From: Yandell Henderson, AND INDIRECT CALORIMETRY VI. THE RESPIRATORY EXCHANGE APPLICATIONS OF GAS ANALYSIS: ARTICLE: J. Biol. Chem. 1918, 33:47-53.
“A form of valve which has proved convenient has recently been devised at the University of Minnesota by professors A.D. Hirschfelder and E.D. Brown. By their kind permission a diagram of two of these valves arranged for inspiration and expiration on a T-tube is shown in Fig. 2. Each valve is made of a large tin salve box with a disk of sheet rubber inside, held in place by a ring spring wire soldered to the box at one point. The crack around the box is made tight with adhesive plaster. In the figure the cover of one valve is removed to show the rubber and wire.”
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.”
From: The respiratory exchange of animals and man, by August Krogh, 1916, page 42.
“The apparatus of Benedict (fig. 16) [1909, 1912] is arranged to measure both carbon dioxide and oxygen, and the recording spirometer has an attachment (a “work adder”) which automatically adds the excursions together and so records the rate of ventilation. The instrument has no valves, but a rapid circulation of air is maintained by the blower. This is necessitated by the great resistance of the water-vapour absorbers. If this resistance were avoided the apparatus could be simplified considerably.”
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.”
From: The respiratory exchange of animals and man by August Krogh, 1916, page 40.
“Valves such as Muller’s and other fluid valves, generally filled with water or mercury, were formerly used extensively. They have the advantage that leakage backwards is impossible, but their resistance is generally considerable. Zentz uses the “Darmventile” invented by Speck. These are certainly effective and the resistance very slight, but the valves are large and cumbrous. Reliable metal valves with a minimum resistance have been constructed by Chauveau (Tissot, 1904) and by the firm Siebe, Gorman (Douglas, 1911). Bohr constructed rubber valves which, slightly modified, have given entire satisfaction in Danish laboratories (fig. 14).”
From: The respiratory exchange of animals and man by August Krogh, 1916, page 40.
“Masks of rubber which can be fitted on the face and enclose the mouth and nose are far more convenient than mouthpieces, but it is extremely difficult to avoid leakage. Bohr constructed masks which were specially fitted to each person on whom it was intended to experiment. These masks (fig. 13) consist of a funnel-shaped piece of tinplate coated on the edge with a substance used by dentists and know commercially as Stent’s composition. This substance becomes soft at a temperature of about 50 degrees, and can then easily be moulded on the face of a person and can be made to fit absolutely airtight when greased with lanolin, causing at the same time a minimum of inconvenience. These masks are much used in Danish laboratories for all experiments which have to last more than a few minutes at a time.”
The diverse, quirky and mostly forgotten history of Pulmonary Function testing
