Stethoscope works differently than thought

The stethoscope – seemingly one of the simplest diagnostic devices – works differently than thought. – There is a need to correct information that has long been repeated in textbooks for doctors, says Dr. Ing. Lukasz Nowak, who is working on a new generation stethoscope.

Acoustician Dr. Eng. Lukasz Nowak of the Institute of Fundamental Problemsoin Techniki PAN is working with a team on a modern digital stethoscope. The device is supposed to process body sounds so that the doctor can more clearly hear any disturbing signals arising in the patient’s body. While working on the electronic device, the teamoł dr. Nowak studied the properties of traditional acoustic stethoscopesow, used by doctors on a daily basis. And the results turned out to be surprising.

Polak’s workow have shown that an ordinary stethoscope works a little differently than the books explain, with ktor which future doctors learn. – Movery much to the point, all medical textbooks should be improved in this regard, because they mislead doctors, the acoustician believes. Research on the subject appeared in the journal "The Journal of the Acoustical Society of America".

Two endowki

Some of the stethoscopesow is equipped with two roendowki. On one side of the head – whichoThe one that is applied to the patient’s body is a diaphragm, and the other is a funnel. Doctors are taught, says Dr. Nowak, that each of these endowek of the stethoscope filters the sound differently. The diaphragm of a stethoscope would attenuate lower-frequency sounds (lower sounds), helping to supposedly m.in. lung study. However, the finalohe funnel would mute the higher components of sound (those with higher frequencies) and thus do a better job of e.g. In a heart auscultation study.

But it turns out that this is not quite true.

– We question whether the subojne heads in stethoscopes are legitimate,” comments the acoustician. He adds: from our research, we found that neither the finalowka with a funnel, nor with a membrane have filtering properties. And the funnel simply transmits slightly quieter signals, because it has a smaller surface area.

Dr. Nowak talks about previous studies, with which theoThe results showed that the endoThe stethoscope’s rotically filter the sound. – This research was carried out under conditions not quite similar to an ordinary auscultatory examination, says a scientist from the IPPT PAN. This is because the stethoscope was suspended over a loudspeaker and checked how sounds flowed through it. – This idea did not quite make sense. Well, after all, during the examination the doctor applies the head of the stethoscope to the patient’s body, and does not listen to the sound of theoIn the air – mowi Nowak. He explains that the head pressed against the patient’s body forms a new mechanical system with the patient, whichowhich sound propagates differently. – This is an effect thatorego cannot be neglected,” he comments.

Debunking the myths

Therefore, the Poles have proposed a method of performing acoustic examinations, in which theowhich indeed the stethoscope is applied to the patient’s body, and the examination poroThe stethoscope is used in conjunction with a simultaneous ECG. – With our methodology, it is possible to objectively assess and poroThe results of the study showed that the end of theos stethoscopeoin medical,” describes Dr. Nowak. This method has allowed Poles to dispel the myth about roThe differences between the endowkami.

Another of the mythow about stethoscopes, whichory were debunked by Poles, is a myth associated with the operation of the so-called “lentils”. two-ton stethoscope membrane. This diaphragm, if pressed against the body, clasps on the ring underneath the. – Such a diaphragm is boasted by almost all manufacturers of stethoscopesoin, not citing objective sourcesodła – says the scientist. He explains that when the head is pressed more firmly against the patient’s body, there is a filter effect – higher sounds can be heard better, which is supposed to help the doctor in diagnosis.

From the research of Polakohowever, the result was that it is not at all the characteristic structure of the diaphragm that causes sounds to be filtered during the examination. The sound simply changes, because when the head is pressed against the body, the patient’s tissues deform and the higher-frequency components of sound are better transmitted. Thus, the filter effect occurs even when a microphone not equipped with any diaphragm is pressed firmly against the body.

No more paper tube

The scientist says that during an examination with a stethoscope, the doctor is able to e.g. recognize heart murmurs or crackles in the lungs. These disturbing noises may be related to m.in. with a turbulent flow of fluid or air in the body, which in turn could indicate, for example. of structural defects in a particular tissue. However, according to the researcher, an accurate description of the acoustic phenomena accompanying auscultation of the patient is still far from completeow.

– The stethoscope – although it would seem to be a simple instrument – is, in my opinion, the least recognized diagnostic device to date, smiles Dr. Nowak.

– In 1816, French physician Rene Laennec was said to have auscultated a patient. However, since he was shy, he saved himself by applying a rolled up roll of paper to her body. It turned out that by doing so, it was possible to hear the heartbeat better. In this wayob invented the stethoscope,” says the scientist. He adds, however, that the possibilities offered by auscultatory testing are much greater. And progress in this area has quickly stalled. – It’s high time to move away from solutions that mimic a rolled up piece of paper. There are huge opportunities for the development of auscultatory studies. And we know how to use them – mowi researcher.

Acoustician from IPPT PAN wants in the analysis of the soundoin coming from the body use new technologies and develop the next generation of small portable stethoscopeoin electronic. Digital filters, ktore developed by the researchers, could extract from the sound during auscultation examination features indicative of pathologies and improve the accuracy of the diagnosis made by the doctor.

The research is being carried out under the LIDER program of the National Center for Research and Development.