Theoretical study on the effect of sensor contact force on pulse transit time

Area of Science:

• Biomedical Engineering
• Cardiovascular Physiology
• Medical Instrumentation

Background:

• Pulse transit time (PTT) noninvasively assesses arterial viscoelastic properties like elasticity and stiffness.
• PTT is typically measured between the electrocardiogram R wave peak and photoplethysmogram (PPG) foot.
• Photoplethysmogram signals are sensitive to the contact force applied by sensors.

Purpose of the Study:

• To investigate the impact of varying contact forces on PTT measurements.
• To analyze the nonlinear biomechanical properties of the finger arterial wall under different pressures.
• To understand how arterial pressure-volume curve shape changes influence PTT.

Main Methods:

• Utilized computational simulations incorporating nonlinear biomechanical properties of arterial walls.
• Focused on analyzing alterations in the arterial wall pressure-volume curve.
• Validated theoretical findings through experimental measurements on human subjects.

Main Results:

• Simulations showed PTT increases with contact force at positive transmural pressure.
• PTT reached maximum values at zero transmural pressure.
• PTT remained constant under negative transmural pressure conditions.
• Experimental data from 30 young and 6 elderly subjects corroborated simulation findings across 12 contact force levels.

Conclusions:

• Contact force significantly influences PTT measurements, particularly under varying transmural pressures.
• Understanding arterial nonlinear biomechanics is crucial for accurate PTT-based vascular assessment.
• The study provides a basis for optimizing PTT measurement protocols for improved noninvasive cardiovascular evaluation.