BIPHASIC EXTRATHORACIC PRESSURE CPR - A HUMAN PILOT-STUDY

Hypothesis: Alternating intrathoracic pressure hv means of a chest cui rass can cause perfusion and ventilation equal to or better than stand ard cardiopulmonary resuscitation (CPR) for humans in cardiac arrest. Design: Nonrandomized, nonblinded, crossover pilot study. Setting: Lar ge urban emergency department. Subjects: Five adult normothermic, nont raumatic, out-of-hospital cardiac arrest patients unresponsive to stan dard advanced cardiac life support. Method: Right atrial and aortic ca theters mere inserted for pressure measurement and blood gas analysis while the patient was receiving standard CPR by a pneumatic compressio n device (Thumper). The Thumper was then replaced by a chest cuirass ( Hayek Oscillator). Pressure and blood gas measurements were then repea ted. Results: The coronary perfusion pressure increased from - 1.2+/-8 .6 mm Hg to 6.2+/-6.9 mm Hg for a mean change of 7.4+/-3.1 mm Hg (p = 0.006). The compression phase gradient increased 10.01+/-21.9 mm HE; ( p=0.364). The venous to arterial Pco(2) gradient decreased 44.5+/-32.3 mm Hg (p = 0.070). The oxygen extraction ratio increased 1.6+/-9.4 pe rcent (p=0.761). The mean arterial Po-2 and Pco(2) changed from 252 to 240 mm Hg (p=0.836) and from 53 to 66 (p =0.172) mm Hg, respectively. Conclusion: The Hayek Oscillator chest cuirass produced a significant improvement in the coronary perfusion pressure. There was a trend for improved systemic perfusion as indicated by an improved compression p hase gradient and venous to arterial Pco(2) gradient, although this wa s not supported by the lack of improvement in the oxygen extraction ra tio. The cuirass also adequately oxygenates and ventilates unassisted by positive pressure ventilation.