Association of Diaphragm Movement During Cough, as Assessed by Ultrasonography, With Extubation Outcome

A cough peak flow (CPF) of < 60 L/min was associated with increased risk of extubation failure after a successful spontaneous breathing trial (SBT). Passive cephalic excursion of the diaphragm (PCED), measured by ultrasonography during cough expiration, was reported to predict CPF in healthy adults. We hypothesized that PCED, diaphragm peak velocity, or both during cough, as measured by ultrasonography, might predict CPF and extubation outcomes in mechanically ventilated patients. This study attempted to identify associations of diaphragm movement during cough, as assessed by ultrasonography with simultaneously measured CPF, and to determine predictive values of ultrasonographic indices for extubation outcomes after a successful SBT.

In the study, 252 mechanically ventilated subjects with a successful SBT were enrolled in a prospective cohort study. Right hemidiaphragm passive cephalic excursion and peak velocity were measured by ultrasonography during voluntary cough expiration with maximum effort. CPF was measured simultaneously by ultrasonography.

A multiple regression model adjusted for age and sex showed a significant association between PCED and CPF (P < .001, adjusted β coefficient 11.4, 95% CI 8.88-14.0, adjusted R² = 0.287) and between diaphragm peak velocity and CPF (P < .001, adjusted β coefficient 1.71, 95% CI 1.91-2.24, adjusted R² = 0.235). The areas under the curves of PCED, diaphragm peak velocity, and CPF for extubation failure were 0.791 (95% Cl 0.668-0.914), 0.587 (95% Cl 0.426-0.748), and 0.765 (95% Cl 0.609-0.922), respectively.

PCED on ultrasonography was significantly associated with CPF and extubation failure after a successful SBT. Future studies should investigate if this method is applicable for determination of tracheostomy decannulation in stable patients in general wards.