Thursday, 10 February 2011

How far can a Flea Jump. Should a Medical Doctor Know the answer?

Fleas can jump two hundred times the length of their own bodies, which is roughly about thirteen inches. If a grown man could jump 200 times the length of their own bodies, they could jump about 900 feet!
Thirteen inches works out to be about 33 cm. let us say 35 cm.
Why is a doctor interested in this spectacular feat of a Flea?
Go back a few years, this medical student from Australia assigned to the Cardiology team at Brompton Hospital in London, listening carefully to the Consultant Cardiologist. Among the many things, he learned, was that one has to be able to guess correctly within a point the Hemoglobin level, i.e. whether the patient is anemic or not. The secondly, one of the conferences at the hospital, famous for its wit, forced subdued nature and erudite professors hard of hearing (Dr Simon, the radiologist was a show in himself!), I listened an argument for the ideal length for the tubing of a Stethoscope.

Early stethoscopes.

The stethoscope was invented in France in 1816 by René Laennec at the Necker-Enfants Malades Hospital in Paris. It consisted of a wooden tube and was monaural. His device was similar to the common ear trumpet, a historical form of hearing aid; indeed, his invention was almost indistinguishable in structure and function from the trumpet, which was commonly called a "microphone". In 1851, Arthur Leared invented a binaural stethoscope, and in 1852 George Cammann perfected the design of the instrument for commercial production, which has become the standard ever since. Cammann also authored a major treatise on diagnosis by auscultation, which the refined binaural stethoscope made possible. By 1873, there were descriptions of a differential stethoscope that could connect to slightly different locations to create a slight stereo effect, though this did not become a standard tool in clinical practice.

Rappaport and Sprague designed a new stethoscope in the 1940s, which became the standard by which other stethoscopes are measured, consisting of two sides, one of which is used for the respiratory system, the other is used for the cardiovascular system. The Rappaport-Sprague was later made by Hewlett-Packard. HP's medical products division was spun off as part of Agilent Technologies, Inc., where it became Agilent Healthcare. Agilent Healthcare was purchased by Philips which became Philips Medical Systems, before the walnut-boxed, $300, original Rappaport-Sprague stethoscope was finally abandoned ca. 2004, along with Philips' brand (manufactured by Andromed, of Montreal, Canada) electronic stethoscope model. The Rappaport-Sprague model stethoscope was heavy and short (18–24 in (46–61 cm)) with an antiquated appearance recognizable by their two large independent latex rubber tubes connecting an exposed-leaf-spring-joined-pair of opposing "f"-shaped chrome-plated brass binaural ear tubes with a dual-head chest piece.

Several other minor refinements were made to stethoscopes, until in the early 1960s Dr. David Littmann, a Harvard Medical School professor, created a new stethoscope that was lighter than previous models and had improved acoustics. In the late 1970s, 3M-Littmann introduced the tunable diaphragm: a very hard (G-10) glass-epoxy resin diaphragm member with an overmolded silicone flexible acoustic surround which permitted increased excursion of the diaphragm member in a "z"-axis with respect to the plane of the sound collecting area. The left shift to a lower resonant frequency increases the volume of some low frequency sounds due to the longer waves propagated by the increased excursion of the hard diaphragm member suspended in the concentric accountic surround. Conversely, restricting excursion of the diaphragm by pressing the stethoscope diaphragm surface firmly against the anatomical area overlying the physiological sounds of interest, the acoustic surround could also be used to dampen excursion of the diaphragm in response to "z"-axis pressure against a concentric fret. This raises the frequency bias by shortening the wavelength to auscultate a higher range of physiological sounds. 3-M Littmann is also credited with a collapsible mold frame for sludge molding a single column bifurcating stethoscope tube with an internal septum dividing the single column stethoscope tube into discrete left and right binaural channels (AKA "cardiology tubing"; including a covered, or internal leaf spring-binaural ear tube connector).

In 1999, Richard Deslauriers patented the first external noise reducing stethoscope, the DRG Puretone. It featured two parallel lumens containing two steel coils which dissipated infiltrating noise as inaudible heat energy. The steel coil "insulation" added .30 lb to each stethoscope. In 2005, DRG's diagnostics division was acquired by TRIMLINE Medical Products.
As you can see from the photograph, I have my own version of the Noise Reduction technology: the ancient form of beading, this one done by a member of the Hocank Tribe of Indians of Nebraska!
(For lovers of History of Medicine, what other Medical phenomena are associated with the illustrious dr Laennec associated with?)
I still treasure the headpiece of my first ever stethoscope, which was a Sprague Rappaport Original. Nowadays you can find Chinese knockouts of the SR model but you can tell their fake origins by the long tubes, much longer than the flight of a flea!

Cambridge University scientists have solved the mystery of how fleas jump so far and so fast.
It was known that the energy to catapult a flea over a distance up to 200 times its body length lay in a spring-like structure in its body.
But scientists did not understand how they transferred this energy to the ground in order to jump.
High-speed footage now reveals that the secret lies in the way fleas use their hind legs as multi-jointed levers.
This "lever-effect" allows fleas to drive their feet onto the ground, and the sudden release of the "coiled spring" hurls the insect forwards and upwards, scientists report in the Journal of Experimental Biology.
Jumping controversy
Half a century ago two groups of researchers first discovered that the energy for the insects' jumping ability was contained in an internal spring, rather than in the fleas' miniature muscles.
Spines on the back of the flea's hind leg grip the ground for "take-off"

Thus the Cambridge University scientists have added to the ontology of our medical knowledge! Thank you… I am grateful.
This piece is dedicated to two future Jewish professionals, whose name in Hebrew mean:
1. Requested of God 2. Delicate