A novel non-invasive, non-conductive method for measuring respiration

Jan Ringkamp,Philipp Lebhardt,Jens Langejürgen,Philipp Radler

doi:10.5194/jsss-9-27-2020

Abstract

Abstract. We present a novel method for measuring dynamic changes in respiration parameters due to breathing based on the coupling of two ultra-high-frequency (UHF) antennae. For evaluation, we built a dynamic 3-D printed phantom encasing two compartments separated by an elastic diaphragm. By filling this artificial lung with air the effective permittivity in the compartment changes, resulting in a significant variation of the S21 parameter's magnitude and phase. We show that there is a strong linear correlation between the volume of air in the artificial lung and the magnitude (in dB) of the S21 parameter (R2=0.997) as well as the parameter's phase (R2=0.975). Our sensor system shows a high reproducibility (standard deviation of predicted volume =0.67 mL) and a timing similar to a conventional flow sensor (delay =5.33 ms). The presented method is a promising candidate to overcome some of the most important technical burdens of measuring respiratory parameters and might be used as a trigger for patient–ventilator synchronization in infants and neonates.

Highlights

Respiratory parameters like breathing rate, tidal volume, or inhalation onset are among the most crucial parameters in intensive care
We present a novel method for measuring dynamic changes in respiration parameters due to breathing based on the coupling of two ultra-high-frequency (UHF) antennae
We show that there is a strong linear correlation between the volume of air in the artificial lung and the magnitude of the S21 parameter (R2 = 0.997) as well as the parameter’s phase (R2 = 0.975)

Summary

Introduction

Respiratory parameters like breathing rate, tidal volume, or inhalation onset are among the most crucial parameters in intensive care. Medical respirators need current values to adjust timing and flow rates in order to ensure an optimal and protecting ventilation of the lung. This is especially important when it comes to the ventilation of infants or neonates. In the ventilation of premature infants it is common practice to use uncuffed endotracheal tubes to prevent the development of ventilator-induced lung injury, like volu- or barotrauma (Mahmoud et al, 2015) This poses an additional challenge for respiration sensors, because the unknown leakage due to the uncuffed endotracheal tube makes simple pressure and airflow measurement highly unreliable

Methods

Results

Discussion

Conclusion