Marga Hoogendoorn

75 score of the Nursing Activities Score per nurse per shift. If a nurse took care of more than one patient, we calculated the total sum score of the Nursing Activities Score of all the patients under that nurse’s responsibility during that shift. Perceived nursing workload For the perceived nursing workload we asked the nurses to fill in the NASA-Task Load Index Task Load Index in a web based digital form at the end of each shift. The score of the NASA- Task Load Index is a total sum score of six subscales representing the mental demand, physical demand, temporal demand, the overall performance, frustration level and effort (appendix 4). Every subscale is rated on a scale of 0 to 10 points. For this study we used the total sum score of the six subscales of the NASA-Task Load Index with 60 points as a maximum score; representing a maximum demand on all subscales. Factors influencing perceived workload We identified various factors that may influence the perceived workload, based on literature and availability of data in a Dutch national quality registry for Intensive Care 18,19,20 . Two health scientists with nursing background, two intensivists, and a clinical data scientist summarized the factors into three categories: patient factors, nursing factors, and contextual factors. We used the following patient factors with potential impact on perceived nursing workload: severity of illness expressed as the APACHE-IV Acute Physiology Score 21 , comorbidities (chronic renal insufficiency, diabetes mellitus, respiratory insufficiency, cardiovascular insufficiency), age, body mass index, and type of admission (planned or unplanned). As nursing factors we included information about educational level (student; i.e. certified nurse in specialization for Intensive Care nurse or certified Intensive Care nurse) and years of experience as a certified Intensive Care nurse (less than two years or two or more years of experience). The contextual factors consisted of the number of patients the nurse had to take care for during the shift, type of shift (day, evening, or night shift), and day of admission or discharge versus in-between days. Data collection We used data from the Dutch quality registry National Intensive Care Evaluation 18 . Currently all Dutch Intensive Cares participate in this registry and upload data regarding among others demographic, physiological and diagnostic data, and in-hospital mortality of all admitted Intensive Care patients. One of the optional modules of the National Intensive Care Evaluation is the nursing capacity-module including the number of Fulltime-equivalent nurses and Nursing Activities Score data per patient per shift. The Nursing Activities Score data in the registry consists of all nursing activities within the