The stethoscope has changed little in design since its inception in the early 1970s. While the device was technically invented in France in the late 19th century, it was greatly improved by Dr. David Littmann. Dr. Littmann, a Harvard professor, was able to obtain sound quality never before achieved by incorporating a tunable diaphragm into the design of the classic stethoscope. This innovative design places the bell and the diaphragm on the same side of the chestpiece, minimizing the amount of effort required to get both readings.To switch between the diaphragm and bell, the clinician simply varies the amount of pressure they place on the skin.
The tubes that channel amplified sound from the body into the ears have also undergone significant improvement over the years. Today’s stethoscope features two tubes, while the first stethoscope was comparably quite primitive. This stethoscope, designed by Dr. René Laennec of France in the late 19th century, featured a single wooden tube. Today’s tubes are latex free because some patients—humans and animals—suffer skin irritation when they come into contact with the material.
Modern stethoscopes are capable of recognizing very specific sounds within the chest cavity, and they can aid doctors in diagnosing serious heart and lung issues. Many of these maladies, if undetected, can lead to sudden death later in life. However, as sophisticated as the stethoscope is, it has one shortcoming: it gives no visual feedback. While inventors are working feverishly to correct this issue by creating apps and new interfaces for traditional stethoscopes, there is an existing technology that’s providing doctors with an unparalleled window into a patient’s body.
Ultrasound describes a range of sound that is too high in frequency for humans to detect. This threshold varies from person to person, but it is generally found at around 20 kHz. Ultrasound devices operate by sending oscillating sound waves through solid objects and interpreting the data that returns. From this, they can discern the size, shape and distance of individual body parts. Some ultrasound devices are capable of rendering 3D images. Some operate at around 20 kHz, while others operate into the gigahertz.
At around 3 GHz, ultrasound resolution approaches that of high-end digital cameras. It’s important to note, however, that ultrasound images are generally monotone. Nonetheless, doctors can use these high-resolution images to view organs such as the heart without disturbing them. Combined with a stethoscope, handheld ultrasound wands could one day allow doctors to diagnose murmurs and other potentially-deadly heart conditions on the spot, bypassing time-consuming electrocardiogram analysis.
Tunable handheld ultrasound devices could be used to view organs as a whole, as well as view individual structures within those organs at the turn of a knob. These devices will operate at less than 1 W/cm2 in order to avoid burning the tissue under examination. Basic versions of the technology are currently available as point-of-care ultrasound devices, and they are commonly used in conjunction with the stethoscope. In the future, however, the stethoscope as it is known today could be incorporated into these devices, providing doctors with a single go-to tool with which to view and hear internal body structures. The advantage that this technology will impart cannot be understated.
For instance, doctors traditionally diagnose pneumonia by listening to the breathing patterns of an afflicted individual. However, this examination is extremely difficult to carry out on children as they tend to squirm. With an ultrasound stethoscope, a clinician could check the lungs for visual signs of inflammation, and if found, they could listen to the breathing as a secondary step. Visual confirmation of inflammation in the lungs could cut hours off of the diagnostic process, which could translate into thousands of lives saved per year.
According to Scott D. Solomon, MD of Harvard Medical School, ultrasound technology represents a radical departure from traditional diagnostic tools, and it should therefore receive individual attention in the curriculum. All that remains to be seen is whether the traditional stethoscope will remain the doctor’s standby or if ultrasound technology will supersede it entirely.