Main characteristics of the studies included in the systematic review
| Study | N (% male) | Age (year) | Study design | Patient category | Inclusion criteria | Duration of MV (day) | DD measurements | Definition of weaning failure | Outcomes |
| Jiang et al 19 | 27 (49) | 67 (33–84) | Prospective cohort | Medical ICU patients | Received MV and prepared for extubation after SBT | 11±6 | Displacement of the liver/spleen | Reintubation or NIMV within 72 hours | Mean values of liver and spleen displacements (mm) were higher in the SG than the FG (14.5±4.8 vs 8.4±3.9, p<0.001) |
| Kim et al 11 | 50 (61) | 66 | Prospective cohort | Medical ICU patients | MV for 48 hours and passed SBT | Non-DD, 8.4 (4.5–17) DD, 24 (15.5–35.4) | DE (mm) | MV within 48 hours of self-breathing | Patients with DD had higher rates of primary (20 of 24 vs 34 of 58, p<0.01) and secondary weaning failures (10 of 20 vs 10 of 46, p<0.01) |
| DiNino et al 35 | 63 (49) | 66±19 | Prospective cohort | Medical ICU patients | MV patients as ready to undergo a weaning trial or SBT | 5 (IQR4) | DT | Reintubation within 48 hours or terminal extubation or tracheostomy | The combined sensitivity and specificity of Δtdi% ≥30% for extubation success was 88% and 71%, respectively |
| Ferrari et al 30 | 34 (74) | 54.6±12.1 | Prospective cohort | MV patients received tracheostomy in a high- dependency unit | Received MV and underwent SBT | 28 (22–37) | DT | SBT failure | DTF (%) was significantly different between the SG and the FG (56 (38–64) vs 26 (22–30), p<0.0001) |
| Ali and Mohamad 12 | 45 (75) | 54±11.23 | Prospective cohort | Mixed ICU patients | Patients had a likelihood of prolonged (>72 hours) MV | 8±13.22 | DE and DT | MV within 48 hours of self-breathing | SG presented higher DE (23 (19–28) vs 12 (9–14)), p<0.0001 and DTF (56 (35–63) vs 26 (22–33), p<0.0001) |
| Dres et al 13 | 52 (68) | 57±16 | Prospective cohort | Medical ICU patients | MV for at least 24 hours and underwent SBT | 4 (2–6) | DE and DT | SBT failure | SG presented higher DE (11.2±3.7 vs 8.2±4.2), p=0.01 and DTF (35±12 vs 19±9, p<0.001) |
| Gong and Zhang 27 | 32 (73) | 67.59±9.78 | Prospective cohort | Mixed ICU patients | MV for at least 24 hours and passed SBT | SG (5.27±2.64) FG (6.64±2.68) | DE | SBT failure or the need for reintubation, or NIMV or death within 48 hours | No significant difference of DE between SG and FG (15.8±5.2 vs 18.4±10.2, p>0.05) |
| Hu et al 20 | 34 (67) | SG (59.2±12.5) FG (61.5±13.9) | Prospective cohort | Medical ICU patients | MV for at least 48 hours | SG, 4 (3.5) FG, 8 (7.8) | DE and DT | Not specified | SG presented higher DE (17±6 vs 10±4, p<0.01) and DTF (32±22 vs 20±5, p=0.04) |
| Spadaro et al 21 | 31 (61) | 65±13 | Prospective cohort | Mixed ICU patients | MV for at least 48 hours at their first SBT | 69 (53–173) | DE | SBT failure, reintubation, or NIMV within 48 hours | SG presented higher DE (15.5 (11.7–23.0) vs 7.0 (6.0–14.7), p<0.0001) |
| Farghaly and Hasan22 | 31 (57) | SG, 65 (55–67.8) FG, 62.5 (55–70.7) | Prospective cohort | Respiratory ICU patients | Received MV and passed SBT | SG, 5 (4–5.7) FG, 5 (4–5.3) | DE and DT | Inability to maintain spontaneous breathing without any ventilatory support within 48 hours | SG presented higher DE (16 (11.4–18) vs 9.8 (8.8–12), p<0.0001) and DTF (58.9 (38–84.3) vs 30.8 (22.3–85), p=0.021) |
| Xu et al 23 | 37 (60) | SG (71.2±8.3), FG (73.1±7.4) | Retrospective cohort | Respiratory ICU patients | COPD patients Received MV and underwent SBT | SG (10.2±3.2), FG (14.5±4.6) | DE | SBT failure, reintubation or NIMV within 48 hours | SG presented higher DE (12.6±3.4 vs 9.6±1.1, p<0.05) |
COPD, chronic obstructive pulmonary disease; DD, diaphragmatic dysfunction; DE, diaphragmatic excursion; DT, diaphragm thickness; DTF, diaphragmatic thickening fraction; FG, failure group; ICU, intensive care unit; MV, mechanical ventilation; NIMV, non-invasive mechanical ventilation; SBT, spontaneous breathing trial; SG, success group.