PhiSAS: a low-cost medical system for the observation of respiratory dysfunction

Respiratory illness is recognised internationally as one of the commonest medical disorders affecting the world´s populous, and is especially a major problem that affects the third world. The World Health Organisation (WHO) pursues an extensive health program that is aimed at reducing the plight of respiratory disorders by treatment and education. As with the majority of third-world health care programs, the effectiveness is limited by the availability of resources and finance. PhiSAS (Physiological Signal Analysis System) is a novel system developed for the observation of lung sounds. The system consists of a Personal Computer (PC) supported with dedicated software and hardware. Lung sounds can be recorded via chest microphones into the computer system for storage in digital form. This data can then be retrieved for post-processing using an array of software-based Digital Signal Processing (DSP) techniques that can mathematically manipulate lung sounds to extract important features. Data and results can be presented audibly by sound playback, or graphically by using spectrographs. The spectrograph is a representation of lung sound spectral energy with respect to time and frequency. PhiSAS has the ability to present three types of analysis based on conventional and novel mathematical techniques: Fourier, Wavelet and Time-Frequency Analysis. The purpose of the PhiSAS system is to provide objective analysis of lung sounds. The practice of auscultation (the art of listening to body sounds) has been practiced by physicians since the days of Hippocratic medicine. However, many physicians believe that respiratory auscultation performed with a stethoscope offers little scientific value due to the way it is practiced. For example, observations can be subjective depending on the physicians hearing ability and experience. Moreover, descriptions of lung sounds are described using onomatopoeic references that are ambiguous. By exploiting advances in low-cost PC technology and techniques in signal analysis, the physician can express sound observations in a more precise scientific manner.