Clinical validation study of a wireless and wearable sensor for continuous vital signs monitoring in a clinical setting with vital sign ranges limited to the parameters recorded in a post anesthesia care unit

Pulse oximeters are one of the most frequently used non-invasive vital signs
monitors today. Their clinical importance has increased during the recent
Covid-19 pandemic, after it was documented that many patients with Covid-19 may
suffer from *silent hypoxemia* (severe oxygen desaturation without obvious
respiratory distress) [1]. Such episodes of undetected severe hypoxemia are
likely to contribute to hypoxic organ injury and mortality from Covid-19 [2].

Most pulse oximeters require the photoplethysmography (PPG) sensor to be placed
on a well perfused part of the body, such as a finger, toe or the earlobe to
maximize the recorded pulse amplitude and improve accuracy. Unfortunately,
current *wired* pulse oximeters are extremely sensitive to artefacts resulting
from patient movement causing traction on the sensor via the wire (and
sometimes complete sensor dislodgment). This problem is most obvious with
finger and wired ear sensors, which makes them less useful for continuous
monitoring in mobile patients during activities of daily life [3].

In 2010, a Dutch start-up company (FastFocus BV, Harmelen, NL) introduced an
early prototype for a wireless ear patient monitor. That prototype was not yet
clinically usable at the time, mainly because of limited battery life. In the
last years, the company has developed a new iteration of this wearable wireless
patient monitor (CE marked as medical device in March 2021) that pairs high
user comfort with accurate performance of physical activity measurements.
Recently, monitoring of vital signs has been added to the next generation of
the device that pairs user comfort with measurements of blood oxygen saturation
(SpO2), pulse rate and respiratory rate. The battery life of the rechargeable
sensor has now been extended to 14h, allowing only two device change per day to
recharge the unit.

In our ongoing remote patient monitoring research program, we currently
investigate various strategies for remote monitoring of vital signs, both on
regular hospital wards as well as in the patient*s own home setting. A reusable
wearable wireless pulse oximeter that has good resistance to motion artefact
and does not interfere with daily activities is highly desirable. Yet, there
are currently no validated wearable pulse oximetry sensors that are able to
continuously monitor vital signs from locations other than a finger. An
accurate comfortable vital signs ear sensor that has high patient acceptability
might fill the current void.

In the current protocol, we propose to evaluate the clinical performance of the
pulse oximeter function of the FastFocus wearable vital signs monitoring system
in surgical patients in the recovery room.

Primary Objective: To study whether the pulse oximeter functionality of the
wearable ear sensor is able to reliably measure oxygen saturation, pulse rate,
and respiratory rate in a clinical (postoperative) setting.

Secondary Objective(s): To evaluate the usability of the ear sensor from a
patient perspective, including evaluation of any discomfort that might result
from wearing the earsensor.

This is a methods comparison study in hospitalized surgical patients on the
post-anaesthesia care unit. Blood oxygen saturation, pulse rate, and
respiratory rate will be continuously recorded by the sensor in the period
after surgery. The accuracy of the sensor is evaluated by comparison of the
devices to a clinically validated reference standard and patient comfort and
experience will be evaluated using a questionnaire.

With this study we aim to determine performance and the amount of agreement
between the vital signs (SpO2, pulse rate and respiratory rate) of the
EarSensor and the standard (wired) hospital monitor in a high-care setting. It
is not a study to clinically validate the detection of hypoxia in patients,
since patients will receive standard clinical care while admitted at the
post-anesthesia care unit where clinicians could intervene directly based on
the information from the bedside monitor.

The sensor under investigation is ultra-lightweight wireless sensor. The
hardware is identical to FastFocus* Wireless Patient Monitoring System which is
CE marked as class II-a medical device. The slight pressure that is applied on
the skin may cause discomfort. However, a first feasibility study showed that
this risk is minimal. Since physical discomfort of these sensors is unlikely,
patient burden is minimal