A COMPARISON OF THE END-TIDAL-CO2 DOCUMENTED BY CAPNOMETRY AND THE ARTERIAL PCO(2) IN EMERGENCY PATIENTS

Satisfactory artificial ventilation is defined as sufficient oxygenati on and normo- or slight arterial hypocarbia. Monitoring end tidal CO2 values with non-invasive capnometry is a routine procedure in anaesthe sia, emergency medicine and intensive care. In anaesthesia the ventila tion volume is adjusted to the capnometric end tidal CO2 (ETCO2), taki ng into account a normal variation from the pACO(2) of 3-8 mmHg. We ev aluated the usefulness and practicability of using ETCO2 for correctly adjusting ventilation parameters in prehospital emergency care, by co mparing arterial pCO(2) and ETCO2 of 27 intubated and ventilated patie nts. We used the side-stream capnometry module of the Defigard 2000 (B ruker, ChemoMedica Austria) and a portable blood gas analyzer (OPTI 1, AVL Graz, Austria). Evaluation of the group of patients as a whole sh owed that there was no correlation whatsoever between the end expirato ry and arterial CO2. Dividing the patients into three subgroups (I, Du ring CPR; II, respiratory disturbances of pulmonary and cardiac origin ; III, extrapulmonary respiratory disturbances), we found that only pa tients without primary cardiorespiratory damage showed a slight, but n ot statistically significant, correlation. This can be explained by th e fact that almost any degree of cardiorespiratory failure causes chan ges of the ventilation-perfusion ratio, impairing pulmonary CO2 elimin ation. We conclude, that the ventilation of emergency patients can onl y be correctly adjusted according to values derived from an arterial b lood gas analysis and ETCO2 measurements cannot be absolutely relied u pon for accuracy except, perhaps, in patients without primary cardiore spiratory dysfunction. (C) 1997 Elsevier Science Ireland Ltd.