Marga Hoogendoorn

110 The nursing staff data in the capacity module of the NICE registry consists of both the number of certified ICU nurses and trainee-ICU nurses actual present per shift and the number of operational beds per shift. The actual nursing staff data are retrospectively collected by the ICU management or ICU secretary. This staff is also trained in the use of the capacity module and the data definitions. Data quality is assessed with a feedback system in the software on missing and extreme or abnormal data, both in the hospital Electronic Health System and within the NICE-registry database. Statistical analysis Depending on the variable distribution we used mean and standard deviation (SD) to describe normally distributed continuous variables and median and interquartile range (IQR) for non-normally distributed variables. Categorical variables were described by numbers and percentages. Differences between the cohorts were tested with a Chi-square test for categorical variables, a non-parametric Wilcoxon for non-normally distributed continuous variables and Student’s t-test in case of normally distributed variables. Differences were considered statistically significant when they had a p-value of < 0.05. All statistical analyses were performed using R version 3.3.3. RESULTS Baseline characteristics We included data of 36,754 shifts (day, evening, night) of 3,994 ICU patients: 218 patients with COVID-19 and 1,367 non-COVID ICU patients in the COVID-19 period; 147 patients with pneumonia and 2,262 non-pneumonia ICU patients in the non-COVID period. Table 1 shows the baseline characteristics of the four patient cohorts. Comparing the COVID-19 patients with the pneumonia patients, the COVID-19 patients showed a significant lower number of patients with chronic respiratory insufficiency (11.9% versus 37.4%, p<0.001), a higher BMI (Median BMI 27.7 versus 25.7, p = 0.001), higher number of patients requiring mechanical ventilation in the first 24 hours on the ICU (83.0% versus 55.8 %, p < 0.001), longer length of stay on the ICU (median LOS 14 days versus 3.9 days, p<0.001), a higher ICU mortality (28.9% versus 19,0%, p=0.048) and in-hospital mortality (39.0% versus 26.5%, p=0.017). The group of non-COVID patients during the COVID period showed a significant higher number of urgent surgery patients (17.5% versus 10.8%, p<0.001) compared to the non-pneumonia patients and also a higher number of patients requiring mechanical ventilation in the first 24 hours on the ICU (57% versus 60.7%, p = 0.03).