Monthly Archives: April 2014

1910s, Diagram, Spirometer

Spirometer, Rebreathing system for altitude simulation, 1918, diagram

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Spirometer_Rebreathing_System_Altitude_Simulation_1918_Diagram

From: Manual of Medical Research Laboratory, United States School of Aviation Medicine, Randolph Field, Tex, United States. War Dept. Division of Military Aeronautics, U.S. Government Printing Office, 1918, page 214.

“The base of the machine is a steel tank (T) of 60 or 80 liters capacity, according to the type.  Type A has 80-liter, and types B and C 60-liter tanks. Air is inspired from the tank through the pipe at the left, and is expired back into the tank through the pipe and absorbing cartridge (A) at the right. The valves (VV) keep the air stream flowing always in the proper direction.  In order to maintain the contained air at approximately atmospheric pressure and to allow for changes in volume, a wet spirometer (S), carefully counterbalanced, is mounted on the tank and communicated freely with its interior through the vertical pipe (P). A stylus attached to the counterweight records the movements of the spirometer upon the smoked drum of the kymograph (K).  Water is admitted to the tank through valve (E) to replace the volume of the used oxygen and also to flush out the tank after an experiment. The water is drained away to the sewer by means of valve (F).  Valve (C) affords a free opening to the atmosphere for flushing the tank of the rebreathed air.  Valve (D) should invariably be closed while flushing the tank, otherwise wate will enter the absorption chamber (A) and ruin the cartridge.  The cartridge is a cylindrical paper tube filled with solid caustic soda, cast in thin shells so as to expose a large surface to the action of the gas.  IT is prepared for use in the machine by punching the ends full of quarter inch holes with a pencil.  The brass ring is then inserted in the lower end of the cartridge, the rubber ring fitted over the end, and the whole inserted into the absorption chamber.  Cartridges should never be used without both rubber ring and brass ring in proper position. Valve parts may be removed from the air valves (VV) by means of the brass spanner wrench, which, together with two new valve parts are furnished with each machine.  Counterweight slide rods should be frequently greased with vaseline and the pulleys oiled.  In setting up a machine care should be taken to level it properly, so the the inner can of the spirometer hands freely in the outer can and does not rub against the side.”

1960s, Drawing, Spirometer

Spirometer, Med-Science Wedge Spirometer, 1964

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Spirometer_Med-Science_Wedge_1961_Patent_Drawings

A drawing from patent #3,154,068, submitted 1961, approved 1964.

“Another object of the invention is to provide a high dynamics spirometer. The instrument is designed to have small travel of the parts in motion corresponding to large volume differentials or changes in volume. Therefore large volumetric acceleration with correspond to small linear acceleration. Since for a given mass in motion, the lower the accelerations, the higher will be the frequency response.

“Another object of the invention is to provide a spirometer which will offer all the known functions of previous spirometers, and at the same time provide an electrical readout of both volume change and flow changes. These two measurements are entirely independent. Previous to this invention, no patient-driven spirometer has been capable of independent readout of volume changes and flow changes.

“The low linear acceleration results in small forces required to actuate the moving elements. Since the patient’s lungs in mechanical spirometry are required to generate the forces to drive the spirometer, it can readily be seen that the lower linear accelerations result in lower forces in the lungs to drive the spirometer. Thus the patient’s breathing is more nearly normal during the process of measurement. The effect is magnified at the point of higher dynamics, such as rapid breathing and coughing.

“In an ordinary spirometer, a patient coughing is not only affected physiologically by the higher forces of the ordinary spirometer, but the actual cough is recorded subject to the errors of the instrument at high frequencies.

“A further object of this invention is to provide a spirometer in which the ambient pressures within the spirometer and the patient’s lungs remain as close to atmospheric pressure as possible. Thus the patient does not have the feeling that something is impeding his breath, which is the case in the ordinary spirometer.”