%0 Journal Article %A Richard H Kallet %A Michael S Lipnick %T END-TIDAL-TO-ARTERIAL PCO2 RATIO AS SIGNIFIER FOR PHYSIOLOGIC DEAD-SPACE RATIO AND OXYGENATION DYSFUNCTION IN ACUTE RESPIRATORY DISTRESS SYNDROME %D 2020 %R 10.4187/respcare.08061 %J Respiratory Care %P respcare.08061 %X Background: The ratio of end-tidal-to-arterial carbon dioxide tension (PETCO2/PaCO2) was recently suggested for monitoring pulmonary gas exchange in subjects with COVID-19 associated ARDS. Yet, no evidence was offered supporting that claim. Therefore, we evaluated whether PETCO2/PaCO2 might be relevant in assessing ARDS not associated with COVID-19.Methods: We evaluated the correspondence between PETCO2/PaCO2 and VD/VT measured in 561 subjects with ARDS from a previous study in whom PETCO2 data were also available. Subjects also were analyzed according to four categories representing increasing severity of PETCO2/PaCO2 (≥0.80, 0.61 to 0.79, 0.50-0.59 and < 0.50). Correlation was assessed by either Pearson Spearman tests, group comparisons were assessed using either ANOVA or Kruskal-Wallis tests, and dichotomous variables assessed by Fisher Exact test. Overall mortality risk was assessed by multivariate logistic regression. Alpha was set at 0.05.Results: PETCO2/PaCO2 correlated strongly with VD/VT (R = -0.87 [-0.89, -0.85] P < 0.001). Decreasing PETCO2/PaCO2 was associated with increased VD/VT and hospital mortality between all groups. In the univariate analysis for every 0.01 decrease in PETCO2/PaCO2 mortality risk increased by ∼1% (OR: 0.009 [0.003-0.029] P < 0.001), and maintained a strong independent association with mortality risk when adjusted for other variables: 0.19 (0.04-0.91) P = 0.039. PETCO2/PaCO2 < 0.50 was characterized both by very high VD/VT (0.82 ± 0.05, P < 0.001) and hospital mortality (70%).Conclusion: PETCO2/PaCO2 as a surrogate for VD/VT may be a useful and practical measurement for both management and ongoing research into the nature of ARDS. %U https://rc.rcjournal.com/content/respcare/early/2020/07/07/respcare.08061.full.pdf