Quite often health care workers raise questions regarding tubing length
based on early publications claiming shorter tubing length provides
better acoustic response. Some instructors have recommended their
students buy the shortest tubing possible. In an attempt to clarify the
information surrounding tubing length, Littmann stethoscopes has tested
their product line to offer the following information about tubing
length.
To explain our test results, it will be helpful to compare the tubing
of the stethoscope to a garden hose. For example, an increase in the
length of a garden hose will decrease the pressure at the end of the
hose as a result of frictional and other internal forces. The same
effect occurs when the tubing length of a stethoscope is increased.
However, in the case of stethoscope tubing, change in length is
relatively small; this decrease in acoustic pressure is not detectable
by the human ear.
Additionally, as tubing length increases, resonant frequency decreases.
Considering this fact, an increase in tubing length provides a better
response to the lower frequency sounds (an advantage in auscultation).
Many heart sounds fall below 150 Hz and are considered low frequency.
Because it has been shown that the human ear is least sensitive to low
frequency sounds, improved low frequency response is an advantage.
Taking these two factors into account, there is no detectable difference
in acoustical performance between Littmann stethoscopes with shorter
tubing vs. those with longer tubing. In fact, there may be some
enhancements to low frequency sounds.
When purchasing a stethoscope, the health care practitioner needs to
consider their own needs and practices. Longer tubing might be more
appropriate for people wearing the stethoscope around their neck
as it drapes better. The practitioner’s height and arm length should
also be a factor to determine optimal tubing length. Many practitioners
would like a little more distance from sicker patients while
auscultating. Longer tubing also reduces the amount needed to bend over
the supine patient which can stress the practitioner’s lower back.
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