Marga Hoogendoorn

92 the association between nursing satisfaction with the perceived nursing workload we also assessed the association of nursing workload satisfaction with the different subcategories of the perceived nursing workload as measured with the NASA-TLX. METHODS Study design and setting We invited 15 Dutch ICUs already recording workload scores or with an intention to participate in the capacity module of the NICE quality registry 16 that includes a workload registration, to participate in this study on a voluntary basis. The nurses of the participating hospitals were informed about the study in a newsletter. From October 1 st , 2016, and November 30 th , 2017, we prospectively measured the objective nursing workload, the perceived nursing workload, and the satisfaction of the ICU nurses with the workload during their shift. Nurses were approached by the researcher to participate in this study on a voluntary basis. Variables Objective nursing workload For the measurement of the objective nursing workload we used the Nursing Activities Score (appendix 2). The Nursing Activities Score represents a total of 23 nursing activities in direct and indirect care (e.g. hygiene procedures, mobilization and positioning or administration tasks) with a translation into a score, representing the mean nursing time needed for this activity 17,18 . A total Nursing Activities Score of 100 has been defined equally to the time spend by 1 Full Time Equivalent (FTE) nurse per shift. The Nursing Activities Score is validated with time measurements 17,18 . Research has shown that the Nursing Activities Score explains 59 - 81% of the actual nursing time 17,19 . The interrater reliability of the Nursing Activities Score showed variable results (Kappa 0.02 – 0.69) 20,21,22 . The Nursing Activities Score is the most common system for measuring nursing workload all over the world 18,23 . Perceived nursing workload For the perceived nursing workload we used the NASA-Task Load Index (NASA-TLX). The NASA-TLX is a validated questionnaire originally developed to measure the perceived workload in aviation 24 (appendix 4). The NASA TLX has been shown to be reliable for the measurement of the perceived workload in different settings, including health care 25,26 . It is a commonly used system to assess the perceived nursing workload on the ICU 27,28 . The NASA-TLX is a six-item scale representing six aspects of perceived workload: mental