Beaumont, C. Estelle MS, PhD
ONCE A MAJOR STATUS SYMBOL, bandage scissors have been replaced by latex-free stethoscopes color coordinated to reflect your personality or to coordinate with the colors of your favorite scrubs. But there's more than fashion to consider when selecting this important assessment tool. In this article, I'll review features, functions, and price ranges for the two major categories of stethoscopes: acoustic and electronic. Although acoustic stethoscopes are by far the most common, you'll be seeing more electronic stethoscopes in use as prices and weight decrease.
Sounding out acoustic stethoscopes
The acoustic properties of stethoscopes vary considerably. Many factors besides your own hearing ability affect what sounds you hear. And almost as important as hearing the sounds that come from the patient's body is not hearing ambient sounds that keep you from focusing on physiologic sounds. The overall design of the stethoscope head, tubing, and ear tips contributes to acoustic performance.
Acoustic stethoscopes, available in an array of colors, consist of ear tips (also called earpieces), binaurals (the curved metal pieces that connect the ear tips and tubing), tubing, and a head or chest piece (usually a diaphragm, but sometimes a combination bell and a diaphragm). Let's take a closer look at each component.
* Ear tips are available in hard and soft materials; some stethoscopes come with extras of both types. Check which type conforms best to the unique shape of your ear canals to keep out the extraneous noises of your busy medical/ surgical unit. Make sure the ear tips are easy to remove for cleaning and replacement.
* Tubing in stethoscopes is normally about 26 to 28 inches (65 to 70 cm) in length, but longer tubing is available and can be useful in some situations.
The tubing might consist of two tubes side by side or one large tube with two channels inside. The lumen of each tube should be at least 1/8 inch.
The single tube creates less ambient noise than two tubes rubbing together. Make sure the tubing is well insulated. Thicker tubing is usually better insulated than thin tubing. Listen with the earpieces in place and binaurals correctly angled while you rub the tubing near the chest piece between your thumb and forefinger. If the noise you hear is loud enough to interfere with the physiologic sounds you want to hear, you know the tubing isn't well insulated.
* The stethoscope head may be a combination diaphragm and bell that can be turned over, depending on which side you need. Your stethoscope may come with extra bells and diaphragms in various sizes, including pediatric, that can be attached to the tubing depending on your needs.
Both bells and diaphragms are available with vinyl coating around the rims to keep chilly metal parts from touching patients.
Some stethoscopes, such as the Littmann models from 3M, use a single-sided head (called a tunable head) that you can switch from bell to diaphragm mode without removing the stethoscope from the patient. You switch modes by pressing the head lightly for hearing low-frequency sounds (such as some murmurs and third and fourth heart sounds) and pressing more firmly for hearing high-frequency sounds (breath sounds; first and second heart sounds).
Which stethoscope is acoustically right for you? Sandra Torres, an ED physician at North Shore University Hospital in Manhasset, N.Y., says that in some situations, differentiating a grade 5 murmur from a grade 6 murmur may not be important, but you should be able to hear that a murmur exists, determine where you hear it best, and identify where in the heart sound cycle it occurs.
Having an acoustic rating scale of various brands of stethoscopes would be helpful, but representatives from organizations that test such medical equipment, such as the ECRI Institute, say a rating scale isn't yet available. One company (3M Littmann) developed a comparison chart of its own equipment, including an overall performance rating of several models of its acoustic and electronic stethoscopes. You could compare the highest-rated 3M stethoscope that you can afford with various other stethoscopes and various ear tip combinations. Or you could try various stethoscope and ear tip combinations at trade shows and stores that sell medical equipment.
Major manufacturers and suppliers of acoustic stethoscopes include American Diagnostic Corp., W.A. Baum Co., Doctors Research Group, Graham-Field Health Products, Heine, MDF Sprague Rappaport, Prestige Medical, 3M Littmann, and Welch Allyn (includes Harvey and Tycos). Prices range from $10 to $200.
Electronic stethoscopes: Pros and cons
A major advantage of electronic stethoscopes is that they can increase volume 10 or more times compared with acoustic stethoscopes. Although electronic stethoscopes are ideal for clinicians with hearing problems, they could damage your hearing by directing unexpectedly loud noises into your ears. For example, if you have the stethoscope set at high volume and a child screams while you're auscultating her thorax, that sound could be amplified to a dangerous decibel level, according to ECRI Institute researcher Ken Ross. Some manufacturers have dealt with this problem by including a feature that automatically mutes loud noises.
Electronic stethoscopes are battery operated, and most have a warning system to let you know when battery power is running low. Some have a small digital display to show battery status, heart rate, and volume level. Some even have ports or infrared devices to let you connect to another electronic stethoscope, computer, or personal digital assistant. This way, more than one person can listen at the same time. Or you can save files of a patient's heart sounds to compare with future results or to use for teaching.
Some electronic stethoscopes have traditional bell and diaphragm modes for use as an acoustic instrument. If the battery fails unexpectedly, the unit can be switched to the bell or diaphragm to hear sounds in traditional nonamplified modes.
Major manufacturers and suppliers of electronic stethoscopes include American Diagnostic Corp., Cardionics, Doctors Research Group, Graham-Field Health Products, 3M Littmann, Thinklabs, and Welch Allyn. Prices range from $200 to $400.
Equipment for special situations
You can use disposable stethoscopes and disposable diaphragms for traditional stethoscopes when you know a stethoscope is likely to become dangerously contaminated (for example, if your patient has open lesions that might be communicable, such as herpes zoster). Some disposable stethoscopes are available for as little as $3.
Stethoscope holders that clip to your waistband give you an alternative to wearing the stethoscope around your neck. And, yes, these holders also come in various colors. Because skin oils can ruin stethoscope tubing, a holder is a good option. (Or you can wear your stethoscope under your collar if you want it around your neck.)
Name tags that can be fastened to stethoscope tubing are available in colors, and some can be engraved.
The best way to clean a stethoscope—ear tips and all—is to wipe it down with one or more alcohol pads. Avoid alcohol gels because many contain lotions that can cause sediment to build up.
What's new, what's next
According to a product manager at 3M Littmann, you can expect to see more new colors and continually improving acoustic technology. Many nurses are hoping that the new technology will include electronic stethoscopes that are as lightweight and as easy to use as acoustic stethoscopes.
Other new equipment you're likely to be seeing soon includes a portable handheld echo device meant to replace Doppler stethoscopes. It will allow you to see as well as hear clinical data.
© 2007 Lippincott Williams & Wilkins, Inc.