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Diaphragm dysfunction unable to predict extubation failure

New data show that ultrasound-detected diaphragmatic dysfunction does not predict which patients will fail to successfully wean from mechanical ventilation.

“Several studies have found that low excursion or weak diaphragm apposition thickening was strongly associated with weaning difficulties in patients who are mechanically ventilated, leading to prolonged mechanical ventilation. The most recent studies have even suggested that diaphragm ultrasound enabled the prediction of extubation outcome,” the researchers wrote in CHEST. “However, these studies were all performed in single centers with small patient samples, and ultrasound was not systematically applied just prior to extubation.”

This multicenter prospective study included 191 patients who were at high risk for reintubation, such as those older than 65 years, those with underlying cardiac or respiratory conditions and those who had been intubated for longer than 7 days. All patients successfully underwent a spontaneous breathing trial and diaphragmatic function was evaluated using ultrasound while breathing spontaneously on a T-piece.

During the 20-month study period, 33 patients failed extubation, including 22 patients who required early reintubation after developing severe acute respiratory failure within 48 hours after extubation, eight patients who required reintubation within the first 7 days after extubation and three patients who died without reintubation within the first 7 days due to a do-not-reintubate order. Hypoxia, inability to clear secretions, hypercapnia, upper airway obstruction, shock and altered consciousness status were the most common reasons for reintubation.

The researchers defined diaphragmatic dysfunction as bilateral diaphragmatic excursion less than 10 mm and apposition thickening less than 30%. The proportion of patients who were successfully weaned from mechanical ventilation was comparable to those in whom extubation failed when using both the excursion definition (46% vs. 51%; P = .55) and the thickening definition (71% vs. 68%; P = .73).

Furthermore, there were no significant differences in values of excursion and thickening at right or left between patients who were successfully extubated and those in whom extubation failed.

Physiotherapists also assessed patients’ cough strength in the study. For those with effective, moderate and ineffective cough, extubation failure rates were 7%, 22% and 46% (P < .01), respectively, with patients who failed extubation being less likely to have effective cough and more frequently having ICU-acquired weakness than those who were successfully extubated. Multivariate logistic regression analysis also identified effective cough as the only independent factor associated with successful extubation within 7 days (OR = 0.3; 95% CI, 0.14-0.67).

“Following the success of [a spontaneous breathing trial], assessment of diaphragm function by ultrasound prior to extubation did not enable prediction of extubation outcome in patients at high risk of reintubation in the ICU,” the researchers wrote. “By contrast, clinical assessment of cough strength was found to be a strong predictor of extubation failure.” – by Melissa Foster

Disclosures: This study was supported by a grant from the Association Lyonnaise de Logistique Post hospitalière. The authors report no relevant financial disclosures.