The stethoscope is an instrument used for auscultation, or listening to sounds produced by the body. It is used primarily to listen to the lungs, heart, and intestinal tract. It is also used to listen to blood flow in peripheral vessels and the heart sounds of developing fetuses in pregnant women.
A stethoscope is used to detect and study heart, lung, stomach, and other sounds in adult humans, human fetuses, and animals. Using a stethoscope, the listener can hear normal and abnormal respiratory, cardiac, pleural, arterial, venous, uterine, fetal and intestinal sounds.
All health care providers and students learn to use a stethoscope.
Stethoscopes vary in their design and material. Most are made of Y-shaped rubber tubing. This shape allows sounds to enter the device at one end, travel up the tubes and through to the ear pieces. Many stethoscopes have a two-sided sound-detecting device or head that listeners can reverse, depending on whether they need to hear high or low frequencies. Some newer models have only one pressure-sensitive head. The various types of instruments include: binaural stethoscopes, designed for use with both ears; single stethoscopes, designed for use with one ear; differential stethoscopes, which allow listeners to compare sounds at two different body sites; and electronic stethoscopes, which electronically amplify tones. Some stethoscopes are designed specifically for hearing sounds in the esophagus or fetal heartbeats.
Stethoscope users must learn to assess what they hear. When listening to the heart, one must listen to the left side of the chest, where the heart is located. Specifically, the heart lies between the fourth and sixth ribs, almost directly below the breast. The stethoscope must be moved around. A health care provider should listen for different sounds coming from different locations. The bell (one side of the head) of the instrument is generally used for listening to low-pitched sounds. The diaphragm (the other side of the head) of the instrument is used to listen to different areas of the heart. The sounds from each area will be different. "Lub-dub" is the sound produced by the normal heart as it beats. Every time this sound is detected, it means that the heart is contracting once. The noises are created when the heart valves click to close. When one hears "lub," the atrioventricular valves are closing. The "dub" sound is produced by the pulmonic and aortic valves. Other heart sounds, such as a quiet "whoosh," are produced by "murmurs." These sounds are produced when there are irregularities in the path of blood flow through the heart. The sounds reflect turbulence in normal blood flow. If a valve remains closed rather than opening completely, turbulence is created and a murmur is produced. Murmurs are not uncommon; many people have them and are unaffected. They are frequently too faint to be heard and remain undetected.
The lungs and airways require different listening skills from those used to detect heart sounds. The stethoscope must be placed over the chest, and the person being examined must breathe in and out deeply and slowly. Using the bell, the listener should note different sounds in various areas of the chest. Then, the diaphragm should be used in the same way. There will be no wheezes or crackles in normal lung sounds.
Crackles or wheezes are abnormal lung sounds. When the lung rubs against the chest wall, it creates friction and a rubbing sound. When there is fluid in the lungs, crackles are heard. A high-pitched whistling sound called a wheeze is often heard when the airways are constricted.
When the stethoscope is placed over the upper left portion of the abdomen, gurgling sounds produced by the stomach and small intestines can usually be heard just below the ribs. The large intestines in the lower part of the abdomen can also be heard. The noises they make are called borborygmi and are entirely normal. Borborygmi are produced by the movement of food, gas or fecal material.
Some stethoscopes must be placed directly on the skin, while others can work effectively through clothing. For the stethoscopes with a two-part sound detecting device in the bell, listeners press the rim against the skin, using the bowl-shaped side, to hear low-pitched sounds. The other flat side, called the diaphragm, detects high-pitched sounds.
A stethoscope is used in conjunction with a device to measure blood pressure ( sphygmomanometer ). The stethoscope detects sounds of blood passing though an artery.
Examination with a stethoscope is noninvasive but very useful. It can assist members of the health care team in localizing problems related to the patient's complaints.
Stethoscopes should be cleaned after each use in order to avoid the spread of infection. This precaution is especially important when they are placed directly onto bare skin.
A stethoscope is a sensitive instrument. It should be handled with some care to avoid damage. It requires periodic cleaning.
There are no risks to persons being examined with a stethoscope. Users of a stethoscope may be exposed to loud noise if the bell is accidentally dropped or struck against a hard surface while the earpieces are in the user's ears.
Stethoscopes produce important diagnostic information when used by a person with training and experience.
Morbidity and mortality rates
Normal use of a stethoscope is not associated with injury to either an examiner or a person being examined.
A tube formed by a roll of paper will function in the same manner as a stethoscope. This improvised instrument was the first form of the modern stethoscope invented by René Laënnec (1781-1826), a French physician. An inverted glass will also function as a stethoscope by placing the open portion on the surface to be listened to and the ear of the examiner on the bottom of the glass. Due to their shape, wine glasses with stems are more effective than flat-bottomed tumblers.
See also Physical examination .
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Blaufox, MD. An Ear to the Chest: An Illustrated History of the Evolution of the Stethoscope . Boca Raton, FL: CRC Press-Parthenon Publishers, 2001.
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Guinto, C. H., E. J. Bottone, J. T. Raffalli, et al. "Evaluation of Dedicated Stethoscopes as a Potential Source of Nosocomial Pathogens." American Journal of Infection Control 30 (December 2002): 499-502.
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American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (913) 906-6000. http://www.aafp.org . E-mail: email@example.com
American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 434-4000; FAX: (847) 434-8000. http://www.aap.org . E-mail: kidsdoc @aap.org
American College of Physicians. 190 N. Independence Mall West, Philadelphia, PA 19106-1572. (800) 523-1546, x2600 or (215) 351-2600. http://www.acponline.org .
American College of Surgeons. 633 North St. Clair Street, Chicago, IL 60611-3231. (312) 202-5000; FAX: (312) 202-5001. http://www.facs.org . E-mail: firstname.lastname@example.org
British Broadcasting Company. http://www.bbc.co.uk/radio4/science/guessingtubes.shtml . (March 1, 2003)
Institution of Electrical Engineers. http://www.iee.org/News/PressRel/z18oct2002.cfm . (March 1, 2003)
McGill University Virtual Stethoscope. http://www.music.mcgill.ca/auscultation/auscultation.html . (March 1, 2003)
University of Minnesota Academic Health Center. http://www.ahc.umn.edu/rar/MNAALAS/Steth.html . (March 1, 2003)
L. Fleming Fallon, Jr., MD, DrPH
WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?
Any member of a health care team participating in a physical examination uses a stethoscope. It is used to detect and transmit sounds created within the body.
QUESTIONS TO ASK THE DOCTOR
- Are the sounds being heard normal or abnormal?
- Have the sounds changed since the last examination?
- Has a murmur, if present, changed in pitch or loudness?