title: Basic life support with four different compression/ventilation ratios in a pig model: the need for ventilation.
abstract: BACKGROUND
  During cardiac arrest the paramount goal of basic life support (BLS) is the oxygenation of vital organs. Current recommendations are to combine chest compressions with ventilation in a fixed ratio of 30:2; however the optimum compression/ventilation ratio is still debatable. In our study we compared four different compression/ventilation ratios and documented their effects on the return of spontaneous circulation (ROSC), gas exchange, cerebral tissue oxygenation and haemodynamics in a pig model.
  
  
  METHODS
  Study was performed on 32 pigs under general anaesthesia with endotracheal intubation. Arterial and central venous lines were inserted. For continuous cerebral tissue oxygenation a Licox PtiO(2) probe was implanted. After 3 min of cardiac arrest (ventricular fibrillation) animals were randomized to a compression/ventilation-ratio 30:2, 100:5, 100:2 or compressions-only. Subsequently 10 min BLS, Advanced Life Support (ALS) was performed (100%O(2), 3 defibrillations, 1mg adrenaline i.v.). Data were analyzed with 2-factorial ANOVA.
  
  
  RESULTS
  ROSC was achieved in 4/8 (30:2), 5/8 (100:5), 2/8 (100:2) and 0/8 (compr-only) pigs. During BLS, PaCO(2) increased to 55 mm Hg (30:2), 68 mm Hg (100:5; p=0.0001), 66 mm Hg (100:2; p=0.002) and 72 mm Hg (compr-only; p<0.0001). PaO(2) decreased to 58 mmg (30:2), 40 mm Hg (100:5; p=0.15), 43 mm Hg (100:2; p=0.04) and 26 mm Hg (compr-only; p<0.0001). PtiO(2) baseline values were 12.7, 12.0, 11.1 and 10.0 mm Hg and decreased to 8.1 mm Hg (30:2), 4.1 mm Hg (100:5; p=0.08), 4.3 mm Hg (100:2; p=0.04), and 4.5 mm Hg (compr-only; p=0.69).
  
  
  CONCLUSIONS
  During BLS, a compression/ventilation-ratio of 100:5 seems to be equivalent to 30:2, while ratios of 100:2 or compressions-only detoriate peripheral arterial oxygenation and reduce the chance for ROSC.
authors: Department of Anaesthesiology and Critical Care, Philipps-University, D-35033 Marburg, Germany.
authors: Clemens
authors: C
authors: Kill
authors: Alexander
authors: A
authors: Torossian
authors: Christian
authors: C
authors: Freisburger
authors: Sebastian
authors: S
authors: Dworok
authors: Martin
authors: M
authors: Massmann
authors: Thorsten
authors: T
authors: Nohl
authors: Ronald
authors: R
authors: Henning
authors: Pascal
authors: P
authors: Wallot
authors: Andreas
authors: A
authors: Gockel
authors: Thorsten
authors: T
authors: Steinfeldt
authors: Jürgen
authors: J
authors: Graf
authors: Leopold
authors: L
authors: Eberhart
authors: Hinnerk
authors: H
authors: Wulf
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004867:Equipment Design; D006323:Heart Arrest / Q000503:physiopathology / Q000628:therapy*; D008021:Life Support Systems / Q000592:standards*; D010101:Oxygen Consumption / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012119:Respiration; D012121:Respiration, Artificial / Q000295:instrumentation*; D013552:Swine