Contrasting characters of quick methods to measure respiratory rate in a clinical setting

Many medical professionals unofficially use quick methods for saving time. However, the evidence of such assessments is limited. The main aim of this article is verifying the agreement of these methods.

Overall, 106 out-patients were simultaneously evaluated with respect to the respiratory time measurement (RTM; 60 divided by the single respiratory time), 15 seconds period quadruple respiratory rate (15secRR; 15 seconds respiratory rate multiplied by 4), and 1-min respiratory rate (1minRR; gold standard respiratory rate).

We assessed the correlation, Bland-Altman plot, kappa value, and normalized root mean square error of the quick methods for the respiratory rate, with 1minRR as the gold standard.

The mean ± SD of 1minRR, RTM, and 15secRR are 20.4 ± 5.6, 19.1 ± 5.7, and 21.4 ± 6.5 breathes per minute, respectively. The correlation between RTM and 1minRR was 0.85 (95% confidence interval [95% CI]: 0.79-0.90), while that between 15secRR and 1minRR was 0.81 (95% CI: 0.74-0.87). The kappa coefficients between RTM and 1minRR, between 15secRR and 1minRR, and between RTM and 15secRR were 0.57 (95% CI: 0.41-0.72), 0.59 (95% CI: 0.43-0.74), and 0.37 (95% CI: 0.20-0.53), respectively. The normalized root mean square error between RTM and 1minRR was 16.9% and that between 15secRR and 1minRR was 15.0%. The Bland Altman plot demonstrated that RTM and 15secRR showed contrasting characteristics.

Compared to the gold standard, RTM tends to underestimate, while 15secRR tends to overestimate the respiratory rate. Therefore, health care professionals should be aware of this methodological tendency to assess vital signs properly.