title: Reducing ventilation frequency combined with an inspiratory impedance device improves CPR efficiency in swine model of cardiac arrest.
abstract: BACKGROUND
  The basic premise that frequent ventilations during cardiopulmonary resuscitation (CPR) are a necessity for tissue oxygenation has recently been challenged. An inspiratory impedance threshold device (ITD) recently has also been shown to increase CPR efficiency, principally by augmenting circulation with little impact on ventilation. The optimal compression to ventilation (C/V) is not known for this new device. The purpose of this study was to compare the currently recommended C/V ratio of 5:1 with a 10:1 ratio, +/- the ITD, to optimize circulation and oxygenation during CPR.
  
  
  METHODS
  Thirty-two adult pigs weighing 26-31 kg were randomized to CPR with varying C/V ratios +/- the ITD as follows: A = 5:1, B = 5:1+ITD, C = 10:1, D = 10:1+ITD. After 6 min of untreated ventricular fibrillation (VF), closed-chest standard CPR was performed with an automatic piston device that does not impede passive chest wall recoil, at a continuous compression rate of 100 min(-1). Synchronous breaths were given every 5 or 10 compressions during the decompression phase depending on the group. CPR was performed for 6 min and physiological variables were measured throughout the experimental protocol.
  
  
  RESULTS
  A reduction in the frequency of ventilation from 5:1 to 10:1 resulted in significantly improved arterial and coronary perfusion pressure in a pig model of cardiac arrest. Addition of an ITD resulted in further increases in arterial and coronary perfusion pressures with both 5:1 and 10:1 C/V ratios, without compromising oxygenation.
  
  
  CONCLUSIONS
  CPR efficiency can be optimized by changing the compression: ventilation ratio from 5:1 to 10:1 and with concurrent use of the inspiratory threshold device.
authors.affiliation: Department of Medicine, University of Minnesota (DY), Minneapolis, MN 55455, USA.
authors.forename: Demetris
authors.initials: D
authors.lastname: Yannopoulos
authors.forename: Gardar
authors.initials: G
authors.lastname: Sigurdsson
authors.forename: Scott
authors.initials: S
authors.lastname: McKnite
authors.forename: David
authors.initials: D
authors.lastname: Benditt
authors.forename: Keith G
authors.initials: KG
authors.lastname: Lurie
mesh_terms: D000818:Animals; D001775:Blood Circulation; D001794:Blood Pressure; D016887:Cardiopulmonary Resuscitation / Q000295:instrumentation* / Q000379:methods*; D003326:Coronary Circulation; D006323:Heart Arrest / Q000503:physiopathology* / Q000628:therapy*; D001239:Inhalation; D010100:Oxygen / Q000097:blood; D011312:Pressure; D012123:Pulmonary Ventilation; D012119:Respiration; D015656:Respiratory Mechanics; D013552:Swine
chemical_list: D010100:Oxygen