Table 1 The characteristics of included studies

McCaughey EJ, et al. 2019

critically ill mechanically ventilated participants

NMES = 10

CG = 10

58.75 ± 15.33

NR

NR

NMES for 30 min, twice daily, 5 days per week, until ICU discharge. NMES was on the dominis and internal and external oblique muscles, with stimulation frequency of 30 Hz, pulse width of 350 us, and at an intensity was able to cause a strong visible muscle contraction (median 60 mA [range 50–65 mA])

ventilation duration, ICU LOS, ICU mortality, extubation success rate.

6-month

Jonkman AH, et al. 2020

mixed ICU ventilated patients within 72 hours after intubation

NMES = 10

CG = 10

68.95 ± 8.51

26.35 ± 4.40

NR

NMES was on the abdominal wall for 30 min twice daily, 5 days per week, until patients were weaned from mechanical ventilation, but no longer than 6 weeks, with stimulation frequency of 30 Hz, pulse width of 352 us, and at an intensity was able to cause strong muscle contraction, with a maximum intensity initially set at 60–100 mA.

ventilation duration, ICU LOS, and ICU mortality

until weaned from MV, but shorter than 6 weeks

Abu-Khaber HA, et al. 2013

ICU patients

with MV for more than 24 hours

NMES = 40

CG = 40

58.32 ± 6.11

NR

25.3 ± 6.11

NMES was simultaneously on the quadriceps muscles of both lower extremities for 1 h once daily, starting from the second day after admission until ICU discharge, with stimulation frequency of 50 Hz, pulse width of 200 μs and at intensity able to cause visible contractions (mostly 100–150 MA).

ventilation duration, 28 days mortality, extubation success rate

28 days or until the time of weaning from MV

Study

Patients

Number of participants

Age (years), mean ± SD

Baseline BMI (kg/m²), mean ± SD

Baseline APACHE II, mean ± SD

Application of NMES

Measurement timepoint

outcomes

Koutsioumpa et al. 2018

Adult patients use of mechanical ventilation for 96 hours or more.

NMES+PT = 38

PT = 42

65.05 ± 12.73

27.00 ± 6.51

19.1 ± 7.97

NMES was simultaneously on the quadriceps muscle of each lower extremity for 1 h once daily from the 4th to the 14th ICU Day, with impulses of 50 Hz per 500 ms phase duration, at intensities able to cause visible muscle contractions.

ventilation duration, 28-day mortality.

10 days

Hsin YF, et al. 2022

Participants on ventilation for ≥21 days

NMES = 29

CG = 30

75.23 ± 10.50

22.76 ± 4.62

18.39 ± 3.97

Transcutaneous electrical diaphragmatic stimulation intervention for 30 min/day, 5 days/week until the end of the weaning trial, with stimulation frequency of 30 Hz, pulse width of 400 us, at an intensity was gradually increased until visible muscle contraction was observed.

ventilation duration, mortality, extubation success

the end of the weaning trial

Chen YH, et al. 2019

Participants on ventilation for ≥21 days

NMES = 16

CG = 17

75.69 ± 16.07

23.00 ± 4.72

20.54 ± 6.75

NMES was on motor points of the vastus lateralis and rectus femoris of both legs, for 30-min twice per day, 5 days per week for 2 weeks, with simulation frequency of 50 Hz, pulse width of 400 us, and the intensity was gradually increased until a visible muscle contraction was observed.

ventilation duration, mortality, extubation success

2 weeks

Study

Patients

Number of participants

Age (years), mean ± SD

Baseline BMI (kg/m²), mean ± SD

Baseline APACHE II, mean ± SD

Application of NMES

Measurement timepoint

outcomes

Leite MA, et al.2018

Patients on MV for 24 hours or more.

