Marga Hoogendoorn

66 subtracted this from the 80% of productive nursing time, which sicker patients differ from those in less sick patients. However, according to Armstrong et al. NAS scores in intermediate care patients did not differ from those in ICU patients 25 . Finally, our study does not correct for the nurses years of experience on the ICU or level of education. In the analysis we included student and registered ICU nurses but further research in larger groups should investigate whether different groups need different weighting of NAS points. Based on our results we believe there is room for improvement in the measurement of nursing workload. The NAS could be improved by adjusting the NAS points given to the different items. The developers of the NAS did not report the Pearson’s R or R 2 , but stated that the NAS is reflecting 81% of total nursing time. About 11% of the nurses’ time is spent on personal activities. The remaining 8% comes from nursing activities derived from medical interventions, related exclusively to the severity of illness of the patient not measured by the NAS 7 . The TISS takes these medical interventions into account, such as induced hypothermia, cardiac assist device, pacemaker monitoring or ECG monitoring. For this reason, we suggest additional research towards the merging of the TISS-28 and the NAS. The models could be partly combined which could possibly improve the estimation of nursing workload. Our results on observed time per patient and per nursing activity could be taken into consideration when assigning weighting to the activities in this new model. Moreover, we think that expressing nursing activities in minutes or hours would be more informative compared with points, since it is more straight forward for ICU managers to work with. CONCLUS I ON TheNASwas developedmore than 15 years ago and significantly overestimates the nursing time needed for ICU patients in the current daily ICU practice. Therefore, we recommend a revision of the time weighting assigned to each nursing activity to gain better insight into the true nursing workload and to enable a more effective nursing capacity planning. D I SCLOSURES The data that support the findings of this study are available from the National Intensive Care Evaluation (NICE) but restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly available. Data are however available from the authors upon reasonable request and with permission of the NICE registry. The department of medical informatics (with C.C. Margadant, S. Brinkman, and N.F. de Keizer as employees) receives funding for data processing of the