In 1963, Harvard Medical School Professor David Littmann, a renowned cardiologist, invented a stethoscope which would revolutionize the world of medical auscultation. Stethoscope design had changed little since the nineteenth century but Littmann realised that the requirements for listening to low and high pitch sounds were different. Accordingly he patented his dual sided stethoscope which incorporated a chest piece with an open side for listening to low pitch sounds and a closed side which filtered out lower pitched sounds. In addition, the Littmann stethoscope incorporated features which made it comfortable for the practitioner to use as well as light and practical to carry. The level of sound produced by the new design made such a profound improvement on what had gone before that in 1967 the 3M corporation acquired Dr Littmann’s company, Cardiosonics Inc.
As a world leader in health care products 3M continued to improve and develop the Littmann stethoscope and and in 1978 worked very closely with leading figures in the medical profession to produce the 3M Littmann Cardiology Stethoscope. This became known as the “cardiologists dream stethoscope” and featured a dual tube and an enhanced low frequency sound capability.
In 1987 a major product development breakthrough was made by 3M engineers who introduced tunable diaphragm technology to the Littmann stethoscope. Although Littmann had produced a stethoscope which was ground breaking at the time it was not without its drawbacks – the main of which involved having to remove the chest piece from the patient in order to listen to different types of sound. The new tunable diaphragm technology allowed the practitioner to alter the pressure on the chest piece in order to change from bell mode to diaphragm mode and vice-versa. Accordingly the chest piece does not need to be moved in order to be optimized for different sound frequencies. This represented a hugely significant breakthrough in the area of auscultation and in addition the fact that low frequency sounds were being amplified by a diaphragm rather than a bell meant that amplification was much greater and much clearer.
More recently 3M has developed electronic Littmann stethoscopes which contain microphone and low noise amplification allowing chest sounds to be heard 18 times louder than with conventional equipment. These state of the art stethoscopes also allow sounds to be recorded and transferred to a PC in order to be analyzed. Littmann stethoscopes continue to be the market leader in today’s technologically advanced health care market. There can be no doubt that Dr Littmann would approve of the legacy he created.
3M Littmann Stethoscopes
Littmann Select Stethoscope – basic model for general examinations
Littmann Lightweight Stethoscope – suitable for nurses
Littmann Classic II Paediatric and Infant Stethoscope – Specialist Paediatric model
Littmann Classic II Stethoscope – the standard Littmann bell design allied to a tunable diaphragm
Littmann Master Stethoscope – single sided technology
Littmann Cardiology III – features 2 tunable diaphragms
Littmann Electronic E2000 – up to 14 times the amplification
Littmann Electronic E4000 – up to 18 times the amplification with recording software
3M and Littmann are registered trademarks of the 3M Corporation
Daniel Morris is a writer and owner of the web site
www.littmann-stethoscopes-online.com