Comparison of Respiratory Rate Estimation Based on Tracheal Sounds Versus a Capnograph

The objective was to compare the accuracy of estimations of respiratory rate (RR), based on tracheal sounds, with simultaneous estimations from a capnograph, using as a common reference a pneumotachometer. Five subjects without pulmonary diseases were enrolled. Tracheal sounds were acquired using a contact piezoelectric sensor placed on the subject´s throat and analyzed using a combined investigation of the sound envelope and frequency content. The capnograph and pneumotachometer were coupled to a face mask worn by the subjects. There was a strong linear correlation (r² = 0.98) between the acoustic method and the pneumotachometer and also between the capnograph and the pneumotachometer (r² = 0.98). The SEE obtained by the acoustic method was 1.11 and the SEE obtained by the capnograph was 1.23. As a conclusion, the accuracy of the respiratory rate estimated from tracheal sounds on adult subjects was comparable to the accuracy of a commercial capnograph, using as a common reference a pneumotachometer