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The Steth IO: 3D Printed iPhone Case

The Steth IO, created by teenage inventor Suman Mulumudi, promises to revolutionize the stethoscope market with a powerful combination of a highly versatile—and relatively inexpensive—stethoscope embedded into an iPhone case and powerful processing software. The inventor’s father, himself a cardiologist, has formed a company around the idea. That company, StratoScientific, is currently seeking FDA approval for the invention. Yet as the device steps onto the stage of public scrutiny, many find themselves wondering whether the device can live up to the company’s’ claims.


The Diaphragm

Suman Mulumudi created his plastic diaphragm by connecting it to the iPhone case via a series of very small plastic tubes. According to the 15-year-old Mulumudi, previous inventors failed to create a working stethoscope iPhone case because they were merely placing a highly-sensitive microphone over the skin. Such an approach fails, however, because the open air is a poor conductor of the faint sounds produced by the heart and cardiovascular system. The system of tubes in Mulumudi’s design mimics those used in actual stethoscopes by trapping air within them. The narrow tubes, with their air pockets, provide a buffer against outside sounds and at the same time ferry the faint heart sounds to the iPhone’s microphone. An on-board app then analyzes the sounds. Mulumudi produced the first version of the Steth IO using a MakerBot 3D printer.


To get FDA approval, StratoScientific will have to demonstrate that the Steth IO—and the app that goes with it—can accurately capture heart sounds and interpret them. The iPhone app the company has produced interprets the sounds gleaned by the diaphragm and produces both auditory and visual feedback. One potential snag is that because the diaphragm is made of plastic, it may pick up quite a bit of background noise. This background noise would then have to be filtered out by the iPhone app. If, however, even some of this ambient noise is considered germane by the app, a doctor would not be able to trust its readout. The case itself provides a buffer against ambient noise, but compared to the shielding found in a standard stethoscope, it may prove insufficient.


StratoScientific makes several claims with regards to the new stethoscope—specifically, that it can be produced for less than a standard stethoscope. This is especially true as the cost of 3D printers and raw materials goes down. The company also claims to have developed software that displays cardiovascular sounds in much the same way as an ECG does. If proven reliable, this technology will dramatically reduce the cost of such tests. StratoScientific has also claimed that doctors will be able to diagnose heart murmurs “with ease.” It is important to note, however, that a heart murmur is merely an irregular sound that occurs between the two pulses of the contracting heart, namely S1 and S2. Murmurs are caused by any number of issues, from torn heart muscle to malformed heart valves. Generally, the stethoscope detects the murmur, and the doctor determines its significance, if any.

The company is on firmer ground with its claim that the software that drives the Steth IO allow doctors to store and retrieve heart data for individual patients via electronic medical records. These secure records are stored remotely in the cloud, allowing practitioners access to a patient’s medical history in minutes.

Some wonder, however, if patients will feel comfortable with a doctor’s smartphone pressed against their chest. After all, people tend to keep these devices on their person at all times, often in a pocket. Standard stethoscopes can harbor infectious microbes and are sterilized often as a result. If the StethIO cannot be sterilized in the same way, microbial proliferation may be a problem. This is likely to be a factor for FDA consideration as doctors may not be willing to remove their smartphone case several times per day.

StratoScientific is seeking funding for their device and points out that the consumer medical device market will be worth over $10.9 billion by 2017. The global stethoscope market itself is estimated to be at $300 million by the same year. Time will tell, however, whether the Steth IO is sensitive enough to be of any actual use. Even if it is, many doctors may refuse to adopt the device in favor of the proven stethoscope designs from Littmann and other major manufacturers.

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