The 'Keeler Polygraph' Model 6338 shown here was the first 'Plethysmic Polygraph' manufactured by 'Associated Research' of Chicago, Illinois in the early 1950's. This instrument is the first in the 'Pacesetter Series' which incorporated for the first time a integral photo/optical plethysmograph. The Model 6338 was introduced as a four channel instrument, which recorded simultaneously changes in relative blood pressure, heart rate, pulse wave amplitude, blood volume, oxygenation of the blood, respiration and electrical skin resistance. These reading are obtained by utilizing electronic and pneumatic monitoring.

The 6338 required a 115 volt AC current. It weighs twenty-four pounds and is 18" x 11" x 6". The 6338 incorporated newly designed printed circuits, and a new inking system where the pens are fed from removable, individually capped ink bottles with colored ink available. The newly designed vent valves have a positive lock to prevent leaks.

The kymograph is typical of previous top loading models, but the construction allows the instrument to be mounted in a desk top. The new shockproof suspension system protects the instrument as it is suspended between two layers of foam rubber. The design of the cardio cuff, pump bulb assembly and clamp remained basically the same in the 'Pacesetter Series'. There were three different traveling cases available, which conformed to Federal Aviation requirements at the time for travel. The price for this model was $2325.00. The 'Keeler Polygraph' Model 6338 remained in service through the early 1960's.

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