TABLE 1.

Main characteristics of the studies included.

Authors and Publication year	Journal	Nationality	Population	Population Characteristics	Intervention	Comparator	Protocol duration	Main findings
Berti et al. (33)	J Bras Pneumol.	Brazil	ICU patients on MV IG: n: 16 CG: n: 19	IG: Mean age: 58.06 ± 13.81; Male/female:10/6 CG: Mean age: 55.42 ± 16.99; Male/female:13/6	MH (with a manual resuscitation bag, peak airway pressure of 40 cm H2O) and ERCC twice a day for 5 days, combined with standard nursing care.	Standard nursing care: positioning (changing the body position every 2 h throughout the day) and airway suctioning (was performed for four sets of six cycles, 15 s, six times a day)	5 days	This study reports about ICU patients on MV (mean age IG: 58.06 ± 13.81, CG: 55.42 ± 16.99; 63% male in IG, 68% male in CG). They were assessed for all 5 days of the protocol duration. The main finding is represented by the differences between groups in terms of patients weaned from MV (days 2: 0.0 vs. 37.5%; p < 0.01; days 3: 0.0 vs. 37.5%; p < 0.01; days 4: 5.3 vs. 37.5%; p < 0.05; days 5: 15.9 vs. 37.5%; p < 0.05). The ICU discharge rate was significantly higher in IG group (p < 0.05).
Cader et al. (34)	J Physiother.	Brazil	ICU patients on MV IG: n: 21 CG: n: 20	IG: Mean age: 83 ± 3; Male/female:9/12 CG: Mean age: 82 ± 7; Male/female:10/10	IMT, twice a day, 7 days a week, 5 min per session. The target regimen was to commence with a load of 30% of the participant’s maximal inspiratory pressure increasing daily by 10%.	Usual care	Weaning period (MV: IG: 3.6 ± 1.5 days; CG: 5.3 ± 1.9 days)	This study reports about ICU patients on MV (mean age IG: 83 ± 3; CG: 82 ± 7; 43% male in IG, 50% male in CG; mean weight IG: 66 ± 5; CG: 65 ± 6). They were assessed for all days of the protocol duration. The main finding is represented by the reduction of the weaning period by 1.7 days (95% CI 0.4 to 3.0) in ICU patients exposed to IMT (3.6 ± 1.5 days), as compared to usual care (5.3 ± 1.9 days). Maximal inspiratory pressure increased significantly in the IG than in the CG (MD 7.6 cmH20, 95% CI 5.8 to 9.4). The Tobin index decreased in both groups over the weaning period, with significant differences between groups (MD 8.3 br/min/L, 95% CI 2.9 to 13.7).
Cader et al. (42)	Clin Interv Aging	Brazil	ICU patients on MV IG: n: 14; CG: n: 14	IG: Mean age: 82 ± 4; Male/female: 6/8; CG: Mean age: 81 ± 6; Male/female: 7/7	Conventional physiotherapy + IMT with a threshold device: 5 min, twice daily, 7 days a week, with supplemental oxygen from the beginning of weaning until extubation.	Conventional physiotherapy	Weaning period (MV time: IG 10 days CG: 11 days)	This study reports about ICU patients on MV (mean age IG: 82 ± 4; CG: 81 ± 6; 42.86% of male in IG, 50,00% in CG). They were assessed 48 h after having undergone MV. The main finding is represented by the increase of maximum inspiratory pressure and significantly reduced the Tobin index. There was a significant and unsatisfactory increase in Tobin index for the control group (95% confidence interval [CI] −4.47 to −24.44, p = 0.002) and a satisfactory increase in maximum inspiratory pressure in the experimental group (95% CI 7.09–12.62, p = 0.001). The post-test indicated a significant reduction in Tobin index (95% CI −26.23 to −6.05, p = 0.001) and a significant increase in maximum inspiratory pressure (95% CI 4.67–10.19, p = 0.001) when compared to the control group. The authors did not find significant difference in extubation success (χ2 = 1.47; p = 0.20), although weaning duration was shorter in IG (3.64 ± 1.50 days) compared to CG (5.36 ± 1.87 days).
