[Ventilator-induced diaphragmatic dysfunction]

Evaluation of diaphragm ultrasound in predicting extubation outcome in mechanically ventilated patients with COPD

Background

To explore the value of the right hemi-diaphragmatic excursion (DE) and its variation in predicting extubation outcome in mechanically ventilated patients with COPD.

Methods

All included patients with COPD received mechanical ventilation (MV) and were ready to wean from MV. After patients passed the 30 min spontaneous breathing trail (SBT), extubation was considered to be feasible, and the right DE measured by ultrasound at 0 min, 5 min, and 30 min of SBT were named as DE₀, DE₅, and DE₃₀, respectively.

Results

Twenty-five patients succeeded extubation; 12 patients failed. The area under receiver operator characteristic curve (AUC_ROC) of DE₃₀ and ΔDE₃₀₋₅ (the variation between 30 and 5 min) were 0.762 and 0.835; a cutoff value of DE₃₀ > 1.72 cm and ΔDE₃₀₋₅ > 0.16 cm were associated with a successful extubation with a sensitivity of 76% and 84%, a specificity of 75% and 83.3%, respectively. The predictive probability equation of the DE₃₀ plus ∆DE₃₀₋₅ was P = 1/[1 + e^{−(−5.625+17.689×∆DE}₃₀₋₅^+1.802×DE₃₀⁾], a cutoff value of P > 0.626 was associated with a successful extubation with the AUC_ROC of 0.867, a sensitivity of 92%, and a specificity of 83.3%.

Conclusion

The combination of DE₃₀ and ∆DE₃₀₋₅ could improve the predictive value and could be used as the predictor of extubation outcome in mechanically ventilated patients with COPD.

Diaphragm Muscle Thinning in Subjects Receiving Mechanical Ventilation and Its Effect on Extubation

BACKGROUND

Diaphragm muscle weakness and atrophy are consequences of prolonged mechanical ventilation. Our purpose was to determine whether thickness of the diaphragm (TDI) changes over time after intubation and whether the degree of change affects clinical outcome.

METHODS

For this prospective, longitudinal observational study, we identified subjects who required mechanical ventilation and measured their TDI by ultrasonography. TDI was measured at baseline and repeated 72 h later and then weekly until the subject was either liberated from mechanical ventilation, was referred for tracheostomy, or died. The analysis was designed to determine whether baseline TDI and change in TDI affect extubation outcome.

RESULTS

Of the 57 subjects who underwent both diaphragm measurements at 72 h, 16 died, 33 were extubated, and 8 underwent tracheostomy. Only 14 subjects received mechanical ventilation for 1 week, and 2 subjects received mechanical ventilation for 2 and 3 weeks. Females had significantly thinner baseline TDI (P = .008). At 72 h, TDI had decreased in 84% of subjects. We found no significant association between the rate of thinning and sex (P = .68), diagnosis of COPD (P = .36), current smoking (P = .85), or pleural effusion (P = .83). Lower baseline TDI was associated with higher likelihood of extubation: 12.5% higher for every 0.01-cm decrease in TDI (hazard ratio 0.875, 95% CI 0.80-0.96, P = .003). For every 0.01-cm decrease in TDI at 72 h, the likelihood of extubation increased by 17% (hazard ratio 0.83, 95% CI 0.70-0.99, P = .041).

CONCLUSIONS

Although most of the subjects showed evidence of diaphragm thinning, we were unable to find a correlation with outcome of extubation failure. In fact, the thinner the diaphragm at baseline and the greater the extent of diaphragm thinning at 72 h, the greater the likelihood of extubation. Thickening ratio or other measurement may be a more reliable indicator of diaphragm dysfunction and should be explored.