The effectiveness of continuous respiratory rate monitoring in predicting hypoxic and pyrexic events: a retrospective cohort study.

McCartan, Thomas A; Worrall, Amy P; Ó Conluain, Ruán; Alaya, Fátimah; Mulvey, Christopher; MacHale, Elaine; Brennan, Vincent; Lombard, Lorna; Walsh, Joanne; Murray, Myles; Costello, Richard W; Greene, Garrett

Respiratory rate (RR) is routinely used to monitor patients with infectious, cardiac and respiratory diseases and is a component of early warning scores used to predict patient deterioration. However, it is often measured visually with considerable bias and inaccuracy. OBJECTIVES Firstly, to compare distribution and accuracy of electronically measured RR (EMRR) and visually measured RR (VMRR). Secondly, to determine whether, and how far in advance, continuous electronic RR monitoring can predict oncoming hypoxic and pyrexic episodes in infectious respiratory disease. APPROACH A retrospective cohort study analysing the difference between EMRR and VMRR was conducted using patient data from a large tertiary hospital. Cox proportional hazards models were used to determine whether continuous, EMRR measurements could predict oncoming hypoxic (SpO2 <92%) and pyrexic (temperature >38 °C) episodes. MAIN RESULTS Data were gathered from 34 COVID-19 patients, from which a total of 3445 observations of VMRR (independent of Hawthorne effect), peripheral oxygen saturation and temperature and 729117 observations of EMRR were collected. VMRR had peaks in distribution at 18 and 20 breaths per minute. 70.9% of patients would have had a change of treatment during their admission based on the UK's National Early Warning System if EMRR was used in place of VMRR. An elevated EMRR was predictive of hypoxic (hazard ratio: 1.8 (1.05 to 3.07)) and pyrexic (hazard ratio: 9.7 (3.8 to 25)) episodes over the following 12 hours. SIGNIFICANCE Continuous EMRR values are systematically different VMRR values, and results suggest it is a better indicator of true RR as it has lower kurtosis, has higher variance, a lack of peaks at expected values (18 and 20) and it measures a physiological component of breathing directly (abdominal movement). Results suggest EMRR is a strong marker of oncoming hypoxia and is highly predictive of oncoming pyrexic events in the following 12 hours. In many diseases, this could provide an early window to escalate care prior to deterioration, potentially preventing morbidity and mortality.