A variety of bags and balloons had been used to collect exhaled air during the 1800’s. Little consideration was made however, was made to how permeable the bag material was. Douglas’ bag was intended for measuring gas exchange and his innovation was to make it out of impermeable material (rubberized canvas). The Douglas bag has been used for a variety of purposes ever since.
Douglas Bag, 1916. From: The respiratory exchange of animals and man by August Krogh, 1916, page 42.
“Regnard  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 ) 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.”
Douglas Bag, 1920. From: The Newer Methods of Blood and Urine Chemistry, by By Rutherford Birchard Hayes Gradwohl, Abraham Jacob Blaivas, 1920, Page 373.
“The Douglas Bag. The Douglas Bag is made of rubber-lined cloth, and is capable of holding from 50 to 100 liters. It is especially useful for investigations during exercise, since it is fitted with straps so that the bag can be fastened to the shoulders (Fig. 73). It is then connected with the valves, the mouthpiece of which is placed between the lips. Respirations are commenced with the three-way valve turned so as to allow the expirations to pass directly outside. After respiratory equilibrium is established, the three-way valve is turned during an inspiratory period so that the succeeding expirations may pass into the bag. The time required to fill the bag comfortably is determined with a stop-watch. The air which has been collected in the bag during the period is thoroughly mixed and passed through a meter, the temperature and barometric pressure are noted, and a sample analyzed in the Haldane gas apparatus. The bag should be emptied completely by rolling it up when nearly empty.”
Douglas Bag, 1921. Shown with a Haldane apparatus for gas analysis. From a 1921 catalog, Laboratory Apparatus and Reagents Selected for Laboratories of Chemistry and Biology, from Arthur H. Thomas Co, page 367.
Douglas Bag, 1921. From a 1921 catalog, Laboratory Apparatus and Reagents Selected for Laboratories of Chemistry and Biology, from Arthur H. Thomas Co, page 367.
Douglas Bag, 1921. From Basal Metabolism: Its determination and application. Frank Sanborn editor. Sanborn Company Publishers, 1922. Page 54.
Douglas Bags, 1924, For Exercise. From “Muscular Exercise, Lactic Acid, and the supply and utilization of oxygen, part IV – VI”, by A.V. Hill, C.N.H. Long, H. Lupton. Proceedings of the Royal Society of London, Volume 97, number 681, page 87.
Douglas Bag, 1925. From: The respiratory response to carbon dioxide. By HW Davies, GR Brow, CAL Binger. Journal of Experimental Medicine, 1925, page 38.
“The effect of gradually increasing percentages of carbon dioxide was studied by means of rebreathing in a closed circuit consisting of a modified Douglas Bag with inflow and outflow tubes, a dry meter, and a rubber mouthpiece fitted with inspiratory and expiratory valves. The general arrangement of the apparatus is shown semidiagrammatically in text-fig. 1. The direction of airflow is indicated by means of arrows. A is the modified Douglas Bag of 100 liters capacity. B, B’ are wide bored three-way taps. C is the mouthpiece. D is a twenty-light capacity “B-type” dry meter manufactured by D. MacDonald and company of Albany. The resistance of this meter is almost negligible even at the maximal rates of pulmonary ventilation produced by high percentages of carbon dioxide in the inspired air. E is a small bore side tube connected with an oxygen tank fitted with reducing valve and a flow meter calibrated with approximate accuracy rates of flow of less than 1 liter per minute. A similar side tube, F, is used to obtain samples of inspired air, either into exhausted sampling tubes or directly into the burette of the Haldane gas analysis apparatus. By way of the three-way stop cocks B,B’ the subject may be made to inhale from and exhale into the room air through the meter, and his normal respiratory rate and minute volume may be determined. When the stop-cocks are turned the apparatus becomes a closed circuit, inspiration and expiration being from and to the Douglas Bag, A.”
Douglas Bag, 1928. A rather ingenious technique. Douglas bags being used to collect exhaled air from a runner. Found posted on www.fact.canada.com. Original source is unknown.
Douglas Bag, 1934. Found at Europeana.Eu. From an educational film entitled “Methods of measuring metabolism and basal metabolism Krogh and Douglas bag”, Produced by the Department of Physiology, Cambridge University, 1934. A comparison of filled Douglas bags, one from a resting test and one from an exercise test.
Douglas Bag, 1934. Found at Europeana.Eu. From an educational film entitled “Methods of measuring metabolism and basal metabolism Krogh and Douglas bag”, Produced by the Department of Physiology, Cambridge University, 1934. Douglas bag shown filled following an exercise test.
Douglas Bag, 1934. Found at Europeana.Eu. From an educational film entitled “Methods of measuring metabolism and basal metabolism Krogh and Douglas bag”, Produced by the Department of Physiology, Cambridge University, 1934. Demonstrating how to empty a Douglas Bag.
Douglas Bag, 1942, Altitude Research. Douglas bag used to measure oxygen consumption in altitude research. From Popular Science Magazine, May 1942. “How flyers are redesigned. Air Surgeons groom men for survival at high altitude”, page 116.
Douglas Bag, 1942, Altitude Research. Douglas bag used to measure oxygen consumption in altitude research. From Popular Science Magazine, May 1942. “How flyers are redesigned. Air Surgeons groom men for survival at high altitude”, page 117.
Douglas Bag, circa 1940’s. Undated photo of a Douglas bag being used to capture exhaled air while the subject loads torpedoes, probably from the 1940’s. Found on a ScienceDawn.com article.
Douglas Bag, 1945. From Bioenergetics and Grown by Samuel Brody, Published by Reinhold Publishing, NY, 1945. Chapter 12, page 337. Found on the website BeefEfficiency.org.
Douglas Bag, circa 1950’s. Undated photo found on the FAO Corporate Repository. Probably from the 1950’s.
Douglas Bag, 1970, Skiing. Attributed to an unnamed 1970 article by Astrand and Rodahl.
Douglas Bag, Basal Metabolism, 2001. From Kinanthropometry and Exercise Physiology Laboratory Manual: Volume 2: Exercise Physiology: Tests, Procedures and Data, by Roger Eston, Psychology Press, 2001, page 141.
Douglas Bag, 2007. Being used to collect exhaled air in order to measure oxygen consumption. From “Indirect Calorimetry: A Practical Guide for Clinicians”, Nutrition in Clinical Practice, 2007, 22(4): 277-388.
PFT History by Richard Johnston is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.