Rationale Following ICU discharge, intermittent vital sign monitoring may delay timely recognition of clinical deterioration and lead to unnecessary readmissions. This study proposes the use of the viQtor continuous monitoring device to measure pulse rate (PR), respiratory rate (RR), oxygen saturation (SpO2) and the activity index in post-ICU patients on general wards. The primary aim is to develop a continuous Early Warning Score (c-EWS), determine its optimal cut-off values. The secondairy outcome will be a comparison with the Modified Early Warning Score (MEWS). In addition, patient and nurse satisfaction, as well as technical feasibility, will be assessed.

Objective(s) Primary: To develop and optimize a c-EWS using viQtor data for early detection of clinical deterioration in post-ICU patients.

Secondary: To evaluate the c-EWS's predictive accuracy relative to MEWS, to assess user satisfaction (patients and nurses), and to determine the technical feasibility of the viQtor device.

Study type This is a single-center prospective observational cohort study at general wards in post-discharge ICU patients.

Study population A single-center prospective observational cohort study will include approximately 180 post-ICU patients and 20 nurses at the Erasmus MC.

Methods Over a four-month period (winter/spring 2024-2025), patients transferred from the ICU to a general ward will wear the viQtor device for up to 5 days. Concurrent standard care involves MEWS measurements three times daily. No clinical decisions will be based on viQtor measurements, ensuring no interference with standard care. The c-EWS will be retrospectively derived and assessed using ROC analyses to determine optimal cut-off values. Comparisons with MEWS will be descriptive. Patient feedback will be collected via a brief questionnaire at discharge, and a semi-structured focus group with participating nurses will provide insights into user experiences.

Burden and risks The wearable viQtor device is noninvasive, comfortable, and worn continuously without affecting patient care or activities. Minor skin irritation is the only anticipated risk. Nurses' participation is limited to the focus group.

Recruitment and consent Patients will be screened in the last 48 hours of their ICU stay. Following informed consent, the viQtor device will be applied at the moment of transfer to the general ward. All participants will be fully informed about study procedures, potential risks, and their right to withdraw. Nurses will be invited via email to participate in the focus group and will provide informed consent before participation.

Inclusion Criteria:

• Adults ≥18 years of age
• Written informed consent is obtained from the patient
• Expected hospitalization time after ICU discharge of 2 days or longer

Exclusion Criteria:

• The patient is unable to communicate in Dutch or English
• The patient has an allergy to metal or plastics (as the viQtor device contains these materials)
• The patient has significant deformities, swelling, irritation, degenerative changes, local infection, ulceration, skin lesions, or edema of the upper arms.
• The patient has tattoos on both upper arms where the device's PPG sensor would be placed
• The patient experiences tremors/and or convulsions affecting the upper arm

This study will be conducted at Erasmus MC and will include 180 hospitalized adults (aged 18 years and older) who have received ICU care and are subsequently transferred to a general ward within the Erasmus MC.