title: An updated systematic review and meta-analysis on impedance threshold devices in patients undergoing cardiopulmonary resuscitation.
abstract: BACKGROUND
  Uncertainty persists on the clinical impact of impedance threshold devices in out-of-hospital cardiac arrest. We conducted an updated systematic review on impedance threshold devices.
  
  
  METHODS
  Several databases were searched for studies testing the effectiveness of impedance threshold devices in patients with cardiac arrest. The primary endpoint was long-term survival.
  
  
  RESULTS
  Seven trials (11,254 patients) were included. In 4 studies (2,284 patients) impedance threshold devices were used with active compression-decompression-cardiopulmonary resuscitation, and in the others alone. Overall, impedance threshold devices did not impact on the rate of return of spontaneous circulation (odds ratio=1.17 [0.96-1.43], p=0.114), favorable neurologic outcome (odds ratio=1.56 [0.97-2.50], p=0.065), or long-term survival (odds ratio=1.22 [0.94-1.58], p=0.127). These analyses were fraught with heterogeneity (respectively, p=0.055, p=0.236, and p=0.011) and inconsistency (respectively, I-squared=51% , I-squared=27% , and I-squared=67%). Exploratory analysis showed that combined use of impedance threshold devices with active compression-decompression significantly increased the likelihood of return of spontaneous circulation (odds ratio=1.19 [1.00-1.40], p=0.045), favorable neurologic outcome (odds ratio=1.60 [1.14-2.25], p=0.006), and long-term survival (odds ratio=1.52 [1.11-2.08], p=0.009). The favorable impact of the interaction between impedance threshold devices and active compression-decompression was also confirmed at meta-regression analysis (respectively, b=0.195 [0.004-0.387], p=0.045, b=0.500 [0.079-0.841], p=0.018, b=0.413 [0.063-0.764], p=0.021).
  
  
  CONCLUSIONS
  The evidence base on impedance threshold devices is apparently inconclusive, with a neutral impact on clinically relevant outcomes. However, exploratory analysis focusing on the combined use of impedance threshold devices with active compression-decompression suggests that this combo treatment may be useful to improve patient prognosis.
authors.affiliation: Department of Medico-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Latina, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Biondi-Zoccai
authors.affiliation: VCU Pauley Heart Center, Richmond, VA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Abbate
authors.affiliation: Department of Anesthesia and Intensive Care, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Landoni
authors.affiliation: Department of Anesthesia and Intensive Care, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Zangrillo
authors.affiliation: Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: J L
authors.initials: JL
authors.lastname: Vincent
authors.affiliation: Division of Cardiology, Department of Internal Medicine, University of Turin, Città della Salute e della Scienza, Turin, Italy.
authors.forename: F
authors.initials: F
authors.lastname: D'Ascenzo
authors.affiliation: Department of Medico-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Latina, Italy ; Department of AngioCardioNeurology, IRCCS Neuromed, Pozzilli, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Frati
keywords: active compression-decompression; cardiopulmonary resuscitation; impedance threshold device; return of spontaneous circulation