Continuous limb blood flow estimation in the newborn using electrical impedance plethysmography

Area of Science:

• Biomedical Engineering
• Neonatal Physiology
• Medical Instrumentation

Background:

• Continuous limb blood flow monitoring in neonates is crucial for assessing physiological status.
• Existing methods for blood flow measurement can be invasive or difficult to automate.
• Developing non-invasive, automated techniques is essential for neonatal care.

Purpose of the Study:

• To establish a method for continuous, automatically processable limb blood flow data acquisition in newborns.
• To compare the efficacy of pulsatile electrical impedance and strain gauge techniques for neonatal blood flow measurement.
• To validate a new impedance-based method against established plethysmography techniques.

Main Methods:

• Analysis of pulsatile electrical impedance and strain gauge signals in 33 newborn infants.
• Comparison of impedance and strain gauge measurements with venous occlusion plethysmography using a mercury-in-rubber strain gauge.
• Evaluation of measurement reproducibility and linear regression analyses between different flow estimates.

Main Results:

• The electrical impedance technique was simpler to perform than the strain gauge method.
• Beat-to-beat reproducibility was superior with impedance recordings compared to strain gauge recordings.
• Flow calculated from impedance pulse height, F(Zmax), showed the best correlation (r = 0.76) with venous occlusion plethysmography, with an intercept close to zero.

Conclusions:

• The measurement of impedance pulse height (delta Zmax) and calculation of F(Zmax) can be automated.
• This automated impedance technique provides reliable, continuous, beat-to-beat blood flow estimations in newborns.
• The method offers a promising non-invasive approach for neonatal hemodynamic monitoring.