## 1 Introduction
### Material and Framework  
When the patient arrives at the referring hospital, the physician on duty meets the patient in the emergency room. Here, the physician considers the patient condition supported by the nurses. If the patient has symptoms of stroke, he/she has to be considered for thrombol treatment. If the physician wants to discuss the patient with a specialist, or if the physician wants to give thrombol treatment, the physician calls up the specialist at a specialist hospital by telephone. In September 2010, the VC service was ready to be used between the two hospitals in Norway included in our study, so that an image of the patient could supplement the spoken description communicated by telephone. In this way, the physicians and nurses at the smaller referring hospital could communicate with the specialist in the specialist hospital, seeing each other and the patient. When the physician calls up the specialist by telephone, he/she initiates the VC meeting, instead of only telephone consultation. While the patient has the CT taken, the specialist and the emergency team (nurses and/or other physicians) connect via VC. After the patient has been CT scanned, he/she returns to the emergency room, where the local team and the specialist through VC are waiting to start the discussion. In September 2010 the service was used for the first time, and it is still running. Each hospital is equipped with the same type of equipment, which reduces possible sources of error. Only minor local adjustments were made due to room configuration. The VC equipment consists of a Tandberg Quick set C60 and a Sony full HD (1080p) television, mounted on a mobile rack (Figure 1). Figure 1: The VC equipment in the emergency room. The Tandberg Quick set C60 has the capability to connect different medical equipment, such as electrocardiography (ECG) apparatus and ultrasound equipment together with two full HD (1080p) cameras. The system may also be used for multipart conferences between more than two locations. It is connected through the Norwegian Health Net [11] (Figure 2), which is a dedicated, secure network for health information. The VC is located in the emergency room at the referring hospital. In the specialist hospital, the VC equipment is located in a dedicated room, used only for this purpose (Figure 3). When the referring hospital calls up the specialist hospital by telephone and initiates a VC meeting, the specialist immediately moves to this room. We consider the empirical field as a network of interacting activity systems, in which the practitioners in the referring hospital and the specialist hospital collaborate, giving the best treatment for stroke patients. Thus, we have a CHAT theoretical framework [12] to understand the activity across work settings. We will argue that objects are culturally and historically developed over time and that activities must be analyzed in relation to practical activities in a wide cultural, social and physical context [13]. Collaborating by using VC requires a patient as an object to discuss. The actions of the  
Figure 3: The VC equipment in the dedicated room. Figure 2: The VC service. subject, the practitioners, are directed toward an object, mediated by both artefacts (tools) and the humans sharing the same object, referred to as the community [12]. VC is the tool providing visual access between the local team and the specialist hospital to share knowledge to improve general stroke treatment and support of thrombol treatment. The subject is related to the community by rules, and the relationship between the community and the object is mediated through the division of labor. The activity is oriented toward an outcome, which is the goal and the motivation for the activity [14]. The two hospitals, the referring and the specialist hospital, form two activity systems that interact with regard to the shared object, _i.e._, the stroke patient. Analyzing collaborative practice has to take place in the zone between the activity systems.