Utility of the dead space fraction (Vd/Vt) as a predictor of extubation success

• Published in: Medicina intensiva (English ed.) 2011-12, Vol.35 (9), p.529-538
• Main Authors: González-Castro, A, Suárez-Lopez, V, Gómez-Marcos, V, González-Fernandez, C, Iglesias-Posadilla, D, Burón-Mediavilla, J, Rodríguez-Borregan, J.C, Miñambres, E, Llorca, J
• Format: Article
• Language: English
• Subjects: Critical Care; Internal Medicine
• ISSN: 2173-5727; 2173-5727
• DOI: 10.1016/j.medine.2012.01.002

Abstract Purpose To determine the value of V d/ V t as a predictor of extubation failure in patients with mechanical ventilation admitted to the intensive care units. Design A prospective, observational cohort study conducted from 1 September 2010 to 1 March 2011. Setting General intensive care unit (G-ICU) of a third level university hospital. Patients or participants The study included patients on mechanical ventilation (MV) for over 12 h, and who in the process of weaning were subjected to low-level pressure support. Exclusion criteria were age under 18 years, ventilation via tracheotomy and patients failing to cooperate for different reasons. During the study, 392 patients were admitted to the G-ICU; of these, 214 required MV. The weaning process was started in 154 cases. Fifty-four patients were excluded from the study, and 24 were not extubated from MV. A total of 76 patients were finally extubated and analyzed. Variables of interest V d/ V t was calculated as the ratio ( P aCO2 − P eCO2 )/ P aCO2 , with the recorded parameters. Results Logistic regression analysis showed a significant association between the V d/ V t and extubation failure, with OR = 1.52 (95%CI 1.11–2.09, p = 0.008). The area under the ROC curve with respect to the prediction of extubation failure according to the V d/ V t value was 0.94 (95%CI 0.86–0.98, p < 0.0001). Conclusions V d/ V t is a powerful predictor of extubation failure in patients on MV.