Computerized multichannel lung sound analysis. Development of acoustic instruments for diagnosis and management of medical conditions.

T he stethoscope has been so widely used by clinicians in the diagnosis and management of patients' illnesses that it has virtually become a symbol of the medical profession. Indeed, as pointed out by Reiser in Scientific American, the invention of the stethoscope by Laënnec revolutionized medicine, changing it from an art to a science [1]. Another revolution is now going on. Auscultation of the chest is now being computerized. One of the forces driving this computerization is that it offers the promise of providing improved instruments for noninvasive diagnosis, i.e., tools that do not invade the body or involve the harmful effects of radiation. Comprehensive reviews of the stethoscope's use in aus-cultation of the lung and of the development of computerized analysis of lung sounds have been presented [2]–[4]. There are also some more recent publications that report on employing advanced signal processing techniques for the detection of adventitious sounds that have been developed by a few groups in the field of lung sounds research [6], [7]. This discussion will focus on clinically important applications of this type of investigation and, in particular, on the development of multi-channel lung sound analysis and its clinical importance. The invention of the chest X ray had a large impact on the clinical utility of the stethoscope. There was no doubt that chest X rays were more reliable than auscultation with an acoustic stethoscope in the detection of important lung diseases such as tuberculosis and cancer. Physical examination of the chest also suffers from a variety of problems. Observer variability is a particularly troublesome one as has been shown in numerous studies. There are differences between clinicians in their education and in their use of nomenclature for sounds. There are even differences in the importance they place on auscultation in the first place. Consequently, it is difficult to know when an observation is made whether it is accurate or not; thus, in the medical literature, a number of derogatory statements can be found about the stethoscope. In the 1961 edition of Rubin and Rubin's Textbook of Chest Medicine, the following quote can be found: " The stethoscope is largely a decorative instrument insofar as its value in diagnosis of pulmonary diseases is concerned. Nevertheless, it occupies an important role in the art of medicine. Apprehensive patients with functional complaints are often relieved when they feel the chest piece on their pec-toral muscles " …