It’s practically the symbol of physicians and physician assistants. Most of us know the basics: you put the things in your ears, the other end on a sick person, and listen. But stethoscopes can do much more. The following are a few facts about the tool, followed by a more complete list of its uses. If you’re new to the medical field, getting comfortable with your stethoscope will make you a better student and clinician of medicine.
Origin. Early stethoscopes were little more than “ear tubes,” that were invented in 1816 by René Laennec at the Necker-Enfants Malades Hospital in Paris, France. They were updated here and there, but current designs are credited to Dr. David Littman of Harvard University who made them lighter and gave them better acoustics.
Auscultation: the act of listening for sounds within the body. Latin auscultation-, auscultatio, act of listening, from auscultare to listen.
Parts. Even modern scopes are fairly simple (except the electronic ones that digitally amplify sound). The following diagram will provide you with the important vocabulary:
The most important parts to know are the diaphragm, which is larger, flatter side of the chest piece, and the bell, which has the smaller, concave piece with a hole in it. Switch between the two by twisting the chest piece 180 degrees. You’ll hear a click. Then tap each side to see which one is “on.”
How it works. The diaphragm is a sealed membrane that vibrates, much like your own eardrum. When it does, it moves the column of air inside the stethoscope tube up and down, which in turn moves air in and out of your ear canal, and voila, you hear sound. Since the surface area of the diaphragm is much greater than that of the column of air that it moves in the tube, the air in the tube must travel more than the diaphragm, causing a magnification of the pressure waves that leave the ear tip. In your ear, larger pressure waves make louder sounds. This is how stethoscopes amplify sounds.
How to wear it. Place the ear tips in the ears, and twist them until they point slightly forward (toward your nose). If you do it right, you’ll make a good seal, and sounds in the room will become very faint.
Holding it. The important tip here is that in most cases you’ll want to hold the chest piece between the distal part of your index and middle finger on you dominant hand. This grip is better than using your fingertips around the edge of the diaphragm/bell because it allows you to press against the patient without your fingers rubbing it and creating extra noise. A gentle touch is best.
Placing it. Place the chest piece (diaphragm or bell) directly against skin for the best sound transmission. If you’re in a hurry you can hold it over one thing layer of clothing, such as a T-shirt, but this isn’t recommended, as doing so risks missing nuances that might be crucial.
What you can do with it: If you learn the following, you’ll be using yours more than 90% of clinicians. The links will take you to free pages on the specific technique.
Diaphragm vs. Bell. The diaphragm is best for higher pitched sounds, like breath sounds and normal heart sounds. The bell is best for detecting lower pitch sounds, like some heart murmurs, and some bowel sounds. It is used for the detection of bruits, and for heart sounds (for a cardiac exam, you should listen with the diaphragm, and repeat with the bell). If you use the bell, hold it to the patient’s skin gently for the lowest sounds, and more firmly for the higher ones.
Which one should I buy? Plan on spending no less than $60 for a quality stethoscope. Cheaper ones can work alright, but aren’t as durable, and have weaker sound profiles. The standard by which all others are measured is generally accepted to be the 3M Littman Cardiology III. Don’t spend gobs of money on a digital unless you know you will be working in cardiology – and maybe not even then. To see our stethoscope recommendations, visit stethoscope buyer’s guide page.
Infection control. Clean your stethoscope regularly, particularly the chest piece. Studies have found that stethoscopes are frequently the vectors for patient-to-patient disease transmission. Just wipe the chest piece with an alcohol prep pad to disinfect.