Medical folklore—the use of your stethoscope's bell
BMJ 2007; 334 doi: https://doi.org/10.1136/bmj.39098.406852.BE (Published 01 February 2007) Cite this as: BMJ 2007;334:253
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My stethoscope’s bell and discovery of a new Parkinsonian physical
sign (Kaps sign) in Clinical Medicine
I enjoyed reading Michael Reschen’s communication [1] but to
“proclaim the bell should find its rightful place in the history books”
[1], meaning discarding the hollow object is not how I view it. I regard
it as deserving to be in the history books for its usefulness because 40
years ago, I discovered a new physical sign – the Kaps sign – using the
bell of my stethoscope.
When I announced in Ghana my discovery that Parkinsonian tremor was
audible, one Visiting Professor was vocally sceptical: “And how can you
possibly explain that?” A few minutes later, quite astonished, he himself
was guiding fascinated medical students where to place the bell for
maximum audibility: “at the elbow of the shaking arm half way between the
biceps tendon, and the medial epicondyle” [2]. My second patient was a 53-
year old Scottish woman living in Ghana who “had only the suggestion of
facial akinesia. No arm tremors could be seen or heard, but there was
unusually marked tremor of the legs while sitting with the heels off the
floor, in ‘tip-toe’ position [3]. With the bell of the stethoscope one
could count 300 beats per minute (counting 2 beats as one) on the medial
aspect of the left popliteal fossa” [3]
A Cardiopan 573 was used to record sounds from the arm of the first
patient and from the leg of the second – tracings I respectively called
phonobrachiogram and phonocrurogram [2, 3]. This konotey-ahulu
parkinsonian stethoscope (Kaps) sign was elicited near the Achilles tendon
in another patient, the phonocrurogram rate equalling that of a
kinenometer usually used “in recording the Achilles Reflex in thyroid
disease”. [3]
Medical students monitored tremor rate to discern variations with
treatment. In another patient, “one could hear the sounds at the elbow
while the arm looked perfectly still” [2], helping to “pick up
Parkinsonian tremor long before it was visible” [2]. The bell can catch
the sound better over tiny areas, while a diaphragm is awkward over the
posterosuperior aspect of the lateral malleolus where Achilles tendon
contractions are best heard.
Bedside counting of tremor rate may “help one distinguish between
paralysis agitans and post-encephalitic Parkinsonism and thereby allow one
to prognosticate” [3] because, quoting Lord Brain, “The rate of
Parkinsonian tremor lies between 4 and 8 movements a second, being slower
in paralysis agitans than encephalitic Parkinsonism” [4]. As Walshe
recognises a less common form of paralysis agitans “in which tremor is
absent throughout” [5], I concluded that “one expects to see and be able
to hear tremor at one time or other during the course of most cases of
paralysis agitans”. [3] Do not throw away your stethoscope bells yet!
The temptation to do that is great, because “inspection, palpation,
percussion, and auscultation” - the quadrilateral pillars on which British
undergraduate Medicine stood head and shoulders above all comers worldwide
– appear to be in the process of being deprecated in favour of the
exciting new gadgets crowding the frontiers of knowledge. British Medical
Education, in those days, trained one for the bush, literally. O for those
days to come back!
F I D Konotey-Ahulu
Kwegyir Aggrey Distinguished Professor of Human
Genetics, University of Cape Coast, Ghana and Consultant Physician &
Genetic Counsellor, 10 Harley Street, London W1N 1AA.
felix@konotey-
ahulu.com
Competing interests: None declared
1 Reschen M. Medical folklore – the use of your stethoscope’s
bell. BMJ 2007;334: 253. (3 February)
2 Konotey-Ahulu FID. Audible Parkinsonian tremor. Lancet 1968; 1:
732 (April 6).
3 Konotey-Ahulu FID. Use of stethoscope in Parkinsonism – a new
physical sign? Ghana Med J 1967; 6: 131-133.
4 Brain (Lord). Clinical Neurology, 2nd Edition (Oxford University
Press), pp 66 & 223.
5 Walshe, Francis. Diseases of the Nervous System, 10th Edition (E
& S Livingstone Ltd, Edin & Lond), p 222
Competing interests:
None declared
Competing interests: No competing interests
I sat the PACES exam this morning, just 1 working day after this
anecdote was printed. I did not use the bell and the examiners made no
comment.
Littman have been fitting 'non-chill' rims for at least 10 years; I
would consider older models obselete for the reason Dr Cave stated.
Dr Faller reiterates my point regarding the old-fashioned bell by
observing that Littman themselves have made a single sided stethoscope for
many years. Looking around we can see that it has never really caught on;
partly because the bell remains cemented in medical folklore - hence my
article.
Personally, I prefer the double sided stethoscope because the
paediatric diaphragm is useful for cachectic adults, carotids and
children.
Competing interests:
None declared
Competing interests: No competing interests
Oh dear Michael,
You really do need to read the instructions more carefully. It is only the
diaphragm of Littman stethoscopes that can do the clever trick of altering
the frequency sensitivity with pressure, and only their diaphragms with
the rubber like rim. A standard diaphragm cannot do that trick. The other
thing a diaphram cannot do is be warm to the touch and for this reason my
(non-Littman) stethoscope will keep its bell and "nice Dr Cave" will not
make his patients jump out of their skin.
Competing interests:
None declared
Competing interests: No competing interests
I know Mike well, and this filler article shows his typical wit. As
we all know, however, observation skills are the essence of PACES (the
Royal College of Physicians clinical exam), and so I am surprised how long
it has taken Mike to notice that for several years the Master Cardiology
series of Littmann stethoscopes has been available. These stethoscopes
have no bell side at all, but simply have an indentation for ones index
finger. But I would take his advice with a word of caution - patented
technology from some manufacturers for tunable diaphragm technology does
not mean all stethoscopes come so equiped - indeed it may be a feature of
only premium stethoscopes in a manufactures range. Admittedly they are now
much more common, but until the technology is absolutely standard, I
suspect PACES examiners are quite right to continue making sure candidates
are seen to use a bell.
Competing interests:
None declared
Competing interests: No competing interests
The stethoscope bell
I wish to congratulate Dr. Reschen on realising the limitations of
his stethoscope bell (1). I agree the superior properties of the
diaphragm have yet to become commonly accepted. You may be interested to
learn of an elegant study of the audio characteristics of the Littman
Classic II stethoscope (one of the most commonly used). In this paper,
the diaphragm was found to be superior to the bell for transmitting subtle
harmonics (2). These high frequency sounds allow the accurate
characterisation of breath and heart sounds.
The same study reports a wide variety of teaching on the correct
technique for auscultation. A review of 8 commonly used clinical
examination textbooks revealed 2 advocated the bell, 3 the diaphragm, and
3 both (2). The teaching habits of 32 respiratory consultants and
professors across the UK were also surveyed. Seven taught the use of the
bell for auscultating breath sounds, 15 the diaphragm, and 10 both.
It appears the technical performance of stethoscopes bears little
impact on the way medical students are taught to auscultate. In an era of
evidence-based medicine it is perhaps time to start practicing evidence-
based teaching to update clinical practice.
1. Reschen M. Medical folklore – the use of your stethoscope’s bell.
BMJ 2007;334:253
2.Welsby PD, Parry G, Smith D. The stethoscope: some preliminary
investigations. PMJ 2003;79:695-8
Competing interests:
None declared
Competing interests: No competing interests