Respiratory rates measured by a standardised clinical approach, ward staff, and a wireless device.

Abstract

Respiratory rate is among the first vital signs to change in deteriorating patients. The aim was to investigate the agreement between respiratory rate measurements by three different methods. This prospective observational study included acutely admitted adult patients in a medical ward. Respiratory rate was measured by three methods: a standardised approach over 60 s while patients lay still and refrained from talking, by ward staff and by a wireless electronic patch (SensiumVitals). The Bland-Altman method was used to compare measurements and three breaths per minute (BPM) was considered a clinically relevant difference. We included 50 patients. The mean difference between the standardised approach and the electronic measurement was 0.3 (95% CI: -1.4 to 2.0) BPM; 95% limits of agreement were -11.5 (95% CI: -14.5 to -8.6) and 12.1 (95% CI: 9.2 to 15.1) BPM. Removal of three outliers with huge differences lead to a mean difference of -0.1 (95% CI: -0.7 to 0.5) BPM and 95% limits of agreement of -4.2 (95% CI: -5.3 to -3.2) BPM and 4.0 (95% CI: 2.9 to 5.0) BPM. The mean difference between staff and electronic measurements was 1.7 (95% CI: -0.5 to 3.9) BPM; 95% limits of agreement were -13.3 (95% CI: -17.2 to -9.5) BPM and 16.8 (95% CI: 13.0 to 20.6) BPM. A concerning lack of agreement was found between a wireless monitoring system and a standardised clinical approach. Ward staff's measurements also seemed to be inaccurate.