Valve, Armstrong-Mohler, 1969, Diagram

From Journal of Applied Physiology, 1969 27(5): page 765.

“O2 deficit and debt.  A collection bag is connect to each outlet (A, B, C, D).  Initially when the valve is in the position shown, exhaled gas flows from the mouthpiece and into the bag on the outlet which is in position A.  When this collection period ends the outer rim is rotated so that outlet A is in position B, and an empty bag is in position A. When the next collection period begins a third empty bag is in position A, the second collection bag is in position B and the first bag is in position C and ready for sampling. When the fourth collection period begins the above sequence is repeated, and the first bag is rotated into position D and emptied into the Tissot. The first bag is ready to be refilled when turned to position A at the beginning of the 5th gas collection.

Spirometer, Collins, modified by Gaensler for Timed Vital Capacity, 1951

From ‘Analysis of the ventilatory defect by timed vital capacity measurements.’ By Edward Gaensler, American Review of Tuberculosis, 1951; 64(3): page 260.

“Fig. 1. Vital capacity spirometer with timed capacity attachment and electronic timer.  The insert shows the timing device with the cover removed.  On the left is the micro-switch which initiates the timed interval when the spirometer bell begins to rise.  On the right is the midget solenoid  which moves the added second pointer only while it is activated by the timer. “

The diverse, quirky and mostly forgotten history of Pulmonary Function testing