A bioacoustic method for timing of the different phases of the breathing cycle and monitoring of breathing frequency

It is well known that the flow of air through the trachea during respiratio n causes vibrations in the tissue near the trachea, which propagate to the surface of the body and can be picked up by a microphone placed on the thro at over the trachea. Since the vibrations are a direct result of the airflo w, accurate timing of inspiration and expiration is possible. This paper pr esents a signal analysis solution for automated monitoring of breathing and calculation of the breathing frequency. The signal analysis approach uses tracheal sound variables in the time and frequency domains, as well as the characteristics of the disturbances that can be used to discriminate trache al sound from noise. One problem associated with the bioacoustic method is its sensitivity for acoustic disturbances, because the microphone tends to pick up all vibrations, independent of their origin. A signal processing me thod was developed that makes the bioacoustic method clinically useful in a broad variety of situations, for example in intensive care and during cert ain heart examinations, where information about both the precise timing and the phases of breathing is crucial. (C) 2000 IPEM. Published by Elsevier S cience Ltd. All rights reserved.