Table 2.

List of features extracted from the signals for the machine learning training. For the details of the Catch-22 features, please refer to its paper.

Feature Name	Definition
Custom Features
sig_snr	Ratio of the std of Signal(LP 20Hz)[50, 200] to Signal(LP 20Hz)[250, 500] ms.
sig-hp_cor	Correlation between Signal(BP)[0, 500] and Signal(HP 9Hz)[0, 500] ms. It shows how much the signal is correlated with noise.
response_cor	Correlation between Reference Normal Signal[0:200] and Other Signals(LP 20Hz)[0:200] ms.
std_ratio	Ratio of the std of the Signal(BP)[0:250] to Signal(HP 20Hz)[250, 500] ms.
mid_abs_auc_ratio	Ratio of AUC of ABS<Signal(LP 20 Hz)[0, 250]>/ABS<Signal(LP 20 Hz)[250, 500]> ms.
skewness	Skewness of Signal(LP 9 Hz)[0, 500] ms.
peak_amp_ratio_13	The ratio of the amplitude of the highest peak (positive or negative) to 3rd highest peak (positive or negative) on Signal(BP)[0, 500] ms.
peak_amp_ratio_14	The ratio of the amplitude of the highest peak (positive or negative) to the 4th highest peak (positive or negative) on Signal(BP)[0, 500] ms.
no_zero_x	The number of zero-crossings of Signal(BP)[0, 500] ms.
fft_resp_to_alpha_power	The ratio of the power of the alpha frequency band of the signal [8~13 Hz] peak to the [0~8Hz] frequency band peak, based on FFT analysis on the Signal(BP)[0, 500] ms.
wv_apprx_std_0	std(first half of level 1 DWT approx. coefficients of the Signal(BP)[0, 500] ms.)
wv_apprx_std_1	std(first half of level 2 DWT approx. coefficients of the Signal(BP)[0, 500] ms.)
Catch-22 Features
CO_f1ecac	On Signal(BP)[0:500] ms. First 1 / e crossing of the autocorrelation function.
CO_FirstMin_ac	On Signal(BP)[0:500] ms. First minimum of the autocorrelation function.
MD_hrv_classic_pnn40	On Signal(BP)[0:500] ms. The proportion of successive differences exceeding 0.04σ.
DN_OutlierInclude_p_001_mdrmd	On Signal(BP)[0:500] ms. Time intervals between successive extreme events above the mean.
DN_OutlierInclude_n_001_mdrmd	On Signal(BP)[0:500] ms. Time intervals between successive extreme events below the mean.
SB_BinaryStats_diff_longstretch0	On Signal(BP)[0:500] ms. The longest period of successive incremental decreases.
SB_MotifThree_quantile_hh	On Signal(BP)[50:200] ms. Shannon entropy of two successive letters in equiprobable 3-letter symbolization.

Abbreviations: LP: Low Pass Filter, BP: Band Pass [3~50 Hz] Filter, HP: High Pass Filter, AUC: Area Under the Curve, ABS: Absolute value, FFT: Fast Fourier Transfer, DWT: Discrete Wavelet Transform