Chen et al. (35)	Can Respir J.	Taiwan	ICU patients on MV IPPB n: 17 IPPB + PEEP n: 16 CG: n: 17	IPPB: Mean age: 69.1 ± 11.1; Male/female: 7/10 IPPB + PEEP: Mean age: 76.4 ± 14.7; Male/female: 8/8 CG: Mean age: 72.3 ± 16.2; Male/female: 12/5	IPPB or IPPB + PEEP, target volume of 10–15 mL/kg of IBW, twice a day for 7 days, 20 min per session. Semi-Fowler’s position.	Usual care	8 days	This study reports about ICU patients on MV (mean age IPPB: 69.1 ± 11.1, IPPB + PEEP: 76.4 ± 14.7, CG: 72.3 ± 16.2; gender M/F IPPB: 10/7, IPPB + PEEP: 8/8, CG: 5/12; mean weight IPPB: 56.9 ± 12.0, IPPB + PEEP: 57.3 ± 14.5, CG: 59.4 ± 12.0). The main finding is represented by the significantly higher weaning rate in IPPB and IPPB + PEEP groups compared to control group (IPPB vs. IPPB + PEEP vs. control: 88.2 vs. 87.5 vs. 41.2%, p < 0.05). Patients in the IPPB group showed a significant increase in Tindal Volume after 7 days (pre vs. post: 240.4 ± 57.2 vs. 292.5 ± 116.3 mL, p < 0.05), while the control group showed a significant reduction (pre vs. post: 293.3 ± 168.9 mL vs. 243.9 ± 140.4 mL, p < 0.05). In the IPPB + PEEP group, a significant increase in MIP was observed after the intervention (29.9 ± 15.0 vs. 37.0 ± 16.5 cmH2O, p < 0.05).
Dong et al. (36)	BMC Pulm Med	China	ICU patients on MV IG: n: 39 CG: n: 41	IG: Mean age: 59.05 ± 17.61; Male/female: 25/14 CG: Mean age: 64.44 ± 14.72; Male/female: 23/18	Early rehabilitation therapy: six levels of rehabilitation exercises, from positioning and rotational therapy to walking near the bedside.	Standard care	3–4 days	This study reports about ICU patients on MV (mean age IG: 59.05 ± 17.6; CG: 64.44 ± 14.72; 64.10% male in IG, 56.10% male in CG; mean BMI IG: 23.18 ± 3.32; CG: 23.22 ± 3.67). They were assessed for diaphragmatic excursion and diaphragmatic thickening fraction at 1- and 4-day of MV. The main finding is represented by the improvement observed in MV duration (7.49 ± 2.59 days vs. 9.41 ± 5.32 days; p = 0.045) and a significantly shorter intubation duration (8.31 ± 2.80 days vs. 10.37 ± 5.32 days, p = 0.037). The two groups were comparable in terms of duration of ICU stay (p = NS). At 4-day MV, the IG had significantly decreased diaphragmatic thickening fraction compared to the control group (0.15 ± 0.06 g vs. 0.12 ± 0.05 g, p = 0.008).
Liu and Zhang (43)	Indian J Pharm Sci	China	ICU patients on MV IG: n: 50 CG: n: 50	IG: Mean age: 48.07 (range: 32–70); Male/female:26/24; CG: Mean age: 47.85 (range: 30–70); Male/female:24/26	Artificial airway humidification is performed every 1∼2 h. The patient’s position is changed every 2 h, turning over and knocking back to help the patient to perform active or passive joint movement. A transcutaneous electrical nerve stimulator is used to perform neuromuscular electrical stimulation. A suitable sandbag has been positioned on the belly area to exercise his respiratory muscles.	Nursing inspection 3 times a day. Symptomatic treatment may be proceeded, such as relieve cough resolve phlegm, medication, transfusion therapy and diet care, etc.	Until ICU discharge (ICU length of stay) IG: 10.47 ± 2.55 CG: 18.84 ± 5.37	This study reports about ICU patients on MV (mean age IG: 48.07 [range: 32–70]; CG: 47.85 [range: 30–70]; 50% male). They were assessed for all days of the protocol duration. The main finding is represented by the success rate of weaning in the IG which was 92.0% (p < 0.05). The incidence of VAP in the IG was significantly lower (8.0%) than that in the CG (34.0%), and the difference was statistically significant (p < 0.05). The average MV time of the CG was 13.54 ± 4.75 days, and the average MV time of the IG was 6.14 ± 2.07 days (p < 0.05). The average length of stay was 18.84 ± 5.37 days stay in the CG, while in the IG was 10.47 ± 2.55 days (p < 0.05). Compared to before treatment, the CPIS of the two groups was significantly lower after treatment (p < 0.05), and the IG was significantly lower than the CG, the difference was statistically significant (p < 0.05).
