A comparison of methods of obtaining alveolar air / Walter M. Boothby, M.D., and Francis W. Peabody, M.D. Boston.

  • Boothby, Walter M.
Date:
1914
Catalogue details

Licence: In copyright

Credit: A comparison of methods of obtaining alveolar air / Walter M. Boothby, M.D., and Francis W. Peabody, M.D. Boston. Source: Wellcome Collection.

    4/16 (page 2)
    one from an expiration beginning at the end of normal inspiration, the other from an expiration beginning at the end of normal expiration. The values of the two samples are averaged. This method is without doubt the best and simplest for the trained subject. For an untrained person, and especially for one of moderate intelligence, the use of the tongue in closing the mouthpiece presents an almost insurmountable difficulty. To overcome this we have modified the technic by introducing a specially constructed valve. THE HALDANE METHOD WITH A SPECIALLY DESIGNED VALVE The general objection to the use of a valve is that currents and eddies of air are formed which probably introduce a real element of uncertainty. While this is certainly true of the ordinary valve, we believe that the one to be described effectually overcomes this difficulty, and greatly increases the usefulness of the Haldane method. The valve is a hollow copper cylinder about 4 inches in diameter and 1 inch long, closed at both ends. Set into each end of the cylinder, and opposite each other, are two brass tubes of %-inch diameter. Inside the main cylinder is another cylinder, ground so as to fit accurately, which revolves through an arc of about 45 degrees. The inside cylinder is pierced by two %-inch tubes, one of which is open at both ends, and so placed that when set opposite the two tubes previously mentioned a mouthpiece and straight tube about 4 inches long is formed. The far end of the tube is attached to a rubber hose 4 feet long, as in the ordinary Haldane alveolar air-tube. A single, almost instantaneous movement by means of a handle throws the second tube of the inner cylinder into communication with the mouthpiece. This tube is open at the side and closed at the far end, an arrangement which allows the subject to breathe naturally through the mouthpiece to the outside air with a dead space of not over 20 cm. The apparatus is used as follows: The subject breathes naturally for five minutes through the mouthpiece directly to the outside air. At a given signal, at the end either of inspiration or of expiration, the observer turns the handle quickly and puts the subject into communica¬ tion with a 4-foot tube that is perfectly straight and smooth. At the same instant the subject expires as deeply and rapidly as possible, and at the very end of the expiration the observer turns the handle back. The subject now breathes to the outside air and the alveolar air is sealed in the rubber tube. The sample is then quickly drawn into the sampling- pipet. This method has proved itself to be of great value and we invariably use the valve when we are taking alveolar air by the Haldane method.