Centile-based early warning scores derived from statistical distributions of vital signs

Institute of Biomedical Engineering, Old Road Campus Research Building (Off Roosevelt Drive), University of Oxford, Oxford OX3 7DQ, UK.
Resuscitation (Impact Factor: 3.96). 03/2011; 82(8):1013-8. DOI: 10.1016/j.resuscitation.2011.03.006
Source: PubMed

ABSTRACT To develop an early warning score (EWS) system based on the statistical properties of the vital signs in at-risk hospitalised patients.
A large dataset comprising 64,622 h of vital-sign data, acquired from 863 acutely ill in-hospital patients using bedside monitors, was used to investigate the statistical properties of the four main vital signs. Normalised histograms and cumulative distribution functions were plotted for each of the four variables. A centile-based alerting system was modelled using the aggregated database.
The means and standard deviations of our population's vital signs are very similar to those published in previous studies. When compared with EWS systems based on a future outcome, the cut-off values in our system are most different for respiratory rate and systolic blood pressure. With four-hourly observations in a 12-h shift, about 1 in 8 at-risk patients would trigger our alerting system during the shift.
A centile-based EWS system will identify patients with abnormal vital signs regardless of their eventual outcome and might therefore be more likely to generate an alert when presented with patients with redeemable morbidity or avoidable mortality. We are about to start a stepped-wedge clinical trial gradually introducing an electronic version of our EWS system on the trauma wards in a teaching hospital.

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Available from: L. Tarassenko, Dec 17, 2013
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    • "For instance, Clifton et al. [25] compared Gaussian mixture model (GMM) and support vector machine (SVM) with HR, RR, SpO2, and SysBP as input. Tarassenko et al. [26] developed a centile-based early warning score system based on statistical properties of the vital signs (HR, RR, SpO2 and SysBP) to identify deteriorating patients. Scores were determined when the statistical value of vital sign fell into certain range of centile. "
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    • "The latter shows that most observations are taken at intervals of several hours, with a mean of 4.1 h between observations (but often rising to as long as eight h between observations). This current standard of care for " predictive monitoring, " involving manual observation, has a number of disadvantages. 1) The EWS assigned to each vital sign, and the thresholds against which the scores are compared, are typically heuristic [7]. 2) EWS systems are used with periodic observation of vital signs, which may be made as infrequently as once every 12 h in some wards. "
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