Comparison of heart rate measurement protocols used during autonomic function tests

Area of Science:

• Physiology
• Cardiovascular Research
• Autonomic Nervous System Function

Background:

• The cold pressor test (CPT) is commonly used to assess autonomic nervous system (ANS) function.
• Standard CPT protocols often involve averaging heart rate (HR) over various time intervals.
• The accuracy of these averaged HR measures in reflecting true physiological responses is not fully understood.

Purpose of the Study:

• To compare the accuracy of five common CPT heart rate averaging protocols against true R-R interval measurements.
• To determine the impact of different averaging durations on the assessment of autonomic responses during CPT.
• To identify optimal HR measurement strategies for sensitive detection of autonomic changes.

Main Methods:

• Forty-one healthy, nonsmoking males (18-55 years) underwent a cold hand pressor test.
• Heart rate was measured using true R-R interval analysis.
• Comparisons were made with HR data averaged over 2-, 5-, 6-, 10-, and 30-second intervals.

Main Results:

• No significant resting physiological differences were observed between participants.
• Longer HR averaging times (e.g., 10s, 30s) significantly diminished maximum stress values (P < 0.05).
• Recovery phase underestimation of true response increased with longer averaging times (P < 0.05).
• A 6-second average showed an 18% decrease in peak response time compared to R-R intervals, obscuring rapid autonomic shifts.

Conclusions:

• Averaging heart rate over extended intervals (especially >6s) during CPT reduces sensitivity and obscures the speed of autonomic nervous system changes.
• For precise and sensitive assessment of autonomic function, R-R interval measurement or 2-second averaged data are recommended.
• The choice of HR measurement protocol significantly impacts the interpretation of autonomic responses to stress.