Correlation of Constant Flow Rate with Frequency Spectrum of Respiratory Sounds When Measured at the Trachea

Respiration is one of the critical physiological functions of concern when a patient is under examination or treatment. A clinical relationship between respiratory sounds and gross respiratory pathology was established early in the 19th century by auscultation. It is commonly believed that characteristics of respiratory sounds are related to respiratory flow rate. The objective of this study is to determine the correlation or relationship between spectral composition of respiratory sounds as measured at the trachea and flow rates as measured by pueumotachometer. Respiratory sounds at six contant flow rates were measured with an electronic stethoscope placed at the anterior cervical triangle, inferior to the circoid cartilage. Results indicated that the mean frequency of the power spectrum increases linearly with increase in flow but remains about the same when the flow rate is above 0.75 I/s. In addition, the expiratory spectra have higher mean frequencies than inspiratory spectra.