Table 1 Studies for Pain Assessment Using Physiological Signals

EMG

Acute

Volunteers

40 (20M 20F)

Not provided

(S) Electrical: electrodes. Thermal -heat-: water

NFR

NRS

Jurth et al., 2014²⁶

ECG

Acute

Patients

Not provided

Not provided

Contractions during labour

ECG frequency spectrum analysis

VAS

Chu et al., 2024⁹¹

Volunteers

52 (26M 26F)

18-36

(S) Thermal -heat-: thermode block

HRV (RRI, LnRMSSD, LF, HF)

N/A

Tracy et al., 2018⁴⁰

Volunteers

123 (48M 75F)

22.43 ± 2.94

(S) Thermal -cold-: CPT

HRV: Log-transformed LF and HF

NRS

Umeda & Okifuji³⁹

Chronic: chronic musculoskeletal, neuropathic, …

Patients

363 (119M 244F)

56.3 ± 14.01

Chronic pain resting state

HRV: IBI, HR, SDNN, RMSSD, pNN50, HRV triangular index, TINN, LF, HF, LF/HF

VAS / NRS

Moens et al., 2023³⁷

Perioperative

Patients

80

Not provided

Surgery

ANI

EAPS

Jean et al., 2022⁹⁷

Post-operative

Patients

107 (46M 61F)

37.4 ± 15

Postoperative pain

ANI

NRS

Abdullayev et al., 2019³⁵

Post-operative: caesarean

Patients

40 (40F)

Not provided

(T) Pharmacologic: analgesics

HR, sympathetic tone, vagal tone

VAS

Deepika & Brindha, 2015¹⁰⁶

PPG

Acute

Volunteers

22 (10M 12F)

27 ± 4.19

(S) Electrical: TENS

Time and freq domain feat., PRV (HF, LF, VLF, NN50, pNN50, NN20, pNN20, SDSD, RMSSD, SDNN)

VAS

Khan et al., 2023⁹³

Chronic: radiculopathy, NSBP, FBSS, CRPS

Patients

20 (15M 5F)

52.25 ± 9.77

(T) Neuromodulation: SCS

PPGA number of changes, PRV (PR min, PR max, PR median, SDNNI, SDANN, RMSSD)

NRS

Patterson et al., 2023⁸⁸

Nociception / Post-operative

Patients

242 (117M 125F)

58.4 ± 10.6

Pre vs postsurgical pain

60 (median, max and min values) morphological, spatiotemporal, interval and dynamic feat.

NRS

Ryu et al., 2024⁵⁴

Post-operative

Patients

65 (28M 37F)

50.5 ± 10.5

Pre vs postsurgical pain

PA, Asys, Adia, TriA, TriAsys, and TriAdia, ACAdia, ACAbl, Lsys, Ldia, RS, LRS, RSmax, FS, LFS, Pulse Width, PPIsys, PPIdia, ACVsys

VAS

Yang et al., 2018⁴⁷

Patients

89 (41M 48F)

54.4 ± 12.9

(T) Pharmacologic: oxycodone

PPGA, PAnorm, SYSvar, DIAvar, HBIvar, PA

NRS

Cho et al., 2018⁵³

Patients

100

53 ± 12.4

Pre vs postsurgical pain

Pulse height, rise time, fall time, average HR, PRV (HF, LF, VLF, LF/HF, AVNN, SDNN, RMSSD, NN20, pNN20, NN50, pNN50)

NRS

Lim, 2019⁵⁶

Patients

100 (44M 56F)

53.4 ± 12.5

(T) Pharmacologic: oxycodone

2D spectrogram. SPI

VAS

Choi et al., 2021¹⁰⁷

Patients

99 (99F)

Not provided

(T) Pharmacologic: tramadol

SPI

NRS

Hamed et al., 2024¹⁰⁸

EDA

Acute

Patients

20 (11M 9F)

54.45 ± 17.44

(S) Electrical: TENS. Mechanical: walk, cough, sit up

SCR (number of peaks, mean, max, range, dPhEDA, IQR, RMS, mean minima, mean maxima) using cvxEDA

NRS

Aqajari et al., 2021⁶⁴

Volunteers

40 (23M 17F)

25

(S) Electrical: TENS

Amplitude of SCR, SPR, and SSR: SPRET; SCR_Trise

NRS

Bari et al., 2018⁶⁰

Volunteers

23 (11M 12F)

24.5 ± 4.8

(S) Thermal -heat/cold-: grill

SCR, SCL, and dPhEDA from cvxEDA and sparsEDA approaches. TVSymp and MTVSymp

VAS

Posada-Quintero et al., 2021⁶¹

Volunteers

16 (7M 9F)

25.6 ± 4.8

(S) Electrical

SCR, SCL, and dPhEDA from cvxEDA, sparsEDA, CDA, DDA, and DCM approaches. TVSymp and MTVSymp.

