Stethoscopes are an essential tool in many medical professions. They are one of the first tools used to assess patients’ blood pressure, heart, and lungs. As commonplace as stethoscopes are, they seem to be everywhere. Sitting on the shelf in every doctor’s office, it’s easy to forget how complex stethoscopes are.
If you need help finding a stethoscope to fit your needs, check out our article on the best Littmann Stethoscopes.
Contents
How Stethoscopes Work
The part of the stethoscope that touches the patient is a sealed membrane known as the diaphragm. When in use, it transfers sound waves from the body to the air inside the stethoscope tube. The long, narrow tube effectively amplifies the body’s sounds as they travel to the ear tip, where they are heard by the doctor.
How to Operate a Stethoscope
- Wearing it - The ear tips should be twisted in order to seal the ear. When done right, the tips will point towards the nose, and outside noises should become softer.
- Holding it - The chest piece should be held in your dominant hand, between the index and middle fingers, just above the knuckle. To prevent interfering noise, curl the thumb under the tube to keep it still.
- Placing it - The stethoscope should ideally be placed right against the skin, or at most one layer of clothing apart if necessary.
What a Stethoscope Can Do
1. Measure blood pressure
Though this may be the most popular use of a stethoscope, it can easily be done incorrectly. As a blood pressure cuff is inflated around the upper arm, the stethoscope is used to listen for audible heartbeats right below the cuff, at the brachial artery.
The two numbers that make up a blood pressure reading, systolic and diastolic pressure, are read from the dial when 1. the Korotkoff sounds are first heard and 2. when the volume of the Korotkoff sounds drop drastically. Many are taught to read diastolic pressure when the sound stops- this is not advised, as it leads to a diastolic pressure that is too low.
2. Identify lung sounds
When used on the chest and back, stethoscopes can check for proper breathing, and identify any airway blockages or lung inflammation.
A complete lung checkup includes listening to six chest “paired areas” and seven back “paired areas”. The benefit of checking paired areas, or identical spots on the left and right side of the body, is that the lungs can be directly compared to each other. When done this way, it becomes much easier to detect any abnormalities.
For the most accurate listening, the patient should be leaning forward during the back examination. For both chest and back, doctors should start above the clavicle and work their way down, one paired area at a time.
3. Identify heart sounds
Besides checking for heart rate, stethoscopes can alert doctors to dangerous “gallops” or “murmurs” in the heartbeat. While these can be hard to detect, listening to enough hearts over time will make any irregular sounds more apparent. A complete heart checkup includes listening to four main areas around the heart, which each correspond to one main heart valve.
- Left of sternum, 2nd rib down- pulmonic valve
- Right of sternum, 2nd rib down- aortic valve
- Left of sternum, 4th rib down- tricuspid valve
- In line with left nipple, 5th rib down- mitral valve
4. Identify bowel sounds
Checking for abnormal bowel sounds is quite simple, but important in cases of possible bowel obstructions or paralytic ileus . Loud bubbling or gurgling sounds, known as borborygmi, are generally harmless and can usually be ignored.
5. Detecting abnormal blood flow (bruits)
A bruit is a distinct, “whoosh”-type sound that is a clear indicator of vascular problems. Bruits usually suggest that the artery in question is narrower than usual, which can be a sign of dangerous conditions such as arteriosclerosis or aneurysms. Arteries where bruits are usually detected:
- Carotid (neck)
- Abdominal aortic
- Renal (kidney)
- Femoral (thigh)
- Iliac (pelvis)
- Temporal (forehead)
6. Measuring the size of the liver
Though this procedure is uncommon, a stethoscope can help measure the vertical length of the liver at the nipple line.
With the stethoscope placed beneath the right nipple, the index finger should be placed directly in the nipple line, down at belt level. By gently scratching the skin as the finger works its way up the nipple line, the stethoscope will yield a much duller sound than usual while the finger is over the liver.
Marking the beginning and ending points at which said dullness is heard yields a fair approximation of the liver length at the nipple line. A measurement of around 10 cm is considered normal.
7. Hearing aid for physician-patient communication
In situations where patients have poor hearing, doctors can let the patient wear the stethoscope. By talking through the chest piece, doctors can use it as a make-shift hearing aid.
Which side to use?
The diaphragm (larger) side is ideal for detecting breathing, as well as normal heart rhythms.
The bell (smaller) side is better for detecting abnormal heart sounds and bruits, as well as bowel sounds.
A cardiac exam should begin with use of the diaphragm, followed by use of the bell.
Upkeep/Safety
Stethoscopes require frequent cleaning to ensure patient safety. The chest piece should be cleaned and disinfected with alcohol before each use.
Additional Resources
Stethoscopes Theory
There already exists an incredible amount of high-quality information on how to use stethoscopes, so rather than reinvent the wheel, we made an easy-to-use database that helps you find the best information. Just follow the links to find infographics, audio-visual aids, and interactive quizzes.
How Stethoscopes Work – A nice overview of the different parts of a stethoscope, how to hold it, what you can do with it, along with some tips and tricks.
Listening to Body Sounds
Pulse and Blood Pressure
Taking Vitals with a Stethoscope – How to use a stethoscope to measure blood pressure and the science behind Korotkoff sounds.
Heart
- Where to Auscultate – A poster that shows the different locations to auscultate to listen for heart sounds.
- Heart Sounds with EKG Visual – A list and description of heart sounds along with sound and an EKG visual.
- Explanation of Heart Sounds and Their Origins – Nine videos from Khan Academy on heart disease, heart sounds, murmurs, and other irregularities.
- Heart Sound Quiz – Choose the drill, listen to the sounds, and identify them. Four, 30-minute drills with the option to print a certificate of completion if you register. Can be used as continuing education credit for EMTs.
Lungs
- Where to Auscultate – A poster that shows where to place a stethoscope to listen for lung sounds.
- Lung Sounds with Visual Plus Quiz – A course on basic lung sounds that includes a quiz at the end. Printable certificate available if you register. Can be used as continuing education credit for EMTs.
- 3M Littmann Stethoscope Basic Lung Sounds Tutorial with Quiz – Similar course where you can listen to lung sounds and answer a quiz at the end.
Bowels
Assessing bowel sounds with a stethoscope has low accuracy, and treatment decisions should not be based solely on auscultation[1].
- Bowel Sounds with List of Sample Cases – Sample cases of bowel distress with sounds for all four abdominal quadrants.
Comparison of Littmann Stethoscopes
We compared the Littmann stethoscopes currently available on the market to help you decide which one is best for you. For more information read our article: The Best Littmann Stethoscopes - Comparison Guide
References
- Breum, Birger Michael, et al. "Accuracy of abdominal auscultation for bowel obstruction." World Journal of Gastroenterology: WJG 21.34 (2015): 10018.
