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Developing a germ-free stethoscope

Stethoscopes are used in nearly every patient examination, and they belong to the basic equipment of general practitioners. To prevent the transmission of germs, medical specialists should disinfect the device after each patient contact. An invention by a 16-year-old girl could simplify this hygiene measure immensely.

A self-disinfecting stethoscope – this was the idea of 16-year-old Rieke-Marie Hackbarth.
For her project in the 2015 German youth science competition, “Jugend forscht”, she investigated the subject of stethoscope hygiene1.

Stethoscopes are important for diagnosing diseases

Doctors have used stethoscopes for decades because these instruments help them to diagnose breathing noises related to pleurisy, pneumonia or heart defects reliably and without great effort. During auscultation of the heart and lungs, vibrations of the body are transmitted to the stethoscope membrane and thus to the ear of the physician.

As useful as such medical devices are, they can quickly become a source of infection if they are not frequently disinfected. A study from 20142 shows that the infection potential of a non-disinfected stethoscope is similar to that of a non-disinfected doctor’s hand. The membrane of the stethoscope was more contaminated with normal and multi-resistant pathogens than all areas of the hand, with the exception of the fingertips.

Development of self-disinfecting stethoscope in two years

The student Rieke-Marie Hackbarth was looking for a simple solution to this risk of infection. Within two years, she developed a stethoscope that automatically disinfects itself after each patient check. It is absolutely germ-free again until the next patient contact. A microchip makes this possible: When physicians remove their thumbs or index fingers from the stethoscope following examinations, the integrated chip receives a signal. A few seconds later, it initiates a spray of disinfectant onto the stethoscope’s membrane. Hackbarth has already filed a patent application for her invention. She has also found an investor who would like to further develop the self-disinfecting stethoscope and make it commercially viable.3

Hackbarth is in good company with her efforts for better stethoscope hygiene. Jürgen L. Holleck from the Yale University School of Medicine (New Haven, Connecticut, USA) also developed and tested various quality improvement measures for stethoscope hygiene4, such as the use of alcohol swabs, alcohol gels and disinfectant wipes after patient examinations. Furthermore, he informed other stethoscope-users about the significance of these measures and has evaluated their reactions. His aim is to integrate disinfection of stethoscopes into hygiene plans so that the devices can continue to be used without risk in outpatient care.

During the test period: auscultation via radar

Modern medicine offers another solution that makes manual monitoring unnecessary, and which is currently being tested at the University of Erlangen-Nuremberg5: auscultation via radar. With this method, the examination is completely contact-free, which excludes the transmission of germs. Initial experiments with test persons were very promising. However, the radar system will not replace stethoscopes in the near future. Doctors do not want to part with their stethoscopes for several reasons. “The stethoscope is still very important in the daily life of a general practitioner. I need it a dozen times over every day,” states Dr. Frauke Gehring in a DocCheck article6 Gehring, a private practitioner of internal medicine in Arnsberg, Germany, regularly listens to breathing sounds to diagnose bronchitis, pleurisy, asthma or pneumonia. Heart sounds can tell her about arrhythmias and valve defects or give her clues about pericardial inflammation or narrowed carotid arteries. Finally, she regularly needs the stethoscope to measure blood pressure. The use of imaging techniques is important, but only a supplement. In her opinion, the radiation exposure of the non-contact method is too high for patients long term. And the costs for X-rays are also considerably higher. She believes radar devices should only be used if they are absolutely necessary and provide additional benefits.

Even if modern techniques and devices are available today that could replace the stethoscope, it remains one of the most important medical instruments for the correct diagnosis of many diseases. Taking on board the Robert-Koch-Institute (RKI) requirement that “all devices/medical devices in direct contact with the patient […] must be disinfected after use or before application to another patient”, its use is still recommended7. This means that users must be aware of the risk of infections, and then prevent these by taking appropriate hygiene measures.

Further information

  1. press release, Jugend forscht
  2. Contamination of Stethoscopes and Physician’s Hands After a Physical Examination, Mayo Clinic Proceedings, March 2014.
  3. Jugend forscht, Hamburger Abendblatt.
  4. Can education influence stethoscope hygiene? American Journal of Infection Control, 2017.
  5. Radar-Based Heart Sound Detection, Nature, Scientific Reports, 2018.
  6. Stethoskop: Gerät oder Geschmeide?, DocCheck
  7. Empfehlungen des Robert Koch Institutes zu Präventions- und Kontrollmaßnahmen, RKI
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