Impact of impedance threshold devices on cardiopulmonary resuscitation: a systematic review and meta-analysis of randomized controlled studies.

Abstract

Vital organ hypoperfusion significantly contributes to the dismal survival rates observed with manual cardiopulmonary resuscitation after cardiac arrest. The impedance threshold device is a valve which reduces air entry into lungs during chest recoil between chest compressions, producing a potentially beneficial decrease in intrathoracic pressure and thus increasing venous return to the heart. This review provides an update on the impedance threshold device and underlines its effect on short-term survival. MedCentral, CENTRAL, PubMed, and conference proceedings were searched (updated March 27, 2007). Authors and external experts were contacted. Three unblinded reviewers selected randomized trials using an impedance threshold device in cardiopulmonary resuscitation of nontraumatic out-of-hospital cardiac arrests. Four reviewers independently abstracted patient, treatment and outcome data. A total of 833 patients from five high quality randomized studies were included in the analysis. Pooled estimates showed that the impedance threshold device consistently and significantly improved return to spontaneous circulation (202/438 [46%] for impedance threshold device group vs. 159/445 [36%] for control, relative risk [RR] = 1.29 [1.10-1.51], p = .002), early survival (139/428 [32%] vs. 97/433 [22%], RR = 1.45 [1.16-1.80], p = .0009) and favorable neurologic outcome (39/307 [13%] vs. 18/293 [6%], RR = 2.35 [1.30-4.24], p = .004) with no effect on favorable neurologic outcome in survivors (39/60 [65%] vs. 18/44 [41%]) nor an improved survival at the longest available follow up (35/428 [8.2%] vs. 24/433 [5.5%]). This meta-analysis of randomized controlled studies suggests that the impedance threshold device improves early outcome in patients with out-of-hospital cardiac arrest undergoing cardiopulmonary resuscitation.