Developing a 21st-century Stethoscope

What is undoubtedly the most symbolic item for a medical professional—physician, nurse, clinician—is the stethoscope. The instrument has been around for nearly 200 years, and while there have certainly been developments during that period of time, the ear tips, tubes, and chest piece have pretty much become a standard form factor for recent history.

Which gives rise to an interesting aspect of the development of a brand-new stethoscope, the Model 3200, by 3M Littmann (littmann.com). Although this stethoscope has advanced features for auscultation—that’s what a stethoscope is used for, listening to the sounds from within a body, such as those from the heart and lungs—according to Craig Oster, Product Development manager for Littmann, “We work a lot with our customers—physicians and nurses—to optimize the user interface, to make it as simple as possible, because our goal is not to change the work flow. We don’t want it to change anything they’re doing. We want it to sound the same as what they’re familiar with. We didn’t want them to have to change their skills. They should practice as they always practice.”

Not only is he talking about the activities that they perform during an examination, but what they’ve learned. During medical training, they learn the various sounds from the heart and lungs. They learn what’s normal and what’s abnormal. And they learn what the pathologies or disease states that an abnormal sound represents. So when they use a stethoscope to listen to a patient, they have a mental file cabinet that contains representations of what sounds good, what doesn’t and what it means.

The Model 3200 is an electronic stethoscope. It may seem somewhat natural that what started as a pure acoustical instrument in the 19th century would become electronic in the 21st century. And while this is not the first electronic stethoscope from 3M Littmann (they’ve been making them since 2000, an analog unit) nor from other medical instrument companies, they did work to address some issues related to the forerunners, part of which had to do with what was being heard.

To apply advanced technology—such as digital signal processing—to the stethoscope without taking into account the actual practice of those using the instrument would be of little advantage to anyone involved, medical professional and patient alike. It’s one thing for some things to be dropped from an MP3 file that you’re listening to, but something else entirely for there to be a change in what is heard through the ear tips of a stethoscope.

There was another aspect that led to the development of the Model 3200, one that is broader in context. There is a burgeoning aspect of clinical medicine called “telemedicine.” According to the American Telemedicine Association (americantelemed.org), “Telemedicine is the use of medical information exchanged from one site to another via electronic communications to improve patients’ health status.” And according to figures cited by 3M Littmann from Global Industry Analysts (strategyr.com), the telemedicine industry had sales of $7.9-million in 2009 and is expected to reach sales of $18.4-billion by 2015.

Todd Schwarzenbach, Global Business manager for 3M Littmann explains that “telemedicine involves geographically separated people—in the same building or elsewhere—that allow the doctors or nurses at either end to act as if they’re both there real-time with a patient.” For example, a general practitioner may want to bring in a cardiologist for a consultation, but the heart specialist may be in a clinic on the other side of town (or further, for that matter).

So they’ve developed the “Scope-to-Scope Tele-Auscultation System” that can be used with the Model 3200, a software system that allows clinicians to digitally transfer captured patient sounds in real time from one Model 3200 to another. The Model 3200 is Bluetooth-enabled so that the transfer is performed easily. Again, it is about not changing what the practitioners do in the performance of their duties.

Yes, the medical professionals at either end of this physical/virtual consult are both employing the Model 3200 stethoscopes. The setup, explains Curt Morgan, who was software development lead on the project, is that there are PCs running the software on either end. They are networked via the Internet or a VPN. So the doctor with the patient moves the chest piece around as she would normally do, the digital signal is encapsulated, then sent to the remote physician with the other stethoscope. “There are a lot of quality of service metrics built into the software to ensure that the data sent across the Internet is identical at both ends. We make it visible in an easy-to-use interface for the physician: They see a green status indicator on the screen of the PC for 100%.”

Why is the physician on the receiving end using a stethoscope? “The reason we’re not pushing that sound through the PC speakers is because speakers vary from computer to computer, and they’re often not capable of reproducing the frequency range that the stethoscope can,” Morgan answers.

Schwarzenbach adds, “By having the ear tips in their ears, we’re trying to make the experience for the doctor as similar as possible as if they were there in person with the patient.”

One feature that’s part of the telemedicine package that was developed as a result of the product developers at Littmann observing doctors, nurses and clinicians in action allows communications through the Model 3200. The person at the remote end talks into the chest piece and is heard through the ear tips of the other person. In previous setups it was necessary to remove the stethoscope to communicate—say by using the camera/speaker setups on the PCs. “We also know that sometimes the physicians on both ends may want the ability to exchange information without alarming the patient.”

There are various features of the Model 3200 that provide benefits to the user. They include proprietary ambient noise reduction technology that reduces background noise by 85% without affecting the body sounds (think about all the noise in a busy clinic or ER); soft, acoustic sealing eartips; up to 24X sound amplification; the ability to record 12 tracks; and instant-on (Oster: “Physicians don’t want to have to turn on a stethoscope—especially if the patient is crashing or it’s an emergency.” So the stethoscope is turned on in the morning, and then remains on as long as it is used periodically. As soon as the chest piece touches the patient, it is fully activated. The Model 3200 runs on a single AA battery.)

This leads to a consideration of the make up of the product development team at 3M Littmann for electronic products such as the Model 3200. “It’s changed the technical skills required on the product development side. The traditional mechanical stethoscope required good knowledge in mechanical design, materials, and acoustics. The electronic stethoscope, which gets into the world of connectivity, means not only do we need mechanical design, materials, and acoustics, but digital signal processing, software design and development, and wireless communications.”

But while the make up of the product development may change, the commitment to helping medical professionals help their patients remains the same.