Fig. 2

a1 respiratory flow signal, a2 phase of the flow signal extracted by the SST, a3 phase of the IHR extracted by the synchrosqueezing transform (SST), a4 instantaneous heart rate (IHR), a5 electrocardiogram, a6 synchrogram during 110–125 s, a7 synchrogram and the resulting synchrogram index (0.89) in a synchronized patient. b1 respiratory flow signal, b2 phase of the flow signal extracted by the SST, b3 phase of the IHR extracted by the SST, b4 IHR, b5 Electrocardiogram, b6 synchrogram during 110–125 s, b7 synchrogram and its synchrogram index (0.35) in a desynchronized patient