NMES+PT = 41

PT = 26

44.41 ± 18.72

23.34 ± 8.52

18.57 ± 3.23

Subjects received NMES were randomized into two groups: diaphragm group (DG) or quadriceps group (QG). NMES was performed on the right and left sides of the xiphoid process within the seventh and eighth anterior intercostal space, with a frequency of 30 Hz for DG, and on quadriceps with frequency of 50 Hz for QG. Each session was performed for 45 min daily at intensities that produced visible contractions.

ventilation duration, ICU length of stay

NR

Shen SY, et al. 2017

Patients required MV longer than 72 hours

NMES+PT = 18

PT = 7

77.64 ± 6.73

NR

23.92 ± 6.08

NMES was on both quadriceps and biceps, for 32 minutes per day, 5 days per week. The stimulator output current was 0–75 mA in biphasic waves with carrier frequency of 1500 Hz. The lowest stimulation current was given to induce visible muscle contraction.

ventilation duration, hospital mortality, extubation success

NR

Dall’ Acqua AM, et al. 2017

Patients hospitalized for no longer than 15 days and had received

MV for

24–48 hours

NMES+PT = 11

PT = 14

58.8 ± 14.09

24.44 ± 4.52

27.68 ± 6.27

NMES was performed on the chest muscles (pectoralis major muscle fibers) and rectus abdominis muscles bilaterally, for 30 min once a day, with frequency of 50 Hz, pulse duration of 300 us, and the intensity was increased until muscle contraction was visible or could be identified through palpation.

ventilation duration, ICU LOS, mortality

day 7 of MV or 24 h after extubation

Study

Patients

Number of participants

Age (years), mean ± SD

Baseline BMI (kg/m²), mean ± SD

Baseline APACHE II, mean ± SD

Application of NMES

Measurement timepoint

outcomes

Kho ME, et al.2015

Patients received MV within the first week of ICU stay

NMES+PT = 16

PT = 18

55.06 ± 16.86

27 ± 7.05

25 ± 6.90

NMES was on quadriceps, tibialis anterior, and gastrocnemius bilaterally, for 60 minutes daily, with frequency of 50 Hz, pulse duration of 250 us for the tibialis anterior and gastrocnemius, 400us for the quadriceps, at intensities able to cause visible muscle contractions.

ventilation duration, ICU LOS, hospital mortality

at hospital discharge

Dos Santos FV, et al.2020

Adults received MV for less than 72 hours, without neuromuscular disease.

NMES = 11

CG = 15

NMES+PT = 12

PT = 13

53.24 ± 12.17

NR

15.90 ± 3.54

NMES was on the rectus femoris, vastus lateralis, and vastus medialis muscles bilaterally, for 55 minutes twice a day, 7 days per week, with frequency of 45 Hz, pulse duration of400 μs, at intensities able to cause visible muscle contractions.

ventilation duration, ICU LOS, mortality

Until discharged from ICU, for a maximum duration of 6 weeks

Silva PE, et al.2019

Critically ill traumatic brain injury adults received MV for up to 24 hours

NMES+PT = 30

PT = 30

31.5 ± 11.17

NR

11 ± 3.7

NMES was on the lower limb muscles for a 30-minute session daily for 14 consecutive days, with frequency of 100 Hz, pulse duration of 400 us, at intensities to evoke maximum contractions in each muscle group.

ventilation duration, ICU LO, ICU mortality

14 days

Study

Patients

Number of participants

Age (years), mean ± SD

Baseline BMI (kg/m²), mean ± SD

Baseline APACHE II, mean ± SD

Application of NMES

Measurement timepoint

outcomes

Mahran GSK, et al. 2023

Adults required MV on the first day of admission

NMES+PT = 60

PT = 58

31.49 ± 9.49

NR

13.82 ± 6.09

NMES was on abdominal muscles for 40 minutes(20 minutes on diaphragmatic muscles and 20 minutes to the abdominal muscles) daily until the seventh day of admission, with frequency of 20 Hz, at intensities able to cause visible muscle contractions.

ventilation duration, ICU LOS, mortality

the seventh day of admission

Chen S, et al.2019

COPD patients admitted to ICU and received MV

NMES+PT = 27

PT = 29

40.34 ± 23.63

22.37 ± 1.53

19.41 ± 4.30

NMES was on the extremities for 30 minutes twice a day after 24 hours of admission until ICU discharge, with frequency of 30 ~ 40 Hz.

ventilation duration, ICU LOS

until ICU discharge

Peng, Lu, et al.2022

ICU patients received MV for more than 24 hours

NMES = 30

PT = 30

30

NMES+PT = 30

58.25 ± 14.63

19.77 ± 6.22

NR

Patients received NMES of 30 min/day, 5 days/week for 2 weeks on gastrocnemius muscles and abdominis muscles.

