Abstract
BackgroundA spontaneous breathing trial (SBT) is a major diagnostic tool to predict successfully extubation in patients. Several factors may lead to weaning failure, including the degree of lung aeration loss and diaphragm dysfunction. The main objective was to compare the diaphragmatic contractility between patients with high lung aeration loss and low lung aeration loss during a 30-minute SBT by ultrasound.MethodsThis was a prospective single-center study. Lung ultrasound aeration score (LUS) and diaphragmatic thickening fraction (DTF) were measured during mechanical ventilation 1 h before SBT (T-1), 30 min (T1), and 120 min (T2) after the start of the SBT during quiet breathing. The right and left DTF were compared between patients with LUS ≥ 14 (high lung aeration loss), considered at high risk of post-extubation distress, and those with LUS < 14 (low lung aeration loss). The relationship between the LUS and DTF and the changes in LUS and DTF from T-1 to T2 in patients with LUS ≥ 14 were assessed.ResultsForty-nine patients were analyzed; 33 had LUS ≥ 14 and 16 had LUS < 14 at T1. The DTF at T1 was significantly higher in patients with LUS ≥ 14 than in those with LUS < 14: the right median (IQR) DTF was 22.2% (17.1 to 30.9%) vs. 14.8% (10.2 to 27.0%) (p = 0.035), and the left median (IQR) DTF was 25.0% (18.4 to 35.0%) vs. 18.6% (9.7 to 24.2%) (p = 0.017), respectively. There was a moderate positive correlation between the LUS and the DTF (Rho = 0.3, p = 0.014). A significant increase in the LUS was observed from T-1 to T1, whereas no change was found between T1 and T2. The DTF remained stable from T-1 to T2.ConclusionsDuring a SBT, diaphragmatic contraction acts differently depending on the degree of pulmonary aeration. In patients with high lung aeration loss, increased diaphragmatic contractility indicates an additional respiratory effort to compensate lung volume loss that would contribute to successful SBT. Further studies are needed to evaluate the combined evaluation of lung aeration and diaphragmatic function to predict the successful weaning of patients from mechanical ventilation.
Highlights
A spontaneous breathing trial (SBT) is a major diagnostic tool to predict successfully extubation in patients
The loss of lung aeration at the end of a SBT assessed by ultrasonography was significantly greater in patients who developed postextubation distress than in those who were definitively weaned from mechanical ventilation [4]
Lung aeration and diaphragmatic thickening fraction (DTF) changes from T-1 to 120 min after the start of SBT (T2) in patients with lung aeration ultrasound score (LUS) ≥ 14 Of the 33 patients with LUS ≥ 14 who successfully passed the 30-min SBT, 1 patient failed after 120 min of Discussion The results of this study showed that, after achieving 30 min of SBT, the diaphragmatic contractility estimated by the DTF was significantly higher in patients with high lung aeration loss, defined as a LUS ≥ 14, than in patients with low lung aeration loss (LUS < 14)
Summary
A spontaneous breathing trial (SBT) is a major diagnostic tool to predict successfully extubation in patients. A spontaneous breathing trial (SBT) is a major diagnostic tool to determine whether patients can be successfully extubated [1, 2]. A number of factors may be responsible for the failure of a SBT and/or post-extubation distress, such as cardiovascular diseases, lung aeration loss [3,4,5], and dysfunction of the respiratory muscles, including diaphragmatic dysfunction [6, 7]. The loss of lung aeration at the end of a SBT assessed by ultrasonography was significantly greater in patients who developed postextubation distress than in those who were definitively weaned from mechanical ventilation [4]. In patients with prolonged mechanical ventilation, it has been shown that the diaphragmatic thickening fraction (DTF), defined as the diaphragmatic thickness at end-inspiration (TEI) minus the diaphragmatic thickness at end-expiration (TEE) divided by the TEE, was significantly lower in patients who failed the SBT than in patients who had a successful SBT [9]
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