A COMPUTER-MODEL OF GAS-EXCHANGE DURING CARDIOPULMONARY-RESUSCITATION

This paper presents a computer model of gas exchange during cardiopulm onary resuscitation (CPR) that permits independent adjustment of inspi red air content (16% O-2 and 4.5% CO2 present in mouth-to-mouth (MTM) ventilation or ambient air), shunt, deadspace, diffusion impairment, c ardiac output, and ventilation. The model contains 15500 acini, each w ith its own blood supply. Gas exchange occurs at each perfused and ven tilated acinus. Arterial P-O2 and P-CO2 are calculated from the summed arterial blood flow using standard formulae. The model and simulation s show that MTM ventilation provides inadequate oxygenation when the v ictim is at high altitude or has diffusion impairment. They also show that analysis of inspired and expired gas concentrations to measure ga s exchange primarily measures wash in and wash out of gas when cardiac output is low and that this explains the negative oxygen consumption and carbon dioxide production measured in a previous study. (C) 1998 E lsevier Science Ireland Ltd. All rights reserved.