Marga Hoogendoorn

56 measurement of nursing activities 4 . The study by Stafseth et al. suggests that the reliability and validity of the NAS are good. However, this study strongly suggests more research in other countries and larger groups of patients 10 . Furthermore, research has demonstrated that the work- sampling approach, as used for the development of the NAS, does not lead to an accurate representation of the true nursing workload. This is due to the fact that the weighting of nursing activities is based on the probability that a particular nursing activity occurred 11 . The total amount of time in a shift is divided over the nursing activities that were carried out. When nursing activities frequently occur or take a lot of time, they would also occur more frequently in the work-sampling approach. However, this approach will not lead to precise measurements, but will only approximate the time of the different activities. Thus, in contrast to time- and-motion techniques in which every minute of a nursing shift is measured, the work- sampling approach does not measure the real amount of time spent on nursing activities, which could lead to less accurate results 12 . Therefore, the time-and-motion technique is considered the best technique for time measurement 13 . The aim of this study is to validate the NAS in the Dutch ICU setting using the time- and-motion technique, and to identify which nursing activities are underestimated or overestimated in the NAS. METHODS Setting We conducted an observational study. All 82 Dutch ICUs participate in the National Intensive Care Evaluation (NICE) quality registry. Fifteen of these ICUs are participating in the newly implemented voluntary nursing capacitymodule 14 , seven of which voluntarily took part in this study. Data on characteristics of the ICUs (such as number of ICU beds) and data on patient characteristics (such as age, BMI, admission type, and mortality) were extracted from the NICE registry. Time-and-motion The study involved time-and-motion measurements for patients admitted to the ICU. We included different types of hospitals (academic, teaching and non-teaching hospitals) and different shifts (day, evening and night). We performed an equal number of measurements in all types of hospitals and shifts. At the start of a shift, one nurse was chosen by the observer. The patient(s) that were under the responsibility of this nurse were followed by