With better quality sound, reproducibility potential for computer analysis, file-sharing and verification, this new approach offers many benefits, as two Canadian researchers tell the ERS annual Congress in Stockholm.
The traditional stethoscope, fast approaching its second centenary, could soon have to give way to new digital technologies, which are undergoing spectacular development. Even the latest electronic stethoscopes cannot rival MP3 players, used today mainly for leisure purposes. So explained Neil Skjodt, of the Department of Medicine at the University of Alberta (Edmonton, Canada), in his presentation to the annual Congress of the European Respiratory Society (ERS) in Stockholm.
Working with an audiologist colleague, Bill Hodgetts, Skjodt based his analysis on the conclusions of several recent studies, which had demonstrated that health care staff generally had mediocre auditory faculties, especially when using stethoscopes. In particular, a Danish study had shown two years earlier that medical staff at all levels had difficulty distinguishing most heart and lung sounds, and that their performance barely improved when they used an electronic stethoscope.
Two more recent studies had found that medical students sometimes had to listen to certain clinical sounds up to five hundred times before they could recognise them accurately. Yet there are few electronic instruments that make it possible easily to record, reproduce or store the sounds heard during a medical consultation. Not to mention the possibility of transmitting such sounds to databanks so that other doctors may refer to them later.
Better than a stethoscope
At the same time, the increasingly popular portable MP3 recorder/players, used primarily for music, are selling in vast numbers and becoming a major presence on the market. This gave Skjodt and Hodgetts the idea of studying whether the classical stethoscope could be replaced by a cheap off-the-shelf MP3 recorder/player.
By pressing its microphone directly to the chest, they were able to record a whole range of respiratory sounds with different patterns. Different baseline breath sounds with or without added wheezing were studied. "The quality, clarity and purity of the loud sounds were better than I have ever heard with a stethoscope", Skjodt told the Stockholm audience. The MP3 files were later transferred to a computer and converted into frequency curves. Computer analysis of the stored sounds showed that each had a distinct signature. The computer - like the human ear - did, however, sometimes have difficulty in processing complex or quiet breathing sounds.
Skjodt then tested the trainee respiratory specialists to identify the MP3 recordings of breath sounds- with mixed but promising results. Wheezing noises were recognized much better than in similar historic studies, but differences in baseline breath sounds and in recognizing combinations were still not better than chance. Skjodt and Hodgetts plan to see if brief training and ability to use reference recordings could improve auditory recognition.
Unequalled multi-tasking potential
"The improved quality is only one of the benefits", Skjodt emphasised, "and there would be many other advantages to using an MP3 device instead of a stethoscope." Indeed, the recorded breathing sounds can be included in the patient's file for future reference. They can also be sent to a specialist, or processed with more sophisticated software for particularly detailed analysis. In addition, the MP3 recorder can, of course, be used to replace an ordinary dictaphone for medical reports, or to register conferences, as well as patient interviews. And, naturally, to listen to music out of hours…
The Canadian researchers will now continue their study, examining other clinical sounds and assessing the impact of more highly developed audio techniques on sound recognition by the human ear. Doctors could find this particularly useful at patients' bedsides.
European Respiratory Society