Respiratory rates observed over 15 and 30 s compared with rates measured over 60 s: practice-based evidence from an observational study of acutely ill adult medical patients during hospital admission.

ABSTRACT

BACKGROUND: Respiratory rate is often measured over a period shorter than 1 min and then multiplied to produce a rate per minute. There are few reports of the performance of such estimates compared with rates measured over a full minute. AIM: Compare performance of respiratory rates calculated from 15 and 30 s of observations with measurements over 1 min. DESIGN: A prospective single center observational study. METHODS: The respiratory rates calculated from observations for 15 and 30 s were compared with simultaneous respiratory rates measured for a full minute on acutely ill medical patients during their admission to a resource poor hospital in sub-Saharan Africa using a novel respiratory rate tap counting software app. RESULTS: There were 770 respiratory rates recorded on 321 patients while they were in the hospital. The bias (limits of agreement) between the rate derived from 15 s of observations and the full minute was -1.22 breaths per minute (bpm) (-7.16 to 4.72 bpm), and between the rate derived from 30 s and the full minute was -0.46 bpm (-3.89 to 2.97 bpm). Rates observed over 1 min that scored 3 National Early Warning Score points were not identified by half the rates derived from 15 s and a quarter of the rates derived from 30 s. CONCLUSION: Practice-based evidence shows that abnormal respiratory rates are more reliably detected with measurements made over a full minute, and respiratory rate measurement 'short-cuts' often fail to identify sick patients.