Martin et al. (37)	Critical Care	United States	ICU patients on MV IG: n: 35 CG: n: 34	IG: Mean age: 65.6 ± 11.7; Male/female: 16/19 CG: Mean age: 65.1 ± 10.7; Male/female: 15/19	IMT: 5 days per week with a threshold inspiratory muscle training (pressure load between −4 and −20 cmH2O)	Sham treatment with a resistive inspiratory muscle training device	Weaning period (Total study days: IG: 14.4 ± 8.1 days; CG: 18.0 ± 8.8 days)	This study reports about ICU patients on MV (mean age IG: 65.6 ± 11.7, CG: 65.1 ± 10.7; gender M/F: 16/19 in IG, 15/19 in CG). They were assessed on the first day of participation, every Monday and on days when the subjects attempted a 12-h aerosol tracheotomy collar (ATC) trial. The main finding is represented by the improvement observed in maximal inspiratory pressure (MIP) where the sham group’s pre- to post-training MIP change was not significant (−43.5 ± 17.8 vs. −45.1 ± 19.5 cm H2O, p = 0.39), while the IMT group’s MIP increased (−44.4 ± 18.4 vs. −54.1 ± 17.8 cm H2O, p < 0.0001). There were no adverse events observed during IMT or sham treatments. Twenty-five of 35 IMT subjects weaned (71, 95% confidence interval (CI) = 55 to 84%), while 16 of 34 (47, 95% CI = 31 to 63%) sham subjects weaned. The pre- and post-training MIP measures for the weaning success (n = 41) and failure (n = 28) groups were respectively (−44.0 ± 20.2 and −53.5 ± 20.7 cmH2O vs. −43.9 ± 14.8 and −43.9 ± 15.0 cmH2O). There was significant outcome × time interaction and the change in MIP for the successfully weaned group was significantly greater than the failure to wean group (p < 0.0001).
McCaughey et al. (38)	Critical Care	Australia	ICU patients on MV IG: n: 10 CG: n: 10	IG: Mean age: 56.5 ± 18.50 [median ± (IQR)]; Male/female: 7/3 CG: Mean age 61.0 ± 17.25 [median ± IQR)]; Male/female:5/5	Active abdominal FES training, 30 min, twice per day, 5 days per week. FES was set to a median of 60 mA, frequency of 30 Hz and a pulsewidth of 350 μs;	Sham abdominal FES training. FES was set to a median of 10 mA, frequency of 10 Hz and a pulsewidth of 350 μs.	Until ICU discharge (ICU length of stay) IG: not estimable; CG: 11 days;	This study reports about ICU patients on MV (mean IG: 56.5 (IQR 18.50), CG: 61.0 (IQR 17.25); gender M/F: 7/3 in IG, 5/5 in CG). They were assessed twice more in the first week of participation, and then weekly until ICU discharge. The main finding is represented by the improvement observed in ventilation duration (median 6.5 vs. 34 days, p = 0.039) and ICU length of stay (median 11 vs. not estimable days, p = 0.011) that were shorter in IG compared to the control group. However, no significant differences were underlined in terms of muscle thickness in rectus abdominis (p = 0.099 at day 3), diaphragm (p = 0.652 at day 3) or combined lateral abdominal muscles (p = 0.074 at day 3). The authors were unable to adequately assess MIP due to tracheostomy.
Pattanshetty and Gaude (39)	Indian J Crit Care Med	India	ICU patients on MV IG: n:50 CG: n:51	IG: Mean age: 47.8 ± 14.72; Male/female: 37/13 CG: Mean age: 51.6 ± 17.47; Male/female: 40/11	Positioning + chest wall vibrations + MH + suctioning MH: daily, twice a day, 20 min per session; Chest vibration: daily, twice a day, thrice in each zone (upper, middle, lower of chest); Suctioning: once every minute for 4 min, 15 s	MH + suctioning	Weaning period (MV: IG: 13.9 ± 9.77; CG: 11.3 ± 5.73)	This study reports about ICU patients on MV (mean age IG: 47.8 ± 14.72, CG: 51.6 ± 17.47; gender M/F: 37/13 in IG, 40/11 in CG). They were assessed after 48H from MV during the weaning period, before and after physiotherapy. The main finding is represented by the improvement observed in weaning of ventilation, successful in the case of 62% of the patients in the IG as compared to 31.37% of the patients in the CG, which was statistically significant (p = 0.007).
