Pulse wave attenuation measurement by linear and nonlinear methods in nonlinearly elastic tubes

Area of Science:

• Biomedical Engineering
• Cardiovascular Physiology
• Fluid Dynamics

Background:

• Accurate measurement of pulse wave attenuation in arteries is crucial for understanding cardiovascular health.
• Reflections within the arterial system complicate definitive attenuation measurements.

Purpose of the Study:

• To investigate the reasons for difficulties in measuring pulse wave attenuation in elastic tubes with reflections.
• To re-examine existing measurement techniques under conditions mimicking arterial nonlinearity and strong reflections.

Main Methods:

• Utilized elastic tubes with nonlinear compliance and strong reflections, simulating physiological pulse shapes and amplitudes.
• Applied four classical linear analysis methods and a nonlinear wave separation technique to measure pressure, flow-rate, and diameter pulsations.
• Calculated forward and reverse wave attenuation from resulting waveforms.

Main Results:

• Classical linear methods yielded comparable, but scattered, attenuation estimates across frequencies, with increased scatter at higher pulse amplitudes.
• The nonlinear wave separation method's backward waveform analysis produced physically unreasonable results.
• The three-point method did not systematically overestimate attenuation as suggested in literature but showed prone to negative estimates at low harmonics with increased pulse amplitude.

Conclusions:

• A fully satisfactory method for measuring arterial pulse wave attenuation has not yet been devised.
• Despite challenges, the study provides a sensitive tool for examining arterial nonlinearities.
• Further research is needed to overcome the limitations of current measurement techniques.