An Electronically Modified Wet Spirometer

Journal/Book: Reprinted from Nature Vol. 207 No. 4997 pp. 643-645 August 7 1965. 1965;

Abstract: Department of Anatomy Now York Medical College New York 29. IN a recent investigation of respiratories recordings were made simultaneously from multiple indwelling electrodes along with spirometrie tracings so that electrical activity could be examined in a series of conscious rabbits during quiet respiration. The electrical signals from the muscles and the spirometric tracing are shown on a film record (Fig. 1). Attention is directed especially to the spirometric tracing which appears as a horizontal band which widens with expiration and narrows with inspiration. A primary interest was to secure an accurate reflexion of the movement of air into and out of the lungs of the rabbit a factor dependent on the accuracy of the spirometer. Although many spirometers are available a simple inexpensive electronic modification of a wet spirometer (400-c.c. Phipps and Bird spirometer Richmond Va