Acoustical Respiratory Flow

Flow estimation from respiratory sounds, in particular tracheal sounds, has drawn much attention in recent years. This article briefly discusses previous studies that have been proposed for flow estimation. Recently, a method based on entropy was shown to have a superior performance compared to the other methods. The robustness of this entropy-based model in terms of its sensitivity to the changes of the tracheal sound signal´s amplitude is presented here. Furthermore, with the aid of a new and simple technique to cancel the effect of heart sounds on the tracheal sound, the method was also able to estimate flow at very shallow breathing, which had not been done in previous studies. Flow variation effects the amplitude of tracheal sound. Therefore, the robustness of any flow estimation method to amplitude and the entropy method in particular is of interest