title: Arterial blood-gases with 500- versus 1000-ml tidal volumes during out-of-hospital CPR.
abstract: The correct tidal volume during cardiopulmonary resuscitation (CPR) is presently debated. While the European Resuscitation Council (ERC) and American Heart Association (AHA) previously recommended a tidal volume of 800-1200 ml, the ERC has recently reduced this to 400-600 ml. In a prospective, randomised study of 17 non-traumatic out-of-hospital cardiac arrest patients intubated and mechanically ventilated 12 min(-1) with 100% oxygen, we have therefore compared arterial blood gases generated with tidal volumes of 500 and 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 samples were taken percutaneously 5 and 10-15 min after onset of the mechanical ventilation and analysed instantly. Pa(CO(2)) was significantly higher for a tidal volume of 500 than 1000 ml at both 5 and 10-15 min, 7.48+/-2.23 versus 3.70+/-0.83 kPa (P=0.002) and 7. 45+/-1.19 versus 3.98+/-1.58 kPa (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 direction at 5 min (P=0.06). There was adequate oxygenation with no differences in Pa(O(2)) 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 volume during advanced life support with non-rebreathing ventilation at 12 min(-1). What ventilation volume is required for CO(2) removal and oxygenation during basic life support with mouth-to-mouth ventilation cannot be extrapolated from the present data. In that situation the risk of gastric inflation, regurgitation and aspiration must also be taken into account.
authors.affiliation: Institute for Experimental Medical Research and Norwegian Air Ambulance, Ulleval University Hospital, Oslo, Norway. audun.langhelle@ioks.uio.no
authors.forename: A
authors.initials: A
authors.lastname: Langhelle
authors.forename: K
authors.initials: K
authors.lastname: Sunde
authors.forename: L
authors.initials: L
authors.lastname: Wik
authors.forename: P A
authors.initials: PA
authors.lastname: Steen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016887:Cardiopulmonary Resuscitation / Q000379:methods* / Q000706:statistics & numerical data; D004632:Emergency Medical Services; D005260:Female; D006323:Heart Arrest / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D011446:Prospective Studies; D012123:Pulmonary Ventilation; D012307:Risk Factors; D013990:Tidal Volume / Q000502:physiology*; D013997:Time Factors
chemical_list: D010100:Oxygen