Definition

The stethoscope is an instrument used to listen to sounds produced by the body. It is used to listen to the lungs, heart, and intestinal tract.

Purpose

A stethoscope is used to detect and study heart, lung, stomach, and other sounds in humans and animals. Using the stethoscope, the listener can hear abnormal respiratory, cardiac, pleural arterial, venous, uterine, fetal, and intestinal sounds.

Description

Stethoscopes vary in their design and material. Most are made of rubber tubing, shaped in a "Y," allowing sound 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, which listeners flip, depending on whether they need to hear high or low frequencies. However, some of the newer models have one pressure-sensitive head. The various types of stethoscopes include: binaural stethoscopes, designed for use with both ears; single, designed for use with one ear; differential, with which listeners can compare sounds at two different body sites; and electronic, which electronically amplifies tones. Some stethoscopes are designed specifically for hearing the fetal heartbeat or esophagus.

Operation

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 at the end, 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.

Maintenance

In order to avoid the spread of infection, stethoscopes should be cleaned after each use—especially when placed directly on the patient's skin.

Health care team roles

Everyone on the health care team uses a stethoscopea, as the provider may need to listen to sounds produced by the heart, lungs, stomach, or another body organ often.

Training

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, it is between the fourth and sixth ribs, almost directly below the breast. The stethoscope must be moved around; the health care provider should listen for different sounds emanating from different locations. The bell of the instrument—generally used to listen to sounds of low pitch, and then its diaphragm—should be used to listen to different areas of the heart. The sounds will be different. "Lub-dub" is the sounds produced by the normal heart. Every time this sound is detected, it means that the heart is contracting one time. The noises represent the heart valves clicking to close. When one hears "lub," the atrioventricular valves are closing, and "dub" means the the pulmonic and aortic valves. Other heart sounds, such as the quiet "whoosh," heard after "lub-dub," reflect the existence of a "murmur." These are heard when the blood moves through the heart, and mean that there is "turbulence" in the blood flow. If a valve remains closed, rather than opening completely, one might hear a murmur. These are not at all uncommon; in fact, many people have them and are unaffected.

The lungs and airways require different listening skills than those used to detect heart sounds. The stethoscope must be placed over the chest, and the patient must breathe in and out deeply, and slowly. Using the bell, the different sounds should be noted 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. When performing "percussion," on the chest, the health care practitioner should be listening for sounds made by sounds the patient makes. One would lightly "thump" around the stethoscope, against the chest, with one finger. Lungs that sound hollow are normal; they have no air in them. Lungs that have a more solid sound appear dead. On percussion, this "dead" sound may be solidification of the lung. In this case, one might make an initial diagnosis of pneumonia.

When crackles or wheezes are detected, the practitioner is hearing lung sounds that are abnormal. When the chest wall is being rubbed by the lung, "friction rubs" are detected. When there is fluid in the lungs, crackles will be hard. This is often heard when the patient has pneumonia, or pulmonary edema. A high-pitched whistling sound (a wheeze) is often heard when there is pneumonia, or when an airway disease (like bronchitis) is present. Lastly, an infection between the lung and the chest might produce the friction rubs—squeaky noises that infections like pleuritis (an infection between the lung and chest wall) produce.

To listen to the abdomen, the stethoscope should be held over its upper left side. One can hear "gurgling" just under the ribs. The intestines, in the lower part of the abdomen, can also be heard. The noises they make are "borborygmus"—and they are normal. The abdomen is also a site where percussion can be heard. If one thumps all around the bell of the stethoscope, the individual will hear a solid sound, as if the organ is "dead." When the sound is hollow, it means that the intestinal tract has gas in it.

Despite these somewhat basic instructions, it takes experience and skill to determine what tests might be needed once examination with the stethoscope has been completed. Examination with this instrument is particularly noninvasive, but useful. It can assist the physician and health care team in localizing the problem about which the patient is complaining.