The empirical application of flow situations used in this study resulted in 23 participants being in a flow situation on different occasions, and 11.5% of the total number of observations was flow situations. Flow at work can be linked to work-related employee enjoyment, since individuals who enjoy their work are more often reporting flow at work [12, 16, 18, 26]. However, studies on the hospital work environment have instead been highlighting problems in work design and management, with adherent work-related dissatisfaction, emotional exhaustion or strain [1, 4]. From our point of view, it is likely that these problems limit the possibility for work-related enjoyment among nursing staff in general, indicating a possibility for improvement of the work environment with adherent facilitation of flow situations. We found no significant relationship between flow situations and social context in our study, a result that is supported by Allison's and Duncan's  conclusion that flow can be experienced alone, as well as in interaction with others.
Csikszentmihalyi  talked about autotelic personality individuals being more likely to experience flow, and Eisenberger et al.  showed that flow, among achievement-oriented employees only, was associated with a positive mood as well as task interest and performance. These personality traits may explain the individual differences in observed flow situations within our material. We could not, however, find any relationship between share of observed flow situations and age group, profession or SOC level. A variation in flow-related personality traits is thus probably not related to any of the individual variables used in our study. The lack of a relationship between share of flow situations and individual characteristics can also be a result of the small material on individual level in the study.
Flow situations has been more often observed at work than during leisure [18, 26]. Allison and Duncan  found that work, as well as non-work situations, was a resource for flow among professional female workers and that flow among blue collar workers was linked to non-work situations to a greater extent . There was no direct relationship between profession and individual share of flow situations in our study. However, the relationship between taking a break and flow situations, when focusing on the assistant nurses only, is considered supportive of the idea of professionally related differences in flow opportunities among female workers. A previous study described the character of taking a break, as well as the relationship between the assistant nurses, in a way that is considered similar to social (non-work) situations in general .
Another indirect link between profession and flow opportunities can be related to the activity-associated results in this study. The results showed that being involved in medical care was positively related to flow situations, and the registered nurses reported being occupied in medical care more often than the assistant nurses. The profession-related activity difference indicates that registered nurses generally have better opportunities for flow experiences, since registered nurses in Swedish health care organisations are normally more occupied in medical care . Blue-collar workers generally have less opportunity for flow when they are at work according to Allison and Duncan . Profession-related differences can be a result of individual characteristics, if for instance individuals with an autotelic personality are more prone to becoming registered nurses or professionals in general. It is thus more likely that the profession-related differences are results of work-related situational factors, since 74% of the variance in flow has been linked to situational characteristics when compared to dispositional features .
We found a relationship between cognitive resources and flow situations which can be considered a validation of the cognitive and partly motivational components of the flow construct. However, we found no significant association between affective resources and flow situations. This pattern can be recognised from the work of LeFevre , who also found that people in general experience more positive affect the more time they spent in a state of flow. This means that if the opportunities for flow were increasing and the participants in our study were to experience flow in the flow situations, they would also experience positive affects more frequently, with adherent possibilities for health. Different studies have reported a relationship between positive mood and flow [15, 19] and flow seems to be important for the psychological well-being in general . Experiencing positive affects have also been considered health-promoting in a general sense .
The empirical findings in this study indicate that research focusing on flow can be an important contribution to the research field of work and health in nursing contexts. Focusing on the positive side of nursing practice, like for instance flow, means knowledge development of the salutogenic components of nursing. These components give opportunity for a nursing practice characterised by positive aspects instead of the traditional problem-oriented and pathogenic focus. Nursing practice with a positive frame of reference is a way of promoting the health of health care workers and improves the opportunity for high quality nursing practice . This will hopefully make nursing practice more attractive and reduce the amount of registered nurses who want to leave their nursing jobs. Further research is needed for an empirical assessment and exploration of relationships between health, subjective experiences of flow in general and affective resources in particular and flow situations in nursing, as they have been operationalized in our study.
Using the ESM in a hospital setting is a complicated and challenging endeavour. The design of the study resulted in a mix of quantitative and qualitative planning and preparation phases. The mix of qualitative and quantitative phases throughout the research process fits Johnson and Onwuegbuzie's  description of a mixed model approach in mixed method research. The initial observations at the ward facilitated the validity because of the adherent possibility to make sure that the participants' everyday practice was systematically covered in the study. The results from the observations were also useful and increased the validity in relationship to the labelling and categorising of the activity responses. The qualitative steps, with adherent researcher-subjective interpretation, could, however, be considered a limitation of the study's reliability. The participants' verification of the observation findings has hopefully, on the other hand, limited any possible negative impact on the reliability. ESM with an ESF is considered a valid and reliable method for measuring various dimensions of experience  and useful for studying everyday life in general . However, the research process needs a number of different steps in order to yield a manageable data material with the possibility for valid and reliable results in the end. We have tried to describe the process thoroughly, to help the readers understand what has been done and judge the credibility of the findings.
Most of the respondents have previously reported having a normal everyday life throughout an ESM study period , and in our study, participation was found to be manageable and somewhat amusing during everyday work. The within context character of the study reduces the risk for recall bias and the ecological validity is strengthened by a habituation process, related to respondents completing the Experience Sampling Form (ESF) repeatedly . One of the problems with repeated measures is that it counteracts the assumption of observations independence . In this study, the problem was solved by differentiating between individual level data and response level data, and analysing them separately. Using individual level data is recommended , but the small number of participants in this study (n = 31) limited the possibility for advanced analysis of the individual level data.
Measurement of flow situations through people's estimates of challenges and skills can be, and have been, done in numerous and varying ways , resulting in inter-study comparison limitations. In this study, we have chosen to use raw scores and defined the flow situation as estimates above five on the ten-graded Likert scale (0-9) and a perfect match between the respondents' answers on challenge and skills. This definition of the flow situation is recommended, since it acknowledges individual differences in the data and is considered to be in line with the respondents' opinion on what constitutes a match between challenge and skill estimation . From our point of view, flow situations should be a relatively rare phenomenon, since flow is described as a subjective experience of enjoyment, complete absorption and a moment where capabilities are being stretched to facilitate learning, and increase self esteem and personal complexity [3, 18].
In most studies of flow, items for constructing affect and arousal indexes are included . In this study, the items included were categorised as cognitive and affective resources, respectively. Customary use of indexes of affect and arousal in studies of flow, despite rather low values of internal consistency, has been criticised . The indexes used in this study were, however, based on a PCA with good quality according to the psychometric properties, and the Cronbach's alpha values were as high as 0.86 and 0.82, respectively.