Early Detection of Inpatient Deterioration Using Wearable Monitors

Student thesis: Doctoral ThesisDoctor of Philosophy


In spite of numerous quality improvement interventions, delayed recognition of inpatient deterioration is a significant cause of morbidity and mortality. Expert consensus suggests that continuous patient monitoring may have an important role in addressing the problem. The use of conventional bedside monitors for monitoring patients on general (Level 0 and Level 1) wards is poorly tolerated by patients and staff alike. Recent advances in technology have led to the development of a wide range of wearable monitors. This thesis examines the feasibility and efficacy of using wearable monitors to monitor the vital signs of patients in a general ward setting. The feasibility of monitoring was evaluated in two studies. The first was a comparative evaluation of five monitors used to monitor patients for 24 hours. The second study evaluated the feasibility of recording the electrocardiogram (ECG) and photoplethysmogram (PPG) of patients following cardiac surgery for their entire stay on the cardiac surgery ward. Data capture rates in both studies were low overall. ECG was more reliably recorded than PPG. System maturity, patient acceptance and intervention design were identified as key determinant of monitoring success. Based on our experiences we identified a need for better evaluation and implementation tools to assist future studies. We developed and validated an acceptance questionnaire. We also proposed a framework which provides a systematic approach to the implementation and evaluation of wearable monitoring systems. In selecting which vital signs to monitor, there is a trade-off between what is desirable and what is comfortable for the wearer. Respiratory rate, although a sensitive marker of deterioration, was difficult to measure comfortably. Therefore, we undertook an systematic evaluation of algorithms to estimate respiratory rate from the ECG and PPG in order to identify algorithms which might be clinically useful. We identified 4 algorithms which were more accurate than electrical impedance pneumography when operating in ideal circumstances. Further work is required to determine whether performance will be maintained in a real-world context. Finally, we examined whether continuous monitoring offered any advantage over intermittent observations according standard ward practice. We concluded that although individual patients might have benefitted from continuous monitoring, at the population level the benefit was minimal and outweighed the cost of the false alerts. The principle reason for lack of benefit was the low prevalence of abnormal vital signs. Future work should continue to address the technical and practical issues surrounding the design and implementation of wearable monitoring systems. In parallel research needs to be undertaken to gain a better understanding of which care processes are failing, what should be monitored and how the data can be used to improve the reliability of existing care.
Date of Award1 Apr 2019
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorJohn Moxham (Supervisor) & Richard Beale (Supervisor)

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