Tidal Volume Measurement Through Non-Contact Doppler Radar With DC Reconstruction

Abstract

This paper describes the calibration technique for a non-contact Doppler radar to monitor respiration and tidal volume in human subjects. The detected change in sensor output, reflecting the displacement of lung movement, is found to relate linearly to tidal volume. The DC reconstruction and calibration techniques are used to extract the tidal volume measurement from the radar signal. Comparison of the radar prediction and reference tidal volumes shows the average mean difference (d) to be −38.9 ml in seated subjects and 23.5 ml in supine subjects. Other chest wall displacement measurements from piezo-electric sensors at the upper and lower torso reports worsed: −40.6 ml and −54.8 ml in seated subjects and 246.6 ml and 68.5 ml in supine subjects. The predicted volumes are not significantly affected by either frequency of respiration or variation in subjects. The results in this paper show that Doppler radar could provide a valuable tool for the noncontact and unobtrusive measurement of tidal volume in human subjects.

Non-contact measurement of respiratory function and deduction of tidal volume

“…For this purpose, a few different experiment conditions were designed to investigate the feasibility and consistency of Doppler radar on top of the works [10] under different breathing scenarios in obtaining the flow in and out corresponding to the spirometer readings. In this experiment, the subject was asked to: 1) Breathe deeply, pause, and continue to breathe deeply 2) Breathe normally followed by deep breaths 3) Breathe deeply followed by normal breathing…”

“…Further to this, capability of Doppler Radar in obtaining the respiratory tidal volume [10] has been demonstrated using the known relationship between chest wall movement and tidal volume. In other word, continuous measurement of volume in and out along with other respiration parameters Terry Caelli at Terry.Caelli@deakin.edu.au such as breathing rate, respiratory effort energy, respiration patterns and etcetera could potentially be used to assess certain breathing disorders especially it could be done in a non-contact approach.…”

“…In this paper, we extended the work [10] in capturing the flow in and out during inspiration and exhalation for three different scenarios as discussed in section III. The rest of this paper is organized as follows: Section II discusses the theoretical approach of Doppler radar in measuring the breathing activities, Section III describes the experiment mechanism for the data collection and Section IV describes the signal processing algorithms used in dealing with the Doppler radar signals.…”

Mitigation of stationary clutter in vital‐sign‐monitoring linear‐frequency‐modulated continuous‐wave radars

“…This application has a large interest in hospital scenarios; for example, to monitor cardiopulmonary activity or to improve the employment of radiotherapy [6][7][8]. Additionally, it can have a profound impact on telemedicine and telehealth environments.…”

Non-contact screening system for sleep apnea-hypopnea syndrome using the time-varying baseline of radar amplitudes

“…Until now, a screening system for SAHS using radar has been seldom described, but a non-contact tool for quantitative measurement of respiratory tidal volume with Doppler radar has been reported [7,8]. In those studies, the changes detected in sensor amplitude after calibration-reflecting the displacements of lung movement-were related linearly to tidal volumes.…”