Diagnosis of Respiratory Abnormalities Using Tracheal Sounds Analysis: Instrumentation and Evaluation in Simulated and In Vivo Tests

Several respiratory diseases introduce increases in upper airway obstruction. This work describes the design and application of a system based on Tracheal Sounds Analysis (TSA) able to evaluate this obstruction. A miniature microphone was used, providing analog signals to a virtual instrument developed in LabVIEW (TM) environment. The design of the instrument is described, as well as in vitro and in vivo results obtained with orifice plates and patients with acromegaly, respectively. It was observed that the mean power (Pm) using orifice plates increased in comparison to that observed for free airflow, which is in agreement with the presence of turbulent airflow, associated with increased resistance. The comparative analysis of the Pm in controls and patients during spontaneous ventilation showed increased values in Pm (p < 0.009) and reduced values of the slope of the regression lines in the spectra (p < 0.006) in patients. These results are in agreement of the physiopathology of the studied disease, and provide clear evidence that TSA is able to detect the increased upper airway obstruction associated with acromegaly. Considering that TSA is performed during spontaneous breathing, requiring minimal patient effort, we concluded that the developed system could be a useful tool for the evaluation of changes in the airway obstruction introduced by acromegaly.