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Error in respiratory rate measurement by direct observation impacts on clinical early warning score algorithms
  1. Andrew W Fogarty1,
  2. Tim Card1,
  3. Dominick Shaw1,
  4. Joe West1,
  5. Mark Simmonds2,
  6. Colin J Crooks1
  1. 1 NIHR Biomedical Research Centre, School of Medicine, University of Nottingham, Nottingham, UK
  2. 2 Nottingham Universities Hospitals NHS Trust, Nottingham, UK
  1. Correspondence to Dr Andrew W Fogarty, Epidemiology, University of Nottingham, Nottingham, NG7 2RD, UK; andrew.fogarty{at}

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Respiratory rate(RR) is the only vital sign that is currently measured by direct observation in many high-income countries in many healthcare settings. However, when relying on direct observation by humans, values may be susceptible to measurement error. In particular, a continuous variable like RR may be inadvertently semicategorised due to rounding and/or multiplying up counts from shorter periods to give estimated counts for a full minute.

This could have an important impact on early warning scores, as these scores rely on the aggregation of accurately measured physiological parameters to trigger specific warning thresholds. Systemic errors in the measurement of RR component could therefore negatively impact patient care if it meant a deteriorating patient did not meet the defined threshold. Seventy-six per cent of UK hospital trusts receiving acute medical admissions use the National Early Warning Score—2 (NEWS-2).1 2 Introduced in 2017, it uses six simple physiological parameters which are respiration rate, oxygen saturation, systolic BP, pulse rate, level of consciousness and temperature. These are aggregated by a simple scoring system that uses predefined thresholds to give a composite …

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  • Handling editor Edward Carlton

  • Correction notice Since this letter was first published online, the author surname Simmons has been updated to Simmonds.

  • Contributors The concept was devised by AF and DS, and used data were collected by JW, CC, TC and MS. CC and AF did the statistical analysis. All authors contributed to the text of the final manuscript.

  • Funding This work was funded by University of Nottingham and NUH NHS Trust.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.