Continuous monitoring of vital signs using wearable devices has long been recognised as having the potential to improve detection of deterioration more quickly than intermittent vital-sign measurement. However, current systems have limitations such as accuracy, reliability and wearability. The Virtual High-Dependency Unit (Virtual HDU) study is a multi-phased project, run by the NIHR Oxford BRC Technology and Digital Health team, to refine and develop an ambulatory monitoring system that is wearable, reliable and user-friendly.
Wearability and accuracy testing
In the initial stages of the study, several devices were selected for wearability and locational testing. The results of this work allowed selection of the most comfortable devices with reliable Bluetooth and Wi-Fi connectivity to be selected for further evaluation.
Devices which were deemed sufficiently comfortable were then tested for accuracy under simulated hospital conditions. Healthy volunteers wearing several test devices followed a pattern of typical patient movements (such as drinking from a cup and turning pages in a book). We then artificially reduced the levels of oxygen in participants’ blood, to test how well the devices detected hypoxia (low levels of blood oxygen). We compared the continuous readings of oxygen saturations from the devices with both ‘gold standard’ (measured levels of oxygen in the blood) and ‘clinical standard’ (wired hospital monitors) tests.
This development work allowed us to select the most comfortable, reliable and accurate devices to be included in the Virtual HDU system.
To inform development of a system which was usable in a ward setting, we conducted qualitative interviews with staff and patients about their experiences of current monitoring practices. We then held focus groups with ward staff to guide development of the system interface.
The final ambulatory monitoring system comprises:
- a wrist-worn pulse oximeter with finger probe, which records oxygen saturations (SpO2) and pulse rate (PR)
- an adhesive chest patch, which records heart rate (HR) and respiratory rate (RR)
- an Android tablet connected to the devices via Bluetooth
- a central station connected to the tablet via Wi-Fi.
The tablet connects to the devices via Bluetooth and is situated in the patient’s room, displaying their vital signs. The tablet then sends patient vital sign information to the central station, situated at the nurses’ station, and displays a card for each monitored patient. More detailed real-time data for each patient are accessed by clicking on each card. It is also possible to check measurement trends over the previous minutes, hours or days. The outcome of this work is a wearable, usable system for ambulatory monitoring of hospitalised patients. This system will overcome the current barriers to traditional wired monitoring.
Use during the 2020 COVID-19 pandemic
Patients diagnosed with COVID-19 have been demonstrated to experience rapidly worsening oxygen saturation levels which require high levels of oxygen delivery. It has been suggested that ambulatory continuous monitoring may assist in detecting deteriorations in patients with COVID-19. At the start of the COVID-19 pandemic, it became clear that the system under development could be usefully deployed to monitor patients in isolation within the Trust. The anticipated benefits of this system included increased staff safety through reduced room entry and PPE donning, and enhanced patient safety through increased surveillance during periods of high acuity.
Development and implementation of this ambulatory monitoring system was accelerated to support the management of patients with COVID-19. The system was delivered to the ward on 20 March 2020 and has been continuously in use on the ward since then. In the first four months of usage 59 patients were monitored for a total of 2,938 hours, with monitoring durations ranging from 1.75 hours to 13 days.
Although implemented during a time of extreme stress and pressure on resources, staff rapidly learnt how to use the system and feedback was positive. Key benefits highlighted by staff were:
- remote monitoring of high-risk patients
- ease of system use
- ability to use trends as part of clinical judgement.
This project has already had an impact on patient care. The research team, in collaboration with ward staff, is continuing their work on further improvements to optimise the system. This will include linking the wearable monitoring system to the electronic patient record (EPR), displaying ECG waveforms, and implementation of an alerting system to assist staff in rapidly identifying deteriorating patients. The system will also be rolled out to other areas in the hospital caring for patients with COVID-19. The systems allowed us to collect detailed physiological data on patients admitted to hospital with COVID-19, which could contribute to further understanding of the impact of the disease and inform clinical management in future.
Refinement of the system, including designing and testing alerts, is ongoing, and guided by staff and patient feedback. The next stage of this project will be to feasibility test the complete system on a surgical ward, to assess the impact on patient and staff-related outcomes.