Matt Harmon

159 Chapter eight performance, CPC 2 moderate cerebral disability, independent in activities of daily life, CPC 3 severe cerebral disability, dependent on others for daily support, 4 vegetative state and CPC 5 dead). 26-28 The CPC-scale was dichotomized to good (CPC 1 – 2) and poor (CPC 3 – 5) outcome. 29 In a secondary analysis we used the biomarker protein Tau as outcome to strengthen the analyses using neurologic functional outcome. 1. Main analysis Levels of carbon dioxide As our main analysis, we studied the association of dyscarbia with neurological outcome by dividing the cohort into three groups according to the single highest or lowest PaCO 2 value during the observation period. The groups were defined as hypocapnia (< 4.5 kPa), normocapnia (4.5 – 6.0 kPa) and hypercapnia (> 6.0 kPa) in keeping with a previous investigation. 16 The outcome of the hypercapnia and hypocapnia group were each compared with the normocapnia group. Then we compared the outcome of the hypercapnia and hypocapnia group with the outcome of a compound group of the remaining patients. 2. Secondary analyses 2.1 Carbon dioxide amplitude The amplitude in PaCO 2 (∆PaCO 2 ) was calculated as a continuous variable, investigating an association of maximum amplitude in PaCO 2 during the observation period and neurological outcome. 2.2 Carbon dioxide over time We obtained an approximation of the time weighted mean carbon dioxide exposure as an area under curve (AUC) by integrating PaCO 2 over time. The AUC including eight PaCO 2 values was analyzed, investigating an association with neurological outcome over the whole observation period, as well as the AUC of the first four PaCO 2 values, in order to study the influence of early dyscarbia. 2.3 Maximum PaCO 2 and lowest pH analysis The association between maximum PaCO 2 and lowest pH as continuous variables and neurological outcome was evaluated in univariable analyses. Thereafter both variables were introduced into a combined logistic regression model.