Fever is a common symptom in many health conditions, but current methods to monitor body temperature (BT) are either invasive, costly, or not continuous. The Corsano CardioWatch 287-2, a wristband that tracks multiple vital signs, offers a new way to monitor BT by measuring skin temperature and heat flux on the wrist. It uses a machine learning algorithm to predict BT in real-time. The device has shown good results when compared to other non-invasive temperature measurements, like tympanic (ear) temperature, in stroke patients. However, it hasn't yet been compared to the gold standard of invasive rectal temperature monitoring in a clinical setting. This study aims to test the accuracy of the Corsano CardioWatch 287-2 in measuring body temperature against rectal temperature monitoring in a clinical environment.

Rationale Fever is one of the most common clinical symptoms. So far, clinically established methods to monitor body temperature (BT) are either invasive and expensive (blood, bladder or rectal catheter) and/or non-continuous (tympanic temperature measurements). A continuous and scalable BT monitoring solution is missing. The Corsano CardioWatch 287-2 is a wristband intended to monitor multiple vital signs, including BT. It does so by continuously measuring the wrist's skin temperature and corresponding heat flux, from which it predicts the BT. These BT predictions are performed in real-time by a machine learning algorithm on the wearable itself. The sensor system was shown to have good correlation with tympanic temperature measurements in an acute stroke clinical setting [1]. However, a clinical validation study in which the temperature sensor of the Corsano CardioWatch 287 is compared to invasive rectal temperature monitoring, is lacking.

Research objective This study's research objective is to investigate the validity of BT measurement through skin temperature and skin heat flux measurement by the Corsano CardioWatch 287-2 against invasive rectal temperature monitoring in a clinical setting.

Primary objective The main objective is to validate the clinical accuracy of BT spot measurements by the Corsano CardioWatch 287-2 according to ISO 80601-2-56;2017+A1;2018 [1,2].

Secondary objective The secondary objective is to compare continuous BT measurements by the Corsano CardioWatch 287-2 with measurements from a clinically conventional, continuous rectal temperature sensor. Bias and limits of agreement for CardioWatch 287-2 will also be calculated in comparison to the rectal temperature probe measurements.

As a third goal, simultaneously available thermometer readings of clinical thermometers, such as Radius-T temperature readings, tympanic temperature readings and rectal temperature probe readings, will be compared with each other to assess the difference in respect to each other.

The fourth goal of this study will be to record and evaluate adverse events from the wearable BT sensor (e.g., rash).

Inclusion Criteria:

• ≥ 18 years old;
• Able to provide consent
• Administered at the ICU or recovery room of the Reinier de Graaf hospita

Exclusion Criteria:

• Unable to wear the Corsano CardioWatch 287 or Radius-T sensor due to reasons such as allergic reactions, wounds, amputations etc.;
• Unable to receive rectal temperature monitoring;
• Thermoregulatory problems or diseases;
• Hyperthermia (>40°C);
• Known allergy to plastics / latex;
• Patient not willing to sign informed consent;
• Significant mental or cognitive impairment.

We aim to include 120 individuals (mixed gender), of which 30-50% are displaying fever (>38°C), who are administered to the intensive care unit or the recovery room of the Reinier de Graaf Gasthuis.