title: Reliability of the arterial to end-tidal carbon dioxide gradient in mechanically ventilated patients with multisystem trauma.
abstract: The accuracy and reliability of the relationship between arterial and end-tidal carbon dioxide (PETCO2 and PaCO2), expressed as the gradient, P(a-ET)CO2, was assessed with 171 comparisons in nine mechanically ventilated trauma patients. The P(a-ET)CO2 was 14 +/- 11 mm Hg. (mean +/- standard deviation.) The positive correlation between PaCO2 (44 +/- 10 mm Hg) and PETCO2 (30 +/- 10 mm Hg) for the study population (reflected by r = 0.64, p = 0.001; but r2 = 0.41) indicated statistical significance, but only 40% of the changes reflected a linear relationship. Seventy-eight percent of individual patients had significant correlations of PaCO2 and PETCO2 (p < 0.02 to p < 0.001). Changes in PETCO2 erroneously predicted the PaCO2 changes in 27% of comparisons with 15% false decreases and 12% false increases. Trends in P(a - ET)CO2 magnitude are not reliable, and concordant direction changes in PETCO2 and PaCO2 are not assured.
authors.affiliation: Department of Anesthesia, Pennsylvania State University College of Medicine, Hershey.
authors.forename: G B
authors.initials: GB
authors.lastname: Russell
authors.forename: J M
authors.initials: JM
authors.lastname: Graybeal
mesh_terms: D000328:Adult; D001158:Arteries; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism*; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009104:Multiple Trauma / Q000378:metabolism* / Q000628:therapy; D010313:Partial Pressure; D015203:Reproducibility of Results; D012121:Respiration, Artificial
chemical_list: D002245:Carbon Dioxide