Category Archives: Diagram

1910s, Diagram, Douglas Bag

Douglas Bag, 1916

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Douglas_Bag_1916

From: The respiratory exchange of animals and man by August Krogh, 1916, page 42.

“Regnard [1879] collected the expired air in a rubber bag from which it was afterwards delivered and measured through a meter, but his bags were probably not tight against diffusion and his technique very faulty.  This principal, however, is excellent for certain types of experiments, and it has recently been revived by Douglas who has worked out a method which is specially adapted for the study of the respiratory exchange during open-air exercise in circumstances where all other instruments would fail, but which also prove useful in a number of other cases, e.g. on bed-ridden patients (Fig. 17). The subject breathes during an introductory period through the mouthpiece and valves.  When it is desired to make an experiment the three-way tap is turned so as to connect with the bag and the expired air collected over a certain period.  With violent exercise a bag taking 60 liters will not hold the air expired during one minute, but is has been shown (Krogh [1913]) that experiments of even shorter duration are sufficient to give perfectly reliable results. The air collected in the bag is afterwards analysed and measured by connecting with a gas meter of suitable size and pressing the air slowly out of the bag. When a gas analysis is considered a thing to be avoided the contents of the bag can be taken through a Haldane set of vessels for absorbing water vapour and carbon dioxide and the total carbon dioxide determined by weighing.”

1910s, Basal metabolism, Diagram, Spirometer

Spirometer and metabolic apparatus, Krogh, 1916

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Spirometer_Metabolic_Apparatus_Krogh_1916

From: The respiratory exchange of animals and man by August Krogh, 1916, page 40.

“Krogh’s apparatus (fig. 15) [1913] which is a modification of an instrument constructed by Haldane and Douglas [1912], is furnished with valves and the air is circulated by the respiratory movements of the subject.  Carbon dioxide is absorbed in a vessel containing a charge of soda lime sufficient to absorb 1000 liters of carbon dioxide, a quantity produced by a man at rest in about 70 hours.  The recording spirometer gives a quantitative record of the respiratory movements and governs the admission of oxygen by closing an electric circuit at (5).  The oxygen from the cylinder is measured by the meter which records electrically by closing a circuit each time a certain quantity has been admitted.  Whenever an experiment has to be extended over a long period, or if the absorption of oxygen is very rapid as during heavy muscular work, the oxygen admitted must be nearly pure to prevent the oxygen percentage in the small apparatus from falling.

“The apparatus in its present form does not allow the direct determination of carbon dioxide.  When such determinations are desired samples of expired and inspired air are drawn from the vessels (2) and (10).  The respiratory quotient is determined by analysing these samples for carbon dioxide and oxygen.  The total respiratory exchange can also be measured over short periods by by multiplying the analytical results by the ventilation as measured from the graphic record.”

1920s, Diagram, Spirometer

Spirometer, McDowall, 1928

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Spirometer_McDowell_1928

From: Proceedings of the Physiological Society, October 13, 1928.  Article “A new volume recorder” by RJS McDowall.

“The principal is an old one, being that of the spirometer and other similar apparatus with a fluid seal, but by improvement of the design friction is reduced to a minimum, while the curvature of the bell permits a large excursion of the lever.  The center of the curvature of the bell and of the weight is at the fulcrum, and if the center of gravity of the lever system is also exactly at the fulcrum the lever and bell are balanced in all positions, and for all practical purposes the entrance of equal amounts of air into the bell is recorded by equal excursions.  The apparatus cannot leak.  It is made by C.F.Palmer.”

1920s, Diagram, Spirometer

Spirometer, Gas Meter Calibration, 1920

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Spirometer_Calibration_Krogh_1920

From: The calibration and accuracy of gas meters. By August Krogh.  Biochemical Journal, 1920, Chapter XXIX, page 19.

“The calibration spirometer (fig 1) is an adaptation of a similar instrument employed by the Dannsk Maalerfabrik, the chief improvement being that I have arranged an automatic record of the volume per revolution of the meter calibrated.  The drum (1) which is as nearly as possible cylindrical is suspended by a band of soft steel and counterbalanced by the adjustable weight (2).  It moves up and down with a minimum of friction.  When the drum is in its highest position the weight can be held by an electromagnet (not shown in the figure) from which it can be released at any desired moment by breaking the current.  Along the steel band a fine brass wire is arranged carrying a number of lead weights (3).  These can be displaced along the wire and a complete equilibrium in all positions of the drum can thus be secured.  When the weight (2) is reduced, any desired pressure up to 20 mm. water can be produced in the spirometer.  The revolving fan (4) which can be driven from outside is used for mixing purposes.  In calibration work with air it is revolved for a few minutes when the spirometer has been filled, to secure a uniform temperature and perfect saturation of the air with water vapour.

“The drum is painted inside and out with a hydrophobe compound so that its volume will not be altered by water absorbed to its wall.  This detail is very important. When left in contact with water, ordinary paint will take up a considerable volume of water which cannot drain off.  According to experiments a painted tinplate continued to gain in weight while immersed in water for a couple of months, ultimately to the extent of 2.5 gm per 100 sq. cm.  Such an increase would in my spirometer diminish by 3.5 cc the effective volume per cm.

“The spirometer drum has been calibrated by measuring a large number of internal diameters (133) evenly distributed over the whole length and circumference of the drum.  These measurements have given as the average diameter 450..135 +/- 0.09 mm or a volume of 1591.4 cc per cm. height.  When the drum is used in the spirometer a lowering of 1 cm. will drive out a little more air than the corresponding volume of the drum because the surface of the water in the reservoir will be raised when 1 cm. of wall of the the drum is lowered into it.  The volume of 1 cm. of the wall of the drum is 9.4 cc.  The rise in the water level will of, course, correspond to 9.4 cm., but since only 19.0% of the water surface is inside the drum the extra volume corresponding to 1 cm. will be 19/100 x 9.4 = 1.8 cc and the effective volume of 1 cm. is therefore 1593.2 cc.  A further correction for the volume of the hydrophobic paint and for water adhering to the inside reduced the volume to 1593.0 cc.  This latter correction is of course a little arbitrary.  When the drum has been rapidly raised the water must be allowed to drain off for about 5 minutes before a practically constant volume is attained.  The water adhering to it at first may amount to a couple of cc. per cm. or more.”

1890s, Diagram, Spirometer

Spirometer, Denison’s, 1890

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Spirometer_Denisons_1890

Invented by Charles Denison.  From: The Sanitarian. Volume 25, 1890, page 408.  “The spirometer I here show you is of my own experimenting, and I will trust it will commend itself to you as a faithful measurer of vital capacity.  When full it is a hollow cylinder, 11.28 inches in diameter, standing on end, the two ends being closed, and the sides made of one piece of light, impervious cloth.  The structure is so light as to give little or no resistance to the expired breath.  That resistance when desired, however, is intended to be used and measured by weights placed on top of the cylinder, or by a manometer attached, so as to determine the expelling force, in pounds pressure, that each individual may have.”