Oxygen delivery and return of spontaneous circulation with ventilation:compression ratio 2:30 versus chest compressions only CPR in pigs

The need for rescue breathing during the initial management of sudden cardiac arrest is currently being debated and reevaluated. The present study was designed to compare cerebral oxygen delivery during basic life support (BLS) by chest compressions only with chest compressions plus ventilation in pigs with an obstructed airway mimicked by a valve hindering passive inhalation. Resuscitability was then studied during the subsequent advanced life support (ALS) period. After 3 min of untreated ventricular fibrillation (VF) BLS was started. The animals were randomised into two groups. One group received chest compressions only. The other group received ventilations and chest compressions with a ratio of 2:30. A gas mixture of 17% oxygen and 4% carbon dioxide was used for ventilation during BLS. After 10 min of BLS, ALS was provided. All six pigs ventilated during BLS attained a return of spontaneous circulation (ROSC) within the first 2 min of advanced cardiopulmonary resuscitation (CPR) compared with only one of six compressions-only pigs. While all except one compressions-only animal achieved ROSC before the experiment was terminated, the median time to ROSC was shorter in the ventilated group. With a ventilation:compression ratio of 2:30 the arterial oxygen content stayed at 2/3 of normal, but with compressions-only, the arterial blood was virtually desaturated with no arterio-venous oxygen difference within 1.5–2 min. Haemodynamic data did not differ between the groups. In this model of very ideal BLS, ventilation improved arterial oxygenation and the median time to ROSC was shorter. We believe that in cardiac arrest with an obstructed airway, pulmonary ventilation should still be strongly recommended. A necessidade de insuflações de emergência durante a fase inicial da abordagem da paragem cardı́aca súbita está actualmente em debate e a ser reavaliada. Este estudo foi desenhado para comparar o fornecimento cerebral de oxigénio durante o suporte básico de vida (BLS) só com compressões torácicas e com compressões torácicas e insuflações, em porcos com a via aérea obstruı́da através de uma válvula. A reanimabilidade era depois estudada no perı́odo subsequente de suporte avançado de vida (ALS). Após 3 minutos de fibrilhação ventricular iniciava-se BLS. Os animais eram distribuı́dos aleatoriamente em dois grupos. Um, recebia apenas compressões torácicas. O outro recebia ventilações e compressões à razão de 2:30. Usou-se uma mistura gasosa de 17% de oxigénio e