title: Discriminating the effect of accelerated compression from accelerated decompression during high-impulse CPR in a porcine model of cardiac arrest.
abstract: OBJECTIVE
  Piston based mechanical chest compression devices deliver compressions and decompressions in an accelerated pattern, resulting in superior haemodynamics compared to manual compression in animal studies. The present animal study compares haemodynamics during two different hybrid compression patterns to a standard compression pattern resembling that of modern mechanical chest compression devices.
  
  
  METHODS
  In 12 anaesthetized domestic pigs in ventricular fibrillation, coronary perfusion pressures (CPP) and cerebral cortical blood flow (CCBF) was measured, and transesophageal echocardiography (TEE) was performed. Two hybrid compression patterns, one with accelerated trapezoid compression and slower sinusoid decompression (TrS), and one with slower sinusoid compression and accelerated trapezoid decompression (STr), were tested against a standard accelerated trapezoid compression-decompression pattern (TrTr) in a cross-over randomised setup.
  
  
  RESULTS
  There were 7% (1, 14, p=0.046) lower CCBF and 3 mmHg (1, 5, p=0.017) lower CPP with the TrS compared to TrTr pattern. No significant difference between STr and TrTr pattern in either CCBF, 6% (-3, 15, p=0.176) or CPP, 0 mmHg (-2, 3, p=0.703) was present. Our TEE recordings were insufficient for haemodynamic comparison between the different compression-decompression patterns. Despite standardized sternal piston position and placement of the pigs, TEE revealed varying degree of asymmetrical heart chamber compression in the animals.
  
  
  CONCLUSIONS
  Both cardiac and cerebral perfusion benefited from accelerated decompression, while accelerated compression did not improve haemodynamics. The evolution of mechanical CPR is dependent on further research on mechanisms generating forward blood flow during external chest compressions.
authors.affiliation: Institute for Experimental Medical Research and Centre for Heart Failure Research, Oslo University Hospital - Ullevål, Oslo, Norway. oystetom@medisin.uio.no
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Tømte
authors.forename: Ivar
authors.initials: I
authors.lastname: Sjaastad
authors.forename: Lars
authors.initials: L
authors.lastname: Wik
authors.forename: Artem
authors.initials: A
authors.lastname: Kuzovlev
authors.forename: Morten
authors.initials: M
authors.lastname: Eriksen
authors.forename: Per Andreas
authors.initials: PA
authors.lastname: Norseng
authors.forename: Kjetil
authors.initials: K
authors.lastname: Sunde
mesh_terms: D000818:Animals; D016887:Cardiopulmonary Resuscitation / Q000295:instrumentation / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003326:Coronary Circulation / Q000502:physiology*; D017548:Echocardiography, Transesophageal; D005260:Female; D006323:Heart Arrest / Q000628:therapy*; D013552:Swine