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

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 (\bar{{\rm d}}) to be {-}{\rm 38.9}~{\rm 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 worse \bar{{\rm d}}:{-}{\rm 40.6}~{\rm ml} and {-}{\rm 54.8}~{\rm 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.