Pinkaew et al. (44)	Indian J Public Health Res Dev	Thailand	ICU and Sub-ICU patients on MV EMEB: n: 25 EM: n: 23 CG: n: 23	EMEB group: Mean age: 75.32 ± 14.28; Male/female: 7/18 EM group: Mean age: 69.08 ± 16.96; Male/female: 11/12 CG: Mean age: 74.68 ± 15.23; Male/female: 15/8	EMEB: Traditional therapy + EM protocol + elastic exercise in diagonal pull, shoulder flexion, flyer and reverse flyer postures, 10 times 3 sets, once a day, 5 times a week. The group took about 30 min to treat each time and provided treatment 5 days a week. EM: Traditional therapy + EM protocol (4 levels = level 1 is passive ROM; level 2 is passive ROM, active ROM, and sitting position minimum 20 min; level 3 is passive ROM, active ROM, sitting position minimum 20 min and sitting on edge of bed; level 4 is passive ROM, active ROM, sitting position minimum 20 min, sitting on edge of bed, active transfer to chair minimum 20 min)	Conventional physical therapy groups included passive and active ROM, breathing exercise, 5 times a week	Weaning period (MV time: EM: 5.78 ± 2.74 EMEB: 6.52 ± 4.40 CG: 12.82 ± 5.69)	This study reports about ICU patients on MV (mean age CG: 74.68 ± 15.23; EM: 69.08 ± 16.96; EMEB: 75.32 ± 14.28; 33 male and 38 female). They were assessed for all days of the protocol duration. The main finding is represented by the significant differences of MV duration (days) between the CG, the EM group and the EMEB group, that were 12.82 ± 5.69, 5.78 ± 2.74 (p < 0.05) and 6.52 ± 4.40 (p < 0.05), respectively. EMEB showed significantly increased handgrip strength changes compared to CG (IG: 3.53 ± 1.42 kgs; CG: 0.97 ± 1.21kgs; p < 0.05).
Sandoval Moreno et al. (40)	Med Intensiva	Colombia	ICU patients on MV IG: n: 62 CG: n: 64	IG: Mean age: 61 (range: 40–70); Male/female: 33/29 CG: Mean age: 62 (range: 47–72); Male/female: 38/26	Respiratory muscle training with threshold IMT, every day, twice a day for 3 series of 6–10 repetitions, with 2 min of rest between series.	standard care: respiratory physiotherapy, physical therapy, and MV management	Weaning period (MV time: IG:9.36 ± 12.51; CG: 8.78 ± 11.41)	This study reports about ICU patients on MV (mean age IG: 61 (range: 40–70), CG: 62 (range: 47–72); 53.23% male in IG, 59.38% male in CG). They were assessed after 48H from MV during the weaning period. There were no statistically significant differences in the median weaning time between the groups. There were no statistically significant differences in the median change in MIP between the groups (IG: 9.43 cmH2O vs. CG: 5.92 cmH2O; p = 0.48).
Taniguchi et al. (41)	Critical Care	Brazil	ICU patients on MV IG: n: 35 CG: n: 35	IG: Mean age: 66 ± 18; Male/female: 17/18 CG: Mean age: 62 ± 19; Male/female: 22/13	SmartCare device (the ventilator automatically adjusted pressure support at the minimum level while keeping the patient within a comfort zone)	Respiratory physiotherapy consisting of breathing spontaneously through PSV of 5–7 cmH2O and PEEP of 5 cmH2O, for a minimum of 30 min and a maximum of 2 h.	Weaning period (MV time: IG: 3.5 (2.0–7.3) CG: 4.1 (2.7–7.1)	This study reports about ICU patients on MV (mean age IG: 66 ± 18 (range: 20–93); CG: 62 ± 19 (range: 33–97); 49% male in IG, 63% male in CG). They were assessed during the weaning period. The main finding is represented by the improvement observed in weaning duration, which was shorter in the respiratory physiotherapy–driven weaning group (60 [50–80] min vs. 110 [80–130] min; p < 0.001). Total duration of MV (3.5 [2.0–7.3] days vs. 4.1 [2.7–7.1] days; p = 0.467) and extubation failure (2 vs. 2; p = 1.00) were similar between the two groups. No significant differences between groups were underlined in Tidal Volume.

Continuous variables are expressed as means ± SD, unless otherwise stated. CI, confidence interval; CG, control group; EM, early mobilization; EMEB, early mobilization with elastic band; ERCC, expiratory rib cage compression; FES, functional electrical stimulation; ICU, intensive care unit; IG, intervention group; IMT, inspiratory muscle training; IPPB, intermittent positive pressure breathing; IQR, interquartile range; MD, mean differences; MH, manual hyperinflation; MIP, maximal inspiratory pressure; MV, mechanical ventilation; PEEP, positive end-expiratory pressure; PSV, pressure support ventilation; ROM, range of motion; USA, United States of America.