A Comparison of Methods to Count Breathing Frequency

Counting breaths for a full minute for all patients to determine breathing frequency could result in excessive work load for many medical staff. The aim of this study was to verify the agreement of 2 quick screening methods with counting breaths for a full minute.

We conducted a cross-sectional study to compare the breathing frequency estimates from a 15-s period multiplied by 4 (15-s quadruple) and a value which is 60 divided by the time measured for a single breath (ie, breathing time measurement) against counting breaths for a full minute. Subjects of this study included 58 nurses; 1 nurse acted as the patient, and 57 nurses counted the patient's breathing frequency using each of the 3 methods. Each nurse examiner performed the breathing time measurement, the 15-s quadruple method, and the 1-min breath count, in that order. We performed correlation and Bland-Altman analyses between the 15-s quadruple and 1-min breath count methods, and between the breathing time measurement and 1-min breath count methods. Using paired t tests, we compared the absolute difference between the 15-s quadruple and the 1-min breath count methods to the absolute difference between the breathing time measurement and the 1-min breath count methods.

The coefficient of correlation between the 15-s quadruple and 1-min breath count was 0.83, while the coefficient of correlation between the breathing time measurement and 1-min breath count methods was 0.90. Brand-Altman analysis indicated that the bias of 15-s quadruple method to the 1-min breath count method was -2.1 ± 2.9 SD, and the limit of agreement was ±5.6; the bias of the breathing time measurement method to the 1-min breath count method was 0.5 ± 2.6 SD, and the limit of agreement was ±5.0. There were statistically significant differences between the 15-s quadruple and 1-min breath count methods and between the breathing time measurement and 1-min breath count methods (P < .001).

The breathing time measurement method had better agreement with the 1-min breath count method than did the 15-s quadruple method in this study setting.