The State of the Stethoscope


 
 

Howard Rodenberg, MD, MPH, Dip(FM) | | Tuesday, November 27, 2007


Loyal readers of this column will be familiar with my theory of the cheap stethoscope, which postulates that anything you can actually hear through a device with such poor acoustics must really be there. Truth be told, I also own a fine stethoscope. It s one of those $150 models you buy in school, with double tubing, a magnificent weighted chrome chest piece, a bevy of bells and diaphragms, and lined in rich Corinthian leather.

The problem is that it came with short tubing. In medical school, where the physical diagnosis course is taught by internists, nobody ever tells you that there are occasions where you might not want to get too close to the patient. You can t blame them for this view; internists tend to see patients after their bleeding, kicking, grabbing and spitting is controlled by the judicious use of chemicals. That s why throughout my career I ve used a more "enlightened" model cheap, disposable, with a healthy two feet of tubing to give me adequate distance from whatever might come my way. (I suppose one might argue that I accept an added risk of strangulation with longer tubes, but the presence of many large angry bodies dressed in blue security uniforms often seems to mitigate that threat.) This is why my wonderful, expensive, sentimental medical school stethoscope lies in a bedroom drawer.

However, last week I was confronted with the new and novel challenge of the nonfunctional stethoscope. Suddenly patients who should have had breath sounds any breath sounds had none. Because their O2 sat was still 93% on room air, I thought this was bad.

When I did quality assurance work, I tried to remember that most often individuals don t fail, but the system does. So the stethoscope was clearly the root of the problem. It couldn t be my fault for not listening properly. And as a non-transient with a fixed abode and a regular user of soap and water about the head and face, I was pretty confident that wax, dirt or other foreign objects (as opposed to domestic objects, which are made in America) were not stuck in my ears.

Being a technical wizard (see my column on how I wrestled with, and lost to, a PDA stylus) and a full-blooded chromosomal male, my first instinct was to tear the stethoscope apart. The earpieces came off easily, and I cleaned them out with a cotton swab. (The swabs were pure as both the driven snow and my mother s virtue.) I removed the plastic hoses from the metal pipes and peered into the passages. I took off the diaphragm and cleaned it with an alcohol wipe (amazing how much stuff gets between the plastic and the rim) and then dismantled the head of the stethoscope. The head wouldn t turn back and forth between the diaphragm and bell sides (I was supposed to use both sides?), so I twisted the joint with a pair of pliers and sprayed the whole thing with WD-40. (I have great faith in the ability of WD-40 for fixing anything sort of like liquid duct tape.) However, my best efforts to break, mangle and damage the device netted no change in the stethoscope s ability to transmit subtle and insignificant findings like breathing and heartbeats. Clearly, it was time to actually learn something about the history, care and feeding of stethoscopes.

The stethoscope was invented in 1816 by Rene Theophile Hyacinthe Laennec, a tubercular young man who probably had no great desire to place his ear on the patient s torso to hear the heartbeat (the fashion of the time). Nor, I suspect, did people particularly want him coughing up bacilli next to their chests. But I ll let him tell the story:

"I was consulted in 1816 by a young woman who presented some general symptoms of a disease of the heart, in whose case the application of the hand and percussion gave but slight indications, on account of her corpulency. On account of the age and sex of the patient, the common modes of exploration being inapplicable, I was led to recollect a well-known acoustic phenomena, namely, if the ear is applied to one extremity of a beam, a person can, very distinctly, hear the scratching of a pin at the other end. I imagined this property of bodies might be made use of in the present case. I took a quire of paper which I rolled together as closely as possible and applied one end to the precordial region; by placing my ear at the other end, I was agreeably surprised at hearing the pulsation of the heart much more clearly and distinctly than I had ever been able to do by the immediate application of the ear."

(As an aside, I have great regard for this kind of writing. It is rich, eloquent, picturesque and clearly intended for posterity in an era where the written word was the only tangible memory one could give. It reminds me of the thoughts of one Mr. Humphrey W.S. Piggott, a surgeon at the West Suffolk Hospital in Bury St. Edmunds, England. He considered the invention of the ballpoint pen to be the downfall of modern society, for it made written communication cheap, disposable and thoughtless. Amen to that.)

