Table 2 Recent literature on predictive value of DUS

Diaphragm excursion (DE)

Jiang et al. [61]

Mean values of liver and spleen displacement during SBTs were higher in the successfully weaned group. Sensitivity and specificity for predicting successful extubation were 84.4% and 82.6%, respectively

Spadaro et al. [62]

By replacing tidal volume (VTe) with DE in the formula for the Rapid Shallow Breathing Index (RSBI = RR/VTe), the authors created a new index called the diaphragmatic-RSBI (D-RSBI)

The use of diaphragmatic excursion makes this index more accurate than the traditional rapid shallow breathing index in predicting outcome from weaning

Kim et al. [43]

The authors describe an association between diaphragmatic dysfunction (DE < 10 mm obtained by M-Mode ultrasonography), a prolonged weaning period, and early or delayed weaning failures

Luo et al. [63]

The authors find that a DE cut-off value < 12.6 mm was the most reliable predictor of reintubation within 1 week (sensitivity 80%, negative specificity 68.4%)

Garrido-Aguirre et al. [64]

The authors propose a new weaning index (ULDIMex) that takes into consideration inspiration time (a), expiration time (b), and DE (c). With the conceived formula (a + b)c/2, the authors identified a cut-off slope value of 4.06 cm/s for ULDIMex in successfully weaned patients, with a negative predictive value of 96.5%

Palkar et al. [65]

Greater diaphragm excursion, a longer inspiratory time, and a smaller decrease in the diaphragmatic excursion-time (E-T) index during SBT may help to predict successful extubation

Carrie et al. [66]

According to the authors, DE was unable by itself to predict weaning failure with low sensitivity and specificity 59% and 71%, respectively

Diaphragm thickening fraction (DTF)

Jung et al. [67]

The authors reveal a significantly lower mean DTF in patients requiring reintubation versus patients who did not (12% vs. 20%, p = 0.008)

Samanta et al. [68]

DTF assessment of the right diaphragm during pressure support ventilation (PSV) may be employed to predict successful weaning prior to a T-piece SBT

Blumhof et al. [69]

A DTF > 20% is a robust predictor of extubation success during pressure support ventilation tests with 5/5 and 10/5 cmH₂O with sensitivity and specificity values of 84.6% and 79.0%, 88.9% and 75.0%, respectively

DiNino et al. [70]

The authors find that a DTF threshold > 30% at end inspiration has a positive predictive value of 91% and a negative predictive value of 63% for extubation success (sensitivity 88% and specificity 91%, respectively), with similar results during both SBT and pressure support tests

Diaphragm excursion (DE) and diaphragm thickening fraction (DTF)

Farghaly et al. [71]

The authors found that cut-off values of DE ≥ 10.5 mm, Te-insp ≥ 21 mm, and DTF > 34.2% during SBT with pressure support were associated with successful weaning; combining a DE ≥ 10.5 mm with a Te-insp. ≥ 21 mm decreased the sensitivity to 64.9%, but increased specificity up to 100% for successful weaning

Zambon et al. [72]

The authors describe both DE and DTF to be useful weaning predictors, but only DTF is shown to be an accurate index of diaphragmatic contractility workload

Llamas-Alvarez et al. [73]

This systematic review and metanalysis concludes that diaphragm ultrasound measures (DTF > DE) can help predict weaning outcome. It also suggests that the accuracy of DTF and DE may be overestimated in the current literature depending on the patient subpopulation studied

Vivier et al. [53]

The authors conducted a multicenter prospective study involving 191 patients where DTF and DE data were collected during T-piece SBTs. They found that diaphragmatic dysfunction as assessed by ultrasound (described as DE < 10 mm and DTF < 30%) was not associated with extubation failure