Arterial blood-gases with 500-versus 1000-ml tidal volumes during out-of-hospital CPR

The correct tidal volume during cardiopulmonary resuscitation (CPR) is pres ently debated. While the European Resuscitation Council (ERC) and American Heart Association (AHA) previously recommended a tidal volume of 800-1200 m l, the ERC has recently reduced this to 400-600 ml. In a prospective, rando mised study of 17 non-traumatic out-of-hospital cardiac arrest patients int ubated and mechanically ventilated 12 min(-1) with 100% oxygen, we have the refore compared arterial blood gases generated with tidal volumes of 500 an d 1000 ml. Mean time from cardiac arrest to arrival of the ambulance was 13 +/- 8 and 14 +/- 8 min in the two groups, respectively. Arterial blood sam ples were taken percutaneously 5 and 10-15 min after onset of the mechanica l ventilation and analysed instantly. Pa-CO2 was significantly higher for a tidal volume of 500 than 1000 ml at both 5 and 10-15 min, 7.48 +/- 2.23 ve rsus 3.70 +/- 0.83 kPa (P = 0.002) and 7.45 +/- 1.19 versus 3.98 +/- 1.58 k Pa (P < 0.001). The pH was lower for 500 than 1000 ml at 10-15 min, 7.01 +/ - 0.10 versus 7.20 +/- 0.17 (P = 0.034), with a strong trend in the same di rection at 5 min (P = 0.06). There was adequate oxygenation with no differe nces in Pa-O2 or BE at any time between the two groups, and no significant differences in any blood gas variables between the 5- and 10-15-min samples . We conclude that arterial normocapnia is not achieved with either tidal v olume during advanced life support with non-rebreathing ventilation at 12 m in(-1). What ventilation volume is required for CO2 removal and oxygenation during basic life support with mouth-to-mouth ventilation cannot be extrap olated from the present data. In that situation the risk of gastric inflati on, regurgitation and aspiration must also be taken into account. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.