The first stethoscope was a rolled up sheaf of paper; advanced models were cylinders of wood with a hole bored through the middle (our mod, swingin hep-cat binaural device, with a separate tube leading to each ear, was developed by G.P. Cammann in the early 20th Century). Nonetheless, Krumbhaar notes in his "A History of Medicine," that with the stethoscope, Laennec was able to describe bronchial breathing, vesicular and cavernous respiration, metallic tinkles and a constellation of crepitant, mucous, bubbling and sonorous rales, which is a lot more than I ve ever heard. Then again, Laennec died of consumption in 1826, so perhaps he packed a lot of extra listening in 10 years.

For more information on the delights of the stethoscope, I turn to Joseph Sapira ("The Art and Science of Bedside Diagnosis") for a discussion of the length of the tubing. Noting that shorter tubing has been demonstrated to provide better sound volumes, he advises that when the tubing is less than 12 inches long, what one loses in comfort and the ability to concentrate (especially if one is examining California Gubernatorial Candidate Mary Carey or Ah-nold Schwarzenegger, depending on your sensitivities) offsets the gain in proximity. Sapira also makes note of stethoscopes with very long tubing, sometimes up to three feet in length, from the time when one did not wish to get too close to a patient with tuberculosis. Sound advice for today as well.

Here is how he says you can figure out which stethoscope is best for you. "Place an earpiece of one stethoscope in your left ear and an earpiece of the second stethoscope in your right ear. Place the diaphragms of both stethoscopes in front of you, equidistant from a point two to three feet away on a solid surface. Tap on the point, and, in the manner of someone adjusting stereo speakers, notice whether the sound is louder in one ear than the other. To control for the possibility that your hearing is better in one ear, switch the earpieces and repeat the experiment. ... If you have an extra pair of hands, you might want to try this experiment with the unattached earpiece of each stethoscope occluded by a finger."

(Personally, I like the vision of stethoscope selection as a team effort. Round up three of your closest buddies, lay in a few six-packs, and go shopping. You hold the earpieces in you ear; a second guy holds the diaphragms on the table; a third guy hits the table; and the fourth puts his fingers over the earpieces not in your ears. I see whole family outings coming from this process.)

The Littmann Company Web site offers a host of data regarding the treatment of your stethoscope. You ve seen this information before; it s in the little folded package of paper that comes with your new auscultatory toy that you promptly dispose of in the "circular file." But it does contain some useful precepts. One is that you should never immerse your stethoscope in any liquid. This means that when I would get stuff on the stethoscope that I didn t want breeding in my pocket, and I would decide that the best way to clean it was to fill an unused bedpan with hydrogen peroxide and toss the stethoscope in it, it was a bad idea. A second concept is that you should not wear the plastic tubing of the stethoscope around your neck. It turns out that the polyvinyl chlorides comprising the tubes become stiff on prolonged contact with the lipids in human skin. This was verified when one of my colleagues removed his long-toiling stethoscope from around his neck to find that it was especially stiff and attentive to duty, ready and eager to assume its role in patient care (no aural Viagra needed here).

Sapira offers one more disturbing tidbit about stethoscope care. Besides the routine admonitions to clean the earpieces with alcohol, he suggests the use of a pipe cleaner to clear out parts of the stethoscope that extend beyond the earpieces. He notes, "Persons who produce copious quantities of ear wax have, on occasion, noted it to be appearing at the chest pieces."

Let s get a mental picture of this interesting, if somewhat distasteful, event. There is a collection of earwax that has migrated over the years into the tubing of the stethoscope. Like a paraffin cockroach, it cannot be seen, yet lurks just inside the metal pipes and polyvinyl tubes. The only way to identify its presence is to take a long pipe cleaner and insert it into the tubing. What should emerge is a long, 18-inch, snake-like plug of cerumen, the oldest portion of which is a decade old (it s sort of like taking a core sample from the artic to look for evidence of climate change, but a whole lot weirder). Even for me, this was too strange a thought to contemplate, let alone to go the local smoke shop and ask for a two-foot pipe cleaner, which would probably require an explanation. If my stethoscope was plugged with auditory debris, so be it. I just wasn t going there.

So now I have a new stethoscope. I found an ideal candidate, an $8.99 model in a public safety catalogue, resplendent in a Henry Ford-like basic black. ("They can have whatever color Model T they want, as long as it s black."). But this was not for me. As a physician devoted to quality care and as a member of the elite team of physicians caring for patients in Florida s third-busiest ED, I decided to upgrade. I now sport one that costs $13.99, resplendent in dark blue to match my car, just out of the box and presumably wax-free. I can hear a lot better now. But fortunately, I still don t hear anything I can t identify.


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