The stethoscope has served as an icon of the medical profession since the 1940s, when its modern design was cemented by inventors at Hewlett Packard. While the device allows doctors to discover life-threatening heart conditions before they become fatal, it can also act as a vector for disease, according to several recent studies. However, even 20 years ago, the fact that the stethoscope served as a mobile petri dish for bacteria was of little concern. Antibacterial compounds kept any problematic strains in check. These days, however, antibacterial-resistant bacteria like MRSA can prove fatal if they gain access to a patient’s bloodstream.
Consequently, doctors the world over are sterilizing their stethoscopes more than ever. In fact, current guidelines instruct doctors to sterilize their tools after each patient. Unfortunately, this is simply not practical in high-volume areas such as emergency rooms. Worse yet, emergency rooms exhibit the highest concentrations of bacteria.
Research has found that the stethoscope diaphragm—the plastic or epoxy disk that detects high frequency sounds—can harbor more bacteria than a doctor’s palms. The diaphragm picks up bacteria from a patient’s skin where it subsists on oils deposited there. When the diaphragm comes into contact with the next patient, some of the bacteria jump ship. As patients leave the hospital, they then spread these resistant bacteria to the general population.
Dr. Didier Pittet of the University of Geneva Hospitals in Switzerland stresses that bacteria transfers like this are occurring at all hours of the day, every day of the year. Because bacteria evolve at a much higher rate than do larger animals, strains of resistant bacteria can spring up at any time. A worldwide pandemic of such bacteria could render a gash or flesh wound a life-threatening condition. Such wounds, interestingly, are why pre-industrial man rarely lived past the age of 45.
Additionally, the paper “The Stethoscope: Potential Source of Nosocomial Infection,” published in JAMA Internal Medicine and written by Mark A. Marinella, stresses that antibacterial-resistant bacteria can also live on a stethoscope’s tubes. These surfaces are not sanitized as frequently as the diaphragm, and a doctor can unwittingly transfer bacteria from them back to the diaphragm itself. The study also found that eleven species of bacteria typically infect stethoscopes, and that staphylococcus is likely present on 100% of stethoscopes worldwide. The more dangerous Staphylococcus aureus was found on 38% of tested stethoscopes.
Several doctors have sought to stave off disaster. Dr. Sergio Sanchez-Zambrano, for instance, created a disposable diaphragm cover that keeps bacteria out without significantly hampering audio fidelity. Doctors will still have to sterilize their stethoscopes frequently, but between patients they can simply slip on a new disposable cover.
Meanwhile, Dr. Robert F. Stickley has pioneered an inexpensive diaphragm sanitation system. His device is an attachment that fits over the diaphragm and bell when the stethoscope is not in use. The attachment contains replaceable antibacterial pads, which keeps the stethoscope’s business end sanitary between uses.
Innovations like these will allow doctors to continue to treat patients with the stethoscope for decades to come. Eventually, affordable versions of hand-held ultrasound devices will become available, and these devices will have far less potential to spread pathogens. Still, many experts believe that the stethoscope will remain essential in emergency rooms or in situations in which power must be rationed.