NRS

Kong et al., 2021⁶³

Volunteers

23 (23M)

Not provided

(S) Thermal -cold- and intradermal capsaicin(T) Analgesics, placebo

SCL

VAS

Bhatkar et al., 2022⁶²

Volunteers

29

Not provided

(S) Thermal -cold-: CPT

SCL (mean, SD, range, AUC) and SCR (mean, SD, range, peak max, peak min, peak sum, peak num, duration mean, slope mean, AUC) from cvxEDA. Whole signals

NRS

Pouromran et al., 2022⁶⁵

Volunteers

38 (17M 21F)

Not provided

(S) Thermal -heat/cold-: grill

SCR, TFS-phEDA from cvxEDA

N/A

Pinzon-Arenas et al., 2023⁶⁶

Patients

53 (26M 27F)

36.2

(S) Thermal -cold-. Electrical (dental)(T) Local anaesthesia

TVSymp (max, peak, mean)

VAS

Tran et al., 2023⁶⁹

Acute / Chronic: TMJ disorders

Volunteers

/ Patients

24 (4M 20F). 12 (PMED) - 12 chronic.

27 ± 11

(S) Thermal -heat-: thermode blockTMJ therapy

SCR and SCL (median, SD, min, max, 1st and 2nd derivative)

VAS

Badura et al., 2024¹⁰⁹

EEG

Acute

Patients

30 (13M 17F)

29-73.

(S) Laser Pulse

Mean IPI variability, LEP latency and amplitude,

NCS-R

Naro et al., 2017⁷⁷

Volunteers

9 (7M 2F)

Not provided

(S) Mechanical: hand pressure application

Delta, Theta, Alpha, low Gamma and Beta (decomposed into 4 bands).

NRS

Okolo & Omurtag, 2018⁷¹

Volunteers

62 (30M 32F)

Young: 22.95 ± 3.58. Old: 68 ± 6.

(S) Thermal -heat-: hot air.

Delta, Theta, Alpha, low Gamma, high Gamma and Beta bands. GBO

VAS

Zhou et al., 2020⁷²

Volunteers

13 (8M 5F)

20-52

(S) Electrical: TENS

HFD-based (HFD, HFD_ACF, HFD_VAR), GP-based (GP, GP_ACF, GP_VAR), Correlation-based (HFD, HFD_ACF, GP_ACF), VAR-based (GP, HFD_VAR, GP_VAR)

N/A

Tripanpitak et al., 2020⁷⁵

Volunteers

20 (17M 3F)

27.4 ± 5.7

(S) Thermal -cold-: CPT

Delta, Theta, Alpha, low Gamma, and Beta bands.

VAS

Wang et al., 2020⁷⁴

Volunteers

32 (12M 20F)

19-35

(S) Thermal -cold-: CPT

Delta, Theta, Alpha, low Gamma, and Beta bands.

NRS

Yu et al., 2020⁹⁹

Volunteers

20 (11M 9F)

23-42

(S) Thermal -cold-: CPT

Delta, Theta, Alpha, Beta, and low Gamma bands.

NRS

Yu et al., 2020⁹⁴

Volunteers

24 (17M 7F)

21

(S) Thermal -cold-: CPT

Spatial spectral-temporal signal analysis

VAS

Wu et al., 2022¹¹⁰

Volunteers

36 (14M 22F)

25.36 (20-56)

(S) Thermal -heat-: hot water

Alpha band (peak, individual alpha frequency) with closed and open eyes

VAS

Valentini et al., 2022¹¹¹

Volunteers

28 (10M 18F)

29.23 ± 13.83

(S) Topical capsaicin. (T) Electrical: rTMS, AiTBS

Delta, Theta, Alpha, Beta, and low Gamma bands.

VAS

Tan et al., 2024¹¹²

Volunteers

12 (12F)

20.4 ± 0.9

(S) Electrical: electrodes.

Evoked Potentials amplitude and latency.

NRS, QST

Chen et al., 2023¹¹³

Volunteers

80 (46M 34F)

25.2 ± 2.06

(S) Thermal -cold-: CPT. (T) Electrical: TENS, tDCS.

Spectral power density analysis in Alpha, Delta, Theta, Beta and Gamma bands.

NRS

Mujib et al., (2024)¹¹⁴

Patients

33 (21M 12F)

7.41 ± 3.38

(S) Mechanical: Arterial puncture.

Pre-processed signal.

N/A

Fu et al., (2024)¹¹⁵

Volunteers / Patients

86 (49M 57F)

27.9 ± 1.9 weeks

(S) Mechanical: skin breaking procedures done in NICU

Somatosensory Evoked Potentials waves and scores.

N/A

Coviello et al., 2024¹¹⁶

Chronic: joint, widespread, back, neuropathic.

Volunteers

/Patients

Patients. 101 (32M 69F). Control. 88 (28M 60 F).

Patients. 58.1 ± 13.6. Control. 57.5 ± 14.2.

Patients vs control group

Signal global field power peaks.

painDETECT / PDI

May et al., 2021¹¹⁷

Chronic: LBP

Patients

27 (7M 20F)

44.6 ± 2.3

Chronic pain resting state

ABO (eyes closed, eyes open and normalised).

VAS

Feng et al., 2021⁷⁶

Chronic: posttraumatic headache

Volunteers / Patients

Patients. 26 (21M 5F). Control. 20 healthy (13M 7F)

Patients. 41.9 ± 11.1. Control. 40.7 ± 15.5

Evoked potentials

Evoked Potentials amplitude

VAS

Jessen et al., 2024¹¹⁸

Chronic: Cancer related pain

Patients

3

55-75

(T) Music Therapy

Delta, Theta, Alpha, low Gamma, and Beta bands.

NRS

Hunt et al., 2021¹¹⁹

Chronic: osteoarthritis, lower back pain

Patients

4 (1M 3F)

85-92

Chronic pain resting state

Detrended fluctuation analysis of the signal.

PAINAD scale

Pu et al., 2021¹²⁰

Chronic: trigeminal and postherpetic neuralgia, spinal cord injury …

Volunteers

/ Patients

211 (101M 110F)

18-85

Chronic pain resting state

Pi.

VAS / NRS

An et al., 2017⁷³

fNIRS

Acute

Volunteers

30 (23M 7F)

31.7 ± 8.7

(T) Electrical: TENS

10 statistical features from ΔHbO2 and ΔHHB each

NRS

Khan et al., 2024⁸⁰

Chronic: cervical shoulder syndrome

Patients

20 (20M)

36.6 ± 7.2

(S) Mechanical: Pressure application

(T) Electrical: TENS

HbO

VAS

Du et al., 2023⁷⁸

Chronic: Osteoarthritis

Patients

30

50–85

(T) Neuromodulation: tDCS+MBM(S) Thermal -heat-: thermode block

HbO

NRS

Pollonini et al., 2020⁷⁹

ECG, EDA

Acute

Volunteers

BioVid Database (Part A – 67 subj.)

Not provided

(S) Thermal -heat-: thermode block

Whole pre-processed signal

N/A

Subramaniam & Dass, 2021¹⁰⁰

Volunteers

30 (15M 15F)

34 ± 11.9

(S) Thermal -heat-. Electrical

EDA. Max, average, AUC and SD of SCR and SCL from cvxEDA. Phasic driver (average rise time, number of peaks, max peak amplitude). ECG. HR (mean, median), HRV (SDNN, RMSSD, LF).

N/A

Jiang et al., 2024³⁶

Volunteers

BioVid Database (Part C - 87 subj.)

Not provided

(S) Thermal -heat-: thermode block

EDA. 11 statistical features. ECG. HR, HRV (SDNN, RMSSD)

N/A

Jiang et al., 2024¹⁰¹

Chronic: Cancer-related pain

Patients

Case1. 1 F. Case2. 1 M.

Case1. 66. Case2. 74

(T) Opioids. Neuromodulation: PENS and HF.

EDA. SCR (latency, sum, average) ISCR. ECG. RR (mean, SD).

NRS

Cascella et al., 2023³²

Chronic: cancer-related pain

Patients

64

60.6 ± 13.3

(T) Pharmacologic: Opioids, pain adjuvants

EDA. Mean amplitude of CDA and TTP. ECG. HR, HRV (RRI, SDNN)

NRS

Cascella et al., 2024²⁸

ECG, Face Exp

Acute

Volunteers

BioVid Database (Part A – 87 subj)

Not provided

(S) Thermal -heat-: thermode block

Whole pre-processed signal

N/A

Gkikas et al., 2024¹²¹

ECG, PPG

Acute

Volunteers

20 (10M 10F)

26.5 ± 6.4

(S) Thermal -heat-: thermode block

PTT, PPGA

NRS

N van Velzen et al., 2015⁴⁵

Volunteers

Trial. 30 (14M 16F). C. 10 (7M 3F)

Trial. 22.5 ± 1.9. C. 22.5 ± 1.3

(S) Thermal -heat-: water

ECG. RRI, HR, HRV. PPG. PPGA, BL, ANSS

NRS

Ye et al., 2017⁵²

Volunteers

25 (11M 14F). 22.44 ± 1.85 years.

22.44 ± 1.85

(S) Thermal -heat-: water

PPG. PPGA, BL, ANNS. ECG. HRV (RRI, HF, LF, LF/HF, SDNN)

NRS

Jhang et al., 2021³¹

Chronic: cervical, lumbar

Patients

66 (23M 43F)

62.86 ± 12.10

(T) Electrical: RFT

ECG. HR, RRI, short HRV (LF, HF, VLF, normalised LF, normalised HF, LF/HF). PPG. PPGA, BL, PPI, ANSS, SSI.

VAS

Ye et al., 2017²⁹

Chronic: Myofascial Pain Syndrome

Patients

37 (10M 27F)

41.84 ± 13.68

(T) Electrical &Thermal -heat-: thermotherapy

HRV (ECG) and PRV (PPG): HR, mean RRI, SDNN, RMSSD, VLF, LF, HF, LF/HF. PPG: PPGA, SPI, ANSS, ANSSi, BL

VAS

Ye et al., 2018³⁰

Intraoperative / post-operative

Patients

40 (34M 6F)

36.86 - 37.86 weeks

Surgery: open and laparoscopic inguinal hernia repair.(T) Analgesics

NIPE Monitor Index

N/A

Sakthivel et al., 2024¹⁷

Patients

78 (31M, 47F)

51.8 ± 10.9

(T) Pharmacologic: Opioids

60 morphological, spatiotemporal, interval and dynamic feat.

VAS

Seok et al., 2019⁸⁴

Patients

192 (84M 108F)

54 ± 12

Pre vs postsurgical pain

PPG. SPI. EEG. ANI

NRS

Lee et al., 2019³⁴

ECG, PPG, BP

Acute

Volunteers

11 M

22.8 ± 1.7

(S) Electrical

BP, PPG (PPGA). PPG/ECG/BP. Arterial stiffness index

NRS

Matsubara et al., 2018⁴⁹

Post-operative

Patients

30 (19M 11F).

42 ± 5

(T) Pharmacologic: sufentanil

PPG. AC, DC, AC/DC. BP.SBP, DBP, MAP. ECG. Heart rate.

VAS

Ling et al., 2014⁴¹

ECG, PPG, EDA

Acute

Volunteers

6 (4M 2F)

22-25 ± 3

(S) Electrical

12 statistical feat.: means; SD; means of the abs values of the first differences and the norm signals; means of the abs values of the second differences and the norm signals; min and max values; min and max ratios; range; median.

VAS

Chu et al., 2017⁸⁵

ECG, PPG, fMRI

Acute

Volunteers

EXP1. 30 (30M). EXP2. 22 (22M).

EXP1. 23.5 ± 1.4EXP2. 22.7 ± 1.0

(S) Electrical

Arterial Stiffness

NRS and VAS

Tsuji et al., 2021⁵⁰

EDA, Face Exp

Chronic: PIFP

Patients

Trial. 67. Control. 28.

Not Provided

Trial vs control group

VAS

Rokicki et al., 2022¹²²

Post-operative

Patients

45 (31M 14F)

5-17

(S) Mechanical: manual abdominal pressure

EDA. TSD triangular matrix (mean, SD, entropy). SCL (SD)

NRS

Susam et al., 2022⁹²

EDA, Self-Assessment

Intraoperative/ post-operative

Patients

15 (4M 11F)

63.73 ± 7.85

Pre vs postsurgical pain

EDA. SCR

NRS

MacNeill & Mayich (2020)¹²³

EEG, ECG, Resp

Acute

Volunteers

18 (8M 10F)

27.22 ± 4.03

(S) Electrical. (T) Virtual reality hypnosis

EEG. Evoked potentials and time-frequency responses. ECG. HRV (RRI, HR, RMSSD). Resp.

VAS

Rousseaux et al., (2023)¹²⁴

EMG, ECG, EDA

Acute

Volunteers

BioVid Database

Not Provided

(S) Thermal -heat-: thermode block

Amplitude, freq, stationarity, entropy, linearity, and variability derived features from EMG (Zygomaticus, corrugator and trapezius muscle), EDA (SC), ECG (HR, interbeat interval, HRV)

N/A

Walter et al., 2014²⁴

Gruss et al., 2015²⁵

Volunteers

BioVid Database

Not Provided

(S) Thermal -heat-: thermode block

Whole pre-processed signal

N/A

Thiam et al., 2019⁹⁸

Volunteers

BioVid Database

Not Provided

(S) Thermal -heat-: thermode block

22 time-series feat. (each): distribution, simple temporal statistics, linear and nonlinear autocorrelation, successive differences, fluctuation analysis.

N/A

Pouromran et al., 2021⁶⁷

Volunteers

BioVid Database (Part B - 86 subj.)

Not Provided

(S) Thermal -heat-: thermode block

155 feat. including amplitude, variability, stationarity, entropy, linearity, similarity and freq.

N/A

Albahdal et al., 2024⁸⁷

EMG, ECG, EDA, Face Expr, Audio

Acute

Volunteers

X-ITE Database (127 subj.)

18-50

(S) Electrical. Thermal -heat-: thermode block

Time-series statistic descriptor of the signals (1st & 2nd derivative, min, max, mean, SD).

VAS

Othman et al., 2022⁹⁵

Othman et al., 2023⁹⁶

Acute

Volunteers

X-ITE Database (127 subj.)

18-50

(S) Electrical. Thermal -heat-: thermode block

Whole pre-processed signal.

VAS

Gruss et al., 2019²¹

ECG, PPG, EDA, Resp

Acute

Volunteers /Patients

Volunteers. 52 (17M 35F). Patients. 20 (5M 15F).

Volunteers. 27.4 ± 6.6. Patients. 40.9 ± 14.4

(S) Thermal -heat-: thermode block

ECG (Mean, SDNN, RRI slope, RMSSD, number of R peaks), Resp (Number & mean amplitude of phases), PPG (PR)., EDA (SCR, SCL, dPhEDA, TVSymp). Max, min, range, SD, interquartile range, mean, local max and min for all.

VAS

Khan et al., 2023⁸²

EMG, ECG, PPG, EEG, Face Exp

Acute

Patients

109 (56M 53F)

4 (1–23) days

(S) Mechanical: heel lances

Reflex withdrawal, HR, SPO2, facial expression responses, noxious-evoked brain activity.

N/A

Van der Vaart., 2019⁸⁶

EMG, EDA

Acute

Volunteers

BioVid Database

Not Provided

(S) Thermal -heat-: thermode block

EMG (zygomaticus). FF, RMS, ZCD. EDA. SCR (slope)

N/A

Sen & Pal, 2021¹²⁵

EMG, PPG, EDA, EEG, BP, Resp, Face Exp

Acute

Volunteers

26 (7M 19F)

20.7 ± 2.4

(S) Thermal -cold-: CPT

EEG. Frequency bands (delta, theta, alpha, beta, gamma), GD, EB, HEM, VEM. EDA (SC), PPG (PR), BP (Diastolic, systolic), Pupillometry (Pupil Dilation)

NRS

Lin et al., 2022²³

PPG, EDA, Resp

Acute

Volunteers

22 (10M 12F)

27 ± 4.19

(S) Electrical: TENS

PPG. Rate (mean, amplitude), PRV (time, freq, nonlinear domain feat.). EDA. SCR (number of peaks, max, amplitude (mean, median, SD, max, min, range, interquartile range metrics). Resp. Rate variability, sinus arrhythmia, amplitude (min, max, mean), rate (min, mean, max, min and max time).

VAS

Fernandez-Rojas et al., 2023⁵⁷

PPG, EDA, Temp, Acc

Acute / Chronic: Upper limb CRPS

Patients

20 (8M 12F)

48.4 ± 9.2

(S) Mechanical: physiotherapy.

NOL Index

NRS

Santella et al., 2022¹⁶

Post-operative / Acute

Patients

54 (39M 15F)

65.76 ± 11.77

(S) Mechanical: non-invasive BP, chest tube removal

NOL Index

NRS

Gélinas et al., 2021¹⁵

PPG, EEG

Post-operative

Patients

98 (50M 48F)

62.9 ± 12.8

Pre vs postsurgical pain

PPG. PI. EEG. BIS

VAS

Kwon et al., 2019⁵¹

Pupillometry

Post-operative / Chronic

Patients

18 (4M 14F)

21-72

(T) Pharmacologic: analgesics. Surgery

PUAL

NRS

Behrends & Larson., 2024⁸³