a thermistor
Correct answer: Volumetric changes in blood flow through peripheral capillaries via infrared light
PPG uses infrared light to detect changes in blood volume in peripheral tissues such as the fingertip, providing an alternative or supplementary cardiovascular channel.
Question 6: In polygraphy, 'hyperventilation' before or during a test is considered significant because it:
- Reduces EDA activity and eliminates relevant-question responses
- Can suppress physiological reactions and lower CO2, potentially masking deceptive responses (Correct answer)
- Increases blood pressure to clinically dangerous levels
- Has no effect on polygraph tracings because sensors are motion-compensated
Correct answer: Can suppress physiological reactions and lower CO2, potentially masking deceptive responses
Hyperventilation reduces CO2 levels, which can blunt physiological responsivity and is therefore recognized as a potential countermeasure that may reduce detectable deceptive responses.
Question 7: The 'inter-beat interval' (IBI) in cardiovascular polygraph data refers to:
- The time between the systolic and diastolic peaks within a single heartbeat
- The time elapsed between consecutive heartbeats (R-to-R interval) (Correct answer)
- The difference in amplitude between two successive cardiograph waves
- The latency between a question stimulus and the first EDA peak
Correct answer: The time elapsed between consecutive heartbeats (R-to-R interval)
IBI is the time interval between successive heartbeats (R-to-R), and variations in IBI reflect heart rate variability, which is an emerging measure in some polygraph research.
CPE Physiological Monitoring 3
In polygraph cardio recordings, relative blood pressure (RBP) is considered 'relative' because: