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The effect of local mild cold exposure on pulse transit time
Xin-Yu Zhang1, Yuan-Ting Zhang
1Joint Research Center for Biomedical Engineering, Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
Physiological Measurement
|May 18, 2006
Summary
Mild cold exposure significantly affects pulse transit time (PTT) measurements, potentially introducing errors in blood pressure monitoring. This study highlights the need to consider temperature effects when using PTT, especially in wearable health devices.
Area of Science:
- Biomedical Engineering
- Physiology
- Cardiovascular Research
Background:
- Pulse transit time (PTT) is a noninvasive method for monitoring blood pressure and arterial stiffness.
- Peripheral circulation is sensitive to temperature, potentially impacting PTT accuracy.
- Wearable healthcare devices increasingly utilize PTT for continuous health assessment.
Purpose of the Study:
- To investigate the impact of mild cold exposure on PTT measurements.
- To assess the reliability of PTT in the presence of altered peripheral blood circulation.
- To identify potential sources of error in PTT-based health monitoring due to temperature variations.
Main Methods:
- PTT was measured using electrocardiogram (ECG) and photoplethysmography (PPG) signals.
- One finger was immersed in cold water while PPG signals were recorded from both cooled and adjacent uncooled fingers.
- PTT was calculated from the ECG R-wave to three distinct points on the PPG waveform (foot, maximal slope, peak).
Main Results:
- Cold exposure caused significant changes in PPG signal amplitudes, indicating altered finger blood circulation.
- PTT measurements (PTT1 and PTT2) showed significant differences between cooled and uncooled fingers post-recovery.
- PTT changes on the reference finger correlated strongly with systolic blood pressure (SBP) changes, unlike those on the cooled finger.
Conclusions:
- Mild cold exposure can delay PTT due to cold-induced vasodilation, acting as a potential error source.
- PTT measurements, particularly those including the rising time of the peripheral pulse, require careful examination under varying temperature conditions.
- The findings emphasize the importance of controlling for temperature variations in PTT-based blood pressure and arterial stiffness assessments.
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