extubation success rate, ICU LOS, ventilation duration

2 weeks

Verceles AC, et al.2023

Older patients (> 50 years) received MV for more than 24 hours

NMES+PT = 16

PT = 23

62 ± 9.2

29.59 ± 6.12

16.38 ± 6.71

NMES was applied to the quadriceps for 30 minutes twice daily for 10 days, with frequency of 50 Hz, pulse duration of 300 us, at intensities able to cause visible muscle contractions.

ventilation duration, ICU LOS

14 days

Study

Patients

Number of participants

Age (years), mean ± SD

Baseline BMI (kg/m²), mean ± SD

Baseline APACHE II, mean ± SD

Application of NMES

Measurement timepoint

outcomes

Medrinal C,et al.2023

Adults ventilated for at least 24 hours

NMES = 30

CG = 31

62 ± 12.6

27 ± 5.47

NR

NMES was applied on diaphragm for 20 minutes daily, 5 times per week, with frequency of 50 Hz, pulse duration of 300 us, at intensities able to cause visible muscle contractions.

ventilation duration, ICU LOS, extubation success rate

until the first extubation attempt

Liu Y, et al.2023

Patients on MV for respiratory failure

NMES+PT = 40

PT = 40

58.62 ± 15.69

24.51 ± 4.69

20.17 ± 6.39

NMES was applied on the pectoralis major fibers, rectus abdominis and bilateral quadriceps muscles, for 30 minutes per day until discharged from ICU, with frequency of 50 Hz, pulse duration of 300 us, at intensities gradually increase until significant muscle contractions occur.

ventilation duration, ICU LOS, extubation success rate, mortality

at discharge from ICU

Campos DR, et al.2022

Adults less than 48 hours of ICU admission and an expected stay on MV for longer than 48 hours

NMES+PT = 34

PT = 40

44.77 ± 6.61

26.46 ± 5.50

NR

NMES was applied on the quadriceps and the tibialis anterior, once a day for 60 minutes, 5 days a week, from ICU admission until ICU discharge, with frequency of 80 Hz, pulse duration of 400 us, at intensities able to cause visible muscle contractions, and the maximum intensity was 120 mA.

ventilation duration, ICU LOS

until ICU discharge

Othman SY, et al.2023

Adults on MV and was supposed to be on MV for longer than 48 hours

NMES = 30

PT = 30

NMES+PT = 30

CG = 30

41.77 ± 0.87

30.08 ± 2.44

29.05 ± 3 .95

NMES was applied on the quadriceps for 60 min daily, from day 2 of ICU admission to day 7, with frequency of 50 Hz, pulse duration of 400 us, at intensities able to cause visible muscle contractions.

ventilation duration

7 days

Study

Patients

Number of participants

Age (years), mean ± SD

Baseline BMI (kg/m²), mean ± SD

Baseline APACHE II, mean ± SD

Application of NMES

Measurement timepoint

outcomes

Olimpio JH, et al.2023

Patients aged ≥60 years and were on MV for at least 24 hours

NMES = 21

CG = 25

66.63 ± 5.22

NR

NR

NMES was applied on the diaphragm for 30 minutes twice a day immediately after the 24-h period on IMV until extubation in spontaneous ventilatory mode, with frequency of 30 Hz, pulse duration of 400 us, at intensities able to cause visible muscle contractions.

ventilation duration, extubation success rate

until extubation in spontaneous ventilatory mode

Nakanishi N, et al.2020

Adult patients who were expected to be on MV for > 48 hours

NMES+PT = 17

PT = 19

69.31 ± 4.62

23.53 ± 3.97

23.42 ± 8.18

NMES was applied on the bilateral upper and lower limbs for 30 min daily from day 1 to day 5, with frequency of 20 Hz, at intensities able to cause visible muscle contractions. The EMS intensities used were 30 mAp (23–37 mAp) for the biceps brachii and 41 mAp (33–50 mAp) for the rectus femoris.

ventilation duration, ICU LOS

discharge from the ICU

Vieira L, et al.2023

Patients on MV secondary to traumatic brain injury

NMES = 20

CG = 20

35.6 ± 12.28

NR

16.4 ± 4.50

NMES was applied on the quadriceps muscles for 55 minutes daily for five consecutive days, with frequency of 50 Hz, pulse duration of 400 us, at intensities able to evoke maximum muscle contraction.

ventilation duration, ICU LOS, extubation success rate, mortality

7 days