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Macintosh Laryngoscope

 

 

This section is contributed by Ernst Zadrobilek and will be regularly updated to take account of comments on this version.

 

Last updated: March 10, 2005.

 

 

In 1943, Robert (later Sir Robert) Reynolds Macintosh (clinical professor of anesthesia, Nuffield Department of Anaesthetics, University of Oxford, Oxford, England) communicated an entirely new curved blade (incorporating a high vertical flange and a reversed horizontal flange facing to the left) for direct laryngoscopy. Within less than one page of this issue of The Lancet, he descibed the blade and the novel technique of laryngoscopy. This laryngoscope blade was specifically designed for indirect elevation of the epiglottis. 

 

The Macintosh laryngoscope was fashioned after a Boyle-Davis mouth gag. During a tonsillectomy in 1941, Macintosh was impressed by the way this mouth gag (a size larger than intended was used and obviously placed in the vallecula) indirectly elevated the epiglottis and exposed the laryngeal aperture. Richard Salt (senior chief technician of the department) soldered a Davis blade on a laryngoscope handle to make the first prototype. Macintosh experimented with a wide range of blade curvatures in developing the final version for clinical practice.

 

Macintosh noted at the end of his first published description of the new laryngoscope blade, that it can be obtained from Medical Industrial Equipment Limited (London, England). The commercial production was soon taken up by others as well. In a letter to the journal one year later (Lancet 1:485:1944), he refers to the Longworth Scientific Instrument Company Limited (Abington, England) as commercial producer. In 1943, three technicians from the Oxford university laboratories formed this company as a spare time venture. They later moved from Oxford to larger premises in Abbington; the company has grown to become Penlon Limited at the same location.

 

The Foregger Company (New York City, New York) also started the commercial production of the new laryngoscope blade in 1943. Macintosh gave one of the early models of his new instrument (handmade by Salt) to Richard Foregger (the son of the founder of the Foregger Company, at this time anesthetist in the army of the United States) to ensure it was sent to North America safely. Unknown to Macintosh, although quoting him as inventor, the Foregger Company immediately applied  for a United States patent claiming novelity for the entire form of the blade. This was granted for the North American market the following year mistakenly under the name MacIntosh instead of Macintosh; Macintosh refused any remuneration for the patent.

 

The catalog of the Foregger Company edited in 1949 announced this laryngoscope blade as MacIntosh Laryngoscope, the original design of Professor MacIntosh of Oxford University. The blade block had a hook-on mechanism for attachment on the battery handle, either with a posterior spring clip (for fastening the blade in its working position) or the still familiar means of attachment with spring-loaded ball catches, developed and patented by the Welch Alleyn Company (Skaneateles, New York). Recently edited catalogs of various manufacturers and even current textbooks still name this instrument MacIntosh laryngoscope. Beyond that, the spelling McIntosh laryngoscope may also be found in catalogs of manufacturers. 

 

The Macintosh laryngoscope blade was intially manufactured in one size for adult patients (corresponding to the current blade size 3). Later, at the request of anesthetists who encountered difficulties with the standard size in large adult patients, an elonged blade was added. Sizes for use in pediatric patients and infants were also manufactured, but Macintosh condemned them as anatomically wrong and generally unnecessary. There were infinitely better commercially available pediatric and infant designs such as the Seward laryngoscope with a reversed flange, the Oxford infant laryngoscope of Bryce-Smith, or later, the laryngoscope developed by Robertshaw. 

 

The curve of the blade in the original design had a slight but distinct flattening of the midportion. With the manufacture of blades made of stainless steel, this flattening disapeared in many models and the blade assumed an entire curved shape; frequently, the vertical flange did not end abruptly away from the tip of the blade (as in the original design), but continued close to the tip. Likewise due to manufacturing considerations, the original stepped swan-neck form of lateral edge of the reversed flange was eliminated and it took a continuous smooth line to the tip of the blade.

 

Various manufacturers produced versions with removable light carriers for easier cleaning and disinfection without running the risk of damaging the electrical system; such a system was communicated by Ritchie for the product line of Medical and Industrial Equipment Limited. Later, fiberoptic light carriers were introduced; fiberoptic light bundles incorporated in the blade are now the standard in the production of any laryngoscope blade.

 

It is nearly impossible to enumarate and describe all the modifications of the Macintosh laryngoscope which have been developed and communicated. There were blades with additional length and lessened curvature, blades with increased angles of the blade block with the handle, flange-reduced and even flangeless blades, blades with malleable distal end, blades with the vertical flange at the right side and a reversed flange facing to the right, and blades with a levering tip or flexible and adjustable intermediate portion. 

 

 

Macintosh Laryngoscope (Medical and Industrial Equipment Limited, Object Number 1)

Macintosh Laryngoscope (Penlon Limited, Object Number 2)

Macintosh Laryngoscope (Instrument Maker Carl Reiner, Object Number 3)

 

Macintosh Laryngoscope (Ritchie Modification, Medical and Industrial Equipment Limited)

 

 

References:

 

Foregger R. Richard von Foregger, Ph.D., 1872-1960. Manufacturer of anesthesia equipment. Anesthesiology 84:190-200, 1996.

Jephcott A. The Macintosh laryngoscope. A historical note on its clinical and commercial development. Anaesthesia 39:474-479, 1984. 

Macintosh RR. A new laryngoscope. Lancet 1:205, 1943.

Macintosh RR. Laryngoscope blades. Lancet 1:485, 1944.

Macintosh RR. Richard Salt of Oxford, anaesthetic technician exrtraordinary. Anaesthesia 31:855-857, 1970.

Ritchie JR. Modified Macintosh laryngoscope. Anaesthesia 11:344-345, 1956.

The Foregger Company Catalog Number 9. New York, p 106, 1949.


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