Non-invasive wireless continuous monitoring of vital signs using wearable sensors: a clinical validation study

Vital signs monitoring in high-care settings, e.g., the Intensive Care Unit
(ICU) and Medium Care (MC) includes continuous measurement of different vital
signs and frequent (almost a 1:1 nurse to patient ratio) visual observations of
the patient*s clinical status by the nurse. In low care settings such as
general hospital wards, the current standard is intermittent measurement of
vital signs only, typically once every nurse shift (every 8 h). In the first
days after hospital discharge, vital signs are no longer monitored at all.
Although the risk of sudden patient deterioration is expected to decrease
towards the day of hospital discharge, the risk that patient deterioration will
not be noticed increases at each successive transition from ICU to home. Recent
technological innovations have resulted in lightweight *wearable* wireless
sensors. The devices allow * at least in theory - continuous monitoring of the
patient*s vital signs on general wards and even at home. With the wearable
*patch* type sensors HealthPatch (VitalConnect, Campbell, CA) and SensiumVitals
(Toumaz group, London, UK) continuous wireless monitoring of respiration, heart
rate and temperature is possible. The bed-based EarlySense system (EarlySense
Inc., Ramat Gan, Israel), is a contact-less sensor for continuous measurement
of both respiration and heart rate. Although the EarlySense system is not a
wearable, it is possible to measure heart rate and respiration rate wireless
and contact-less. If validated, these sensors therefore can provide early
detection of patient deterioration before complications such as apnea, severe
blood loss and sepsis have occurred. They thus have the potential to improve
patient safety on general hospital wards, without compromising patient comfort.
The wearable variants even allow continuation of monitoring during
mobilization.

The objective of this validation study is to determine whether the wearable
sensors: HealthPatch, SensiumVitals and the bed-based contact-less EarlySense
system are able to detect heart rate and respiratory rate in a clinical
setting, with sufficient reliability to be used as a patient safety monitor. As
a secondary objective, we will assess the experience of patients regarding the
aspects of *wearability* of the sensors and we will investigate the experiences
of nurses who have treated patients with sensors during their ward admission.

This current study is a second step in a longer running research project
regarding the creation of a safer care pathway from ICU via ward to home for
high risk patients by empowering doctors and nurses with remote monitoring
equipment to reduce the risk of unmonitored patient deterioration and to
improve early detection and treatment of vital sign deterioration. Initial
validation of these sensors is being conducted at the Surgical MC and the
Operating Room (OR). In the second phase of this project we intend to perform a
methods comparison study, comparing results of the sensors with a validated
patient-worn monitor (Radius-7, Masimo Corporation, CA, USA), since nurse
controls will not be sufficient to validate the performance of the sensors.
During this study, we intend to validate their performance in patients at the
general surgical ward, including validation during periods of early
mobilization. If the sensors succeed this second validation phase, we intend to
validate their performance in a subsequent study in patients after hospital
discharge at home.

This study describes a methods comparison study with an observational
diagnostic design. During this study the agreement between two methods for
monitoring vital signs (respiratory rate and heart rate) will be quantified,
comparing the new sensors HealthPatch, SensiumVitals and the bed-based
EarlySense system to a validated reference standard during ward admission.
Accepted reference standards here are continuous measurement of pulse rate with
Masimo SET® Measure through motion and low perfusion* pulse oximetry for heart
rate measurements and respiratory rate measurements with rainbow Acoustic
Monitoring*.

In this observational diagnostic study the protocol does not specify any
interventions. Hence, all patients will undergo the same monitoring in a
similar systematic manner, and all treatment decisions will be based on nurse
observations, conforming to all current guidelines on postoperative care. The
sensors that we intend to validate are no longer in the prototype stage. They
all have acquired CE and FDA clearance as medical device.

Intended application: the waterproof adhesive patch sensor will be placed on
the patient*s chest. This position allows remote monitoring without the
inconvenience of physical attachment to immobile bedside monitoring systems. In
contrast to the routinely used reference standard, the patch sensors are not
connected with wires to external equipment and patient movement is
unconstrained. In contrast, the reference patient-worn monitor (Radius-7,
Masimo Corporation, CA, USA) need to be attached to the arm of the patient
connected to a fingertip pulse oximeter and an adhesive sensor in the patient*s
neck for respiratory rate monitoring. Continuous monitoring is not part of
normal routine monitoring with only intermittent measurements of vital signs.
However, the reference patient monitor is lightweight and allows untethered
monitoring while patients are in or out of bed without the need for nursing
assistance to disconnect and reconnect cables. As with any adhesive
plaster/tape, it is possible that some patients will experience skin irritation
in response to the adhesive, in which case the sensor will be removed. Since
physical discomfort from the sensors and the reference monitor is unlikely,
patient burden is minimal. The bed-based EarlySense system will not result in
any patient discomfort, because this mechanical sensor is positioned under the
patient* s mattress.