The web-based survey was conducted as a multi-centre quality assurance measure and quantitative data from potential users were collected as an empirical evaluation procedure. The reporting complied with the CONSORT-EHEALTH checklist (V.1.6.1) by Eysenbach [12] for evaluation reports of web-based and mobile health interventions.

Study Use Case

The study-related use case focuses on the aim of collecting PICS-relevant data for research through the app to be designed in this paper. As part of the national MI-I, this means that data is to be described using international standards (in particular HL7 FHIR) and managed via so-called data integration centers in order to make it reusable for research. Integration into hospital-specific electronic health records or the national electronic patient record is not intended currently. The sole purpose is data collection for research.

In the future, after the patient’s discharge, various parameters (see below) will be entered by the patient himself on his mobile device using the PICOS app, either daily or weekly. This data is transmitted to the data integration centre of the project-specific node of the MI-I. In addition, it is conceivable that the use case could be expanded in the future to include the research findings of this study to support healthcare provision.

Recruitment

Potential future app users over 18 years old were recruited to take part in this survey study. Patients, who had been treated in the ICU for at least 72 h or who had been mechanically ventilated for more than 24 h were eligible to participate. As the aim of the survey is a potential impairment of PICS in former intensive care patients, participants were screened as soon as they met the criteria for potential ICU discharge and were then included upon transfer to the general ward. Pregnant women (due to potentially redundant hospital stay due to other reasons) and patients who were unable complete the questionnaire themselves were excluded. Study nurses approached potential participants on the general ward shortly after their transfer from the intensive care unit to enrol them into the survey study, just as it will be when patients use the PICOS app. The future aim is to ensure that patients can begin using the app while still hospitalized on the general ward, allowing project staff to be readily available for any questions or assistance.The questionnaire was written in German. Patients were recruited from four different hospitals in Germany: University Hospital RWTH Aachen, University Hospital Jena, University Hospital Leipzig and St. Franziskus Hospital Münster.

Prototype of the PICOS app

A clickable prototype of the developed PICOS app created using the prototyping tool Adobe XD. The prototype served to make the planned design tangible and give potential users an impression of the planned functionality and design. The prototype included a main page where the users were able to track their registered vital signs like blood glucose level, heart rate, blood pressure and weight as well as their activity through step tracking, with manual entries or via wearables (e.g. smartwatch). A weekly use of the PHQ-4 questionnaire (patient health questionnaire-4) [13] with a 4-item scale asking for depression symptoms and anxiety was also was also incorporated into the app. No real data were captured when using this prototype.

In the PICOS app, the users receive daily reminders about the completeness of their entries. From the main page, users can access an interface to manage their vital signs directly, update them or indicate if they are not relevant. From the main page, users could also access their medication plan, view their therapy plan, create an overview of caregivers and relatives, save documents, or manage their doctor and hospital visits (see Fig. 1).

The main goals of the design were to create a usable interface with simple and intuitive operations. The user interface followed the principles of usability engineering for interactive systems as formulated in ISO 9241 − 110 as an international standard [14]. The following principles were considered: task appropriateness, self-descriptiveness, conformity to expectations, learnability, controllability, fault tolerance, customizability.

Fig. 1

Screenshots of the PICOS clickable prototype, German version

Left: Main page where users can register their vital signs and activity, Middle: Graphical overview of blood sugar and heart rate over one week, Right: Access to store information such as medication plan, contacts of treating physicians/caregivers and relatives and additional documents as well as an appointment reminder

Questionnaires for Evaluation

The questionnaires for evaluating the PICOS app prototype covered the demographic data of the participants, their interaction with technology and their perception of the prototype. Due to the vulnerability of the target group, the survey was kept as short as possible. The survey was evaluated by an expert panel with four researchers following the recommendations of Ikart [15]. All items used had already been validated and applied in other surveys.

For demographics, participants were asked about their age, their education level and gender identity. In addition, participants were asked if they own or use a smartphone and whether they would like support (e.g., from family members or caregivers) when using the PICOS app.

The interaction with technology was operationalised by the German version of the Affinity for Technology Interaction (ATI) scale developed by Franke et al. [16] and based on the need for cognition-theory [17].

The perception of the PICOS app was measured using the scale by Krishnan et al. [18] which addresses the intention to use CHI (consumer health informatics) applications, based on [19,20, 21]. Because representatives of the target group quickly showed signs of exhaustion during the pre-testing, the number of items had to be reduced by the expert panel to: hedonic motivation, perceived ease of use and performance expectancy. These dimensions showed a significant linear relationship with the adoption behaviour of CHI-Applications [18, 22,23,24,25], so we interpret the overall value for all these dimensions as the intention to use the PICOS app.

Hypotheses

The questionnaires used are intended to analyse the characteristics of the target group and the relationship between the following characteristics:

H1

There is a significant relationship between the affinity for technology interaction and.

a.

…the age of the participants.

b.

…the gender identity of the participants.

c.

…the possession and usage of a smartphone.

d.

…the interest in support when using the PICOS app.

H2

There is a significant relationship between the perception of the PICOS app and.

a.

…the age of the participants.

b.

…the gender identity of the participants.

c.

…the possession and usage of a smartphone.

d.

…the interest in support when using the PICOS app.

H3

: There is a significant relationship between the affinity for technology interaction and the perception of the PICOS app.

Procedure

The web-based survey was conducted between 01.09.2022 and 01.09.2023. It was implemented as an online survey via LimeSurvey, but participants completed the questionnaires with the help of a study nurse. The entire survey took no longer than 15 min.

Statistical Analysis

The collected data were analysed with the IBM SPSS Statistics 28 analysis software and analysed descriptively. Normal distribution was tested by the Shapiro-Wilk test [26]. Correlations were tested through Spearman’s ρ for ordinal variables or rejected normal distribution. For evaluation of the Spearman’s ρ effect sizes, the classification according to Cohen [27] was chosen with 0.10–0.29 as a small/weak effect, 0.30–0.49 as a medium/moderate effect, and > = 0.50 as a large/strong effect. Levene’s Test was used to test for homogeneity of variances with a significance level of 0.05.