title: Mechanical chest compressions with trapezoidal waveform improve haemodynamics during cardiac arrest.
abstract: BACKGROUND
  During manual chest compressions for cardiac arrest the waveforms of chest compressions are generally sinusoidal, whereas mechanical chest compression devices can have different waveforms, including trapezoidal. We studied the haemodynamic differences of such waveforms in a porcine model of cardiac arrest.
  
  
  METHODS
  Eight domestic pigs (weight 31±3kg) were anaesthetised and instrumented to continuously monitor aortic (AP) and right atrial pressure (RAP), carotid (CF) and cerebral cortical microcirculation blood flow (CCF). Coronary perfusion pressure (CPP) was calculated as the maximal difference between AP and RAP during diastole or decompression phase. After 4 min of electrically induced ventricular fibrillation, mechanical chest compressions were performed with four different waveforms in a factorial design, and in randomized sequence for 3 min each. Resulting differences are presented as mean with 95% confidence intervals.
  
  
  RESULTS
  Mean AP and RAP were higher with trapezoid than sinusoid chest compressions, difference 5.7 (0.7, 11) and 6.3 (2.1, 11)mmHg, respectively. Flow measured as CF and CCF was also improved with trapezoidal waveform, difference 14 (2.8, 26)ml/min and 11 (5.6, 17)% of baseline, respectively, with a parallel, non-significant (P=0.08) trend for CPP. Active vs. passive decompression to zero level improved CF, but without even a trend for CPP.
  
  
  CONCLUSIONS
  Trapezoid chest compressions and active decompression to zero level improved blood flow to the brain. The compression waveform is an additional factor to consider when comparing mechanical and manual chest compressions and when comparing different compression devices.
authors.affiliation: Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway. jo.kramer-johansen@medisin.uio.no
authors.forename: Jo
authors.initials: J
authors.lastname: Kramer-Johansen
authors.forename: Morten
authors.initials: M
authors.lastname: Pytte
authors.forename: Ann-Elin
authors.initials: AE
authors.lastname: Tomlinson
authors.forename: Kjetil
authors.initials: K
authors.lastname: Sunde
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Dorph
authors.forename: Jan Vegard H
authors.initials: JV
authors.lastname: Svendsen
authors.forename: Morten
authors.initials: M
authors.lastname: Eriksen
authors.forename: Tævje A
authors.initials: TA
authors.lastname: Strømme
authors.forename: Lars
authors.initials: L
authors.lastname: Wik
mesh_terms: D000818:Animals; D035641:Chest Wall Oscillation; D006323:Heart Arrest / Q000503:physiopathology* / Q000628:therapy*; D013552:Swine