A respiration recorder / by W.D.M. Paton.

  • Paton, William D. M.
Date:
[1949?]
Catalogue details

Licence: In copyright

Credit: A respiration recorder / by W.D.M. Paton. Source: Wellcome Collection.

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    [From the Proceedings of the Physiological Society, 19 February 1949.] Journal Physiology, Vol. 108. A respiration recorder. By W. D. M. Paton. National Institute for Medical Research, Hampstead, London, N.W. 3 The apparatus provides a compact instrument for use with cats; it records on the smoked drum, the height of the record above the base-line being directly proportional to the respiratory minute volume; it does not need repeated calibration; and it offers little resistance to respiration. The principle involved is simply explained by an electrical analogy. If charge flows continuously into a capacity, from which it can leak away through a resistance, the potential in the capacity rises exponentially to a limiting value which is a measure of the rate of flow of charge. If the flow of charge is intermittent, the system acts as a smoothing device. Here the flow of ' charge 5 is the expiratory minute volume of the animal (F l./min.). The 'capacity5 is a float recorder (C) (Fig. 1); this also records directly the £ potential 5 or pressure within it by the rigidly attached frontal writing lever, since the pressure is proportional to the height (P cm.) of the tracing. The 'resistance5 (R) is a variable leak consisting of a brass rod sliding within a glass tube. Certain constructional details require mention: (1) the float recorder is made of Perspex 2 mm. thick, cross-section 6*8 x 5-8 cm. and 7 cm. deep at its widest rend. This end is covered with a layer of paraffin wax 15 mm. thick to give it additional weight. It is counter-weighted so that with no air flow the recorder is near the bottom of its excursion. The aluminium writing lever terminates 18*5 cm. from the pivot in a writing point 63 mm. long. (The dimensions given are not critical.) (2) The variable leak consists of a brass rod 6-34 mm. diameter in a glass tube of inside diameter 6*88 mm. There is appreciable play of the rod in the tube, and a centring device is necessary; a thin brass triangle making three-point contact on the inside of the tube is screwed to the end of the rod in the tube, and a bearing attached to the tube carries the other end. If the rod or the tube is not quite uniform in diameter, they may be marked so that the alinement at the time of calibration is maintained.