title: Effects of an impedance threshold device on hemodynamics and restoration of spontaneous circulation in prolonged porcine ventricular fibrillation.
abstract: BACKGROUND
  An impedance threshold device (ITD) has been designed to enhance circulation during CPR by creating a negative intrathoracic pressure during the relaxation phase of chest compression.
  
  
  OBJECTIVE
  We sought to determine the effects of the ITD on coronary perfusion pressure (CPP), return of spontaneous circulation (ROSC), and short-term survival (20 minutes after ROSC). We hypothesized that the ITD would improve all 3 variables when compared to standard CPR.
  
  
  METHODS
  Using a case-control design nested within a randomized primary study, we compared CPR with the ITD (ITD-CPR) to standard CPR without the device (S-CPR). We systematically assigned 36 domestic swine, weighing 23-29 kg, (18 per group) to resuscitation with either ITD-CPR or S-CPR after 8 minutes of untreated ventricular fibrillation (VF). At minute 8, mechanical chest compression and ventilation began, and drugs (0.1 mg/kg epinephrine, 40U vasopressin, 1.0 mg propranolol, 1 mEq/kg sodium bicarbonate) were given. The first rescue shock (150J biphasic) was delivered at minute 11 of VF. We recorded CPP, ROSC (systolic pressure > 80 mmHg sustained for 60 s continuously), and survival. Data were analyzed with Fisher's exact test and generalized estimating equations (GEE), with alpha = 0.05.
  
  
  RESULTS
  We analyzed 3,150 compressions. CPP for the ITD-CPR group (28.1 mmHg [95% CI 27-29.3 mmHg]), did not differ from the S-CPR group (32.3 mmHg [95% CI 31.2-33.4 mmHg]). ROSC occurred in 6/18 (33%) animals in the ITD-CPR, and 14/18 (78%) in the S-CPR group (p = 0.02). Survival occurred in 3/18 (17%) ITD-CPR and 13/18 (72%) S-CPR group (p = 0.003).
  
  
  CONCLUSIONS
  ITD-CPR did not improve CPP compared to S-CPR. ROSC and survival were significantly lower with ITD-CPR.
authors: Department of Emergency Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA. menegazz+@pitt.edu
authors: James J
authors: JJ
authors: Menegazzi
authors: David D
authors: DD
authors: Salcido
authors: Michael T
authors: MT
authors: Menegazzi
authors: Jon C
authors: JC
authors: Rittenberger
authors: Brian P
authors: BP
authors: Suffoletto
authors: Eric S
authors: ES
authors: Logue
authors: Timothy J
authors: TJ
authors: Mader
mesh_terms: D000818:Animals; D016887:Cardiopulmonary Resuscitation / Q000295:instrumentation*; D003326:Coronary Circulation / Q000502:physiology*; D005260:Female; D006323:Heart Arrest / Q000628:therapy; D008297:Male; D011446:Prospective Studies; D012039:Regional Blood Flow; D013552:Swine / Q000097:blood*; D015919:Ventilators, Negative-Pressure; D014693:Ventricular Fibrillation / Q000628:therapy*