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Figure 1: The Bowles stethoscope, patented
in 1901, gave physicians improved amplification of
higher frequency sounds. Photo courtesy of the Wood
Library-Museum of Anesthesiology
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During the first years following a demonstration in 1846 by dentist
W.T.G. Morton, monitoring of anesthetized patients received little
attention beyond the patient's state of consciousness and responses
to surgically induced pain. In Great Britain, an early report
suggesting clinical monitoring is noted in the 1848 legal proceedings
regarding the first death attributed to anesthesia.1
At the coroner's inquest, the anaesthetist, Thomas N. Meggison,
M.D., described his observations of the young victim's respirations,
pulse and the rigidity that occurred just prior to her demise.
In 1847, John Snow, M.D., declared that "the point requiring
most skill in the administration of the vapor of ether is, undoubtedly,
to determine when it has been carried far enough."2
Nevertheless, the means to determine that point would remain illusive
for some time to come.
Joseph Lister, M.D., the founder of the principles of antisepsis
in surgery, was an eminent surgeon in Scotland and the United
Kingdom of the 1850s through the 1890s. He protested against palpation
of the pulse as "a most serious mistake. As a general rule,
the safety of the patient will be most promoted by disregarding
it altogether, so that the attention may be devoted exclusively
to the breathing."3 Dr. Lister's
instruction to the senior students who served as his anaesthetists
was "that they strictly carry out certain simple instructions,
among which is that of never touching the pulse, in order that
their attention may not be distracted from the respiration."
He repeatedly emphasized the importance of airway management,
urged "the drawing out of the tongue" and expressed
the belief that the services of special anaesthetists were unnecessary
if simple routines were followed in the administration of chloroform.
Dr. Lister gave short shrift to monitoring beyond observation
of the adequacy of respiration and whether or not patients responded
to surgical stimulation.
Laünnec Stethoscope
Auscultation of the heart and lungs gained importance following
the description by Réné Théophile Hyacinthe
Laünnec, M.D., of the clarity of cardiac sounds in 1816 when
he rolled "a quire of paper into a sort of cylinder"
and applied one end to his patient's chest and the other to his
ear.4 From this beginning, he constructed
a wooden stethoscope 20 cm (7.87 inches) in length with a hollow
passage through the center and shallow concavities at both thoracic
and auricular ends. He initially called his invention "Le
Cylindre," but later coined the term stethoscope, taking
the name from the Greek words stetho, meaning "chest,"
and scope, meaning, "I see." (A well-preserved wooden
Laünnec stethoscope can be examined in the Wood Library-Museum
of Anesthesiology; see photo on page 8.) The new device underwent
many modifications from the original wooden tube, from flexible
monaural devices, then to binaural stethoscopes with a bell-shaped
appendage on the thoracic end. Flexible rubber tubing connected
the bell to the earpieces. A flexible diaphragm was added to the
thoracic bell and added improved transmission of heart and breath
sounds.
Stethoscopes were not mentioned in descriptions of clinical anesthesia
during the 50 years following Dr. Morton's demonstration, although
they undoubtedly were used to determine the presence or absence
of cardiac sounds in patients who were in distress or were presumed
to be dead.
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Figure 2: The patent for "Dr.
Kehler's Improved Stethoscope" was granted in
1901. Photo courtesy of the Wood Library-Museum of
Anesthesiology
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Bowles Stethoscope
In 1897, Robert C.M. Bowles, M.D., applied to the U.S. Patent
Office with his plans to create a flat chest piece with a shallow
concave chamber covered by a flexible diaphragm like that of a
telephone. This stethoscope offered improved amplification of
higher frequency sounds and was even used to auscult the chest
without requiring patients to disrobe. The patent was granted
in 1901. The flat metal thoracic piece had a tube curved to 90
degrees that was connected to flexible rubber tubing leading to
the ear pieces. The "Bowles" was 51 mm (2 inches) in
diameter and presented a flat silhouette with the connecting tube
extending vertically only 16 mm (0.64 inches) above the upper
surface [Figure 1]. It was manufactured by
G. P. Pilling & Son, in Philadelphia, Pennsylvania.
The Bowles was used by Harvey Cushing, M.D., to auscult respirations
in his experimental laboratory, but the 2-inch diaphragm was adjudged
to be unwieldy during surgery and was removed when the animals'
chests were opened. This stethoscope was then used to determine
blood pressures by detecting Korotkoff's sounds just distal to
the Riva-Rocci cuff placed on the upper arm of patients.5
The Bowles also could be placed on the precordium to detect changes
in cardiac rhythm as well as the intensity of heart beats and
thus offered a means to monitor patients during anesthesia and
surgery. Because of the anesthetists' need to communicate with
(and hear) the surgeon, this application was accepted reluctantly.
Nevertheless, the inconvenience of disengaging one hand to palpate
the pulse was now overcome. During this era, Dr. Cushing urged
anesthetists to observe cardiac and respiratory rates every five
minutes during an anesthetic.5
Kehler Stethoscope
Charles K. Teter, D.D.S., described the benefits of using "Dr.
Kehler's Improved Stethoscope" during anesthesia, especially
in poor risk patients.6 He praised
the convenience of the flat Kehler stethoscope, which "will
usually stay without being held" on the precordium. When
necessary, adhesive tape prevented its being dislodged. The Kehler
stethoscope also was submitted for patent during 1897 and approved
in 1901. The concavity of the chest piece was covered by a firm
diaphragm and presented a low silhouette, identical to the Bowles
[Figure 2]. It was manufactured by Becton,
Dickinson and Company of Rutherford, New Jersey. An advantage
of the Kehler stethoscope was the mobile swivel that enabled one
to turn the tubings within a 180-degree range to auscult the chest.
This feature was probably of little advantage to anesthetists
whose position adjacent to the patient was usually fixed once
the anesthetic and operative procedure started.
Dr. Teter praised the stethoscope because "uninterrupted
information will be given to any and all change[s] in the heart
beat and respiration." He expressed his feeling of confidence
when "every variation of heart sound is at once discernable,
and what might be serious complications can be averted by the
premonitory symptoms thus made manifest."6
(The author certainly agrees and used his Bowles stethoscope during
anesthesia of pediatric patients to auscult the precordium during
residency training in 1953 and for four decades thereafter.)
Author's note: The Bowles stethoscope and the Kehler's
Improved Stethoscope are displayed in the Wood Library-Museum
of Anesthesiology in Park Ridge, Illinois.
References:
1. Knight PR, Bacon DR. An unexplained death:
Hannah Greener and chloroform. Anesthesiology. 2002; 96:1250-1253.
2. Snow J. On the inhalation of the vapor of ether
in surgical operations. London: John Churchill. 1847. In: Bendixin
HK. Forward: The tasks of the anesthesiologist. In: Saidman LJ,
Smith NT. Monitoring in Anesthesia. 2nd Ed. Boston: Butterworth
Publishers. 1984:xi.
3. Duncum B. The Development of Inhalation Anaesthesia:
Part 9: The beginnings of modern anaesthesia. Chapter 18:The jubilee
of anaesthesia. Geoffrey Cumberlege, London: Oxford University
Press. 1947:537-540.
4. Bause GS. An historical backdrop to cardiovascular
monitoring. In: Barash PG, ed. Anesthesiology Clinics of North
America: Cardiac Monitoring. Philadelphia: WB Sauders Co. 1988;
(6)4:666.
5. Cushing HW. Some principles of cerebral surgery.
JAMA. 1909; 52:184-192.
6. Teter CK. Thirteen thousand administrations
of nitrous oxid with oxygen as an anesthetic. JAMA. 1909; 53:448-454.
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James
C. Erickson III, M.D., is Professor Emeritus of Anesthesiology,
Northwestern University, Chicago, Illinois, and is a volunteer
consultant at the Wood Library-Museum of Anesthesiology. |
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