Fig. 1
From: Kinematic signature of high risk labored breathing revealed by novel signal analysis
Respiratory rate and rhythm. Panels A and B show a respiratory kinematic signal from an accelerometer (A) and a synchronized volumetric air flow signal (B). The colored dots correspond to phase landmarks in the analytic representation of these signals (E), evenly spaced in phase at intervals of Ļ/2 radians. The phase of any point of the analytic signal (E) is the angle between a line joining that point to the origin and the positive x-axis. We used analytic phase landmarks to identify breath intervals and to extract an interpolated instantaneous respiratory rate series from each kinematic signal. Panel C shows 36 interpolated respiratory rate time series from one patient (6 kinematic signals per location; 6 locations). The rates extracted from clean kinematic signals converged on the true respiratory rate whereas the rates extracted from noisy kinematic signals deviated from the true respiratory rate to a varying degree. We identified the largest cluster of converging respiratory rates (thick bundle in Panel C) and adjudicated its centroid as our estimate of the respiratory rate (black line in Panel D). The final kinematics-derived rate series (black line) matched the flow-derived rate series (red line) with high fidelity. Panel F plots the kinematics-derived respiratory rate as a function of flow-derived respiratory rate in 60 paired recordings, with 95% limits of agreement of Ā±ā0.9 breaths per minute.
