The effect of local cold exposure on pulse transit time

Area of Science:

• Biomedical Engineering
• Physiology
• Medical Devices

Background:

• Pulse transit time (PTT) is a key indicator for noninvasive blood pressure (BP) monitoring.
• Developing reliable PTT-based BP devices requires understanding factors affecting PTT measurement accuracy.
• Local temperature variations, such as cold exposure, can influence physiological signals.

Purpose of the Study:

• To investigate the impact of localized finger cold exposure on PTT.
• To compare the reliability of different PTT measurement definitions under cold stress.
• To assess the suitability of PTT for continuous BP monitoring in varying environmental conditions.

Main Methods:

• 13 healthy subjects underwent a 2-minute finger cold water immersion (9±2°C).
• Photoplethysmographic (PPG) signals were recorded simultaneously from cooled and adjacent non-cooled fingers.
• PTT was calculated using three different definitions, referencing the ECG R-wave and PPG pulse fiducial points.

Main Results:

• Cold exposure had minimal effect on PTT measured to the PPG pulse foot (PTT1).
• PTT measured to the PPG pulse peak (PTT3) was significantly affected by cold exposure.
• Differences in PTT between cooled and non-cooled fingers varied depending on the PTT definition used.

Conclusions:

• PTT measurement terminating at the PPG pulse foot is robust against local cold exposure.
• PTT measurements terminating at the PPG pulse peak are susceptible to cold-induced changes.
• Careful selection of fiducial points is crucial for accurate and reliable PTT-based noninvasive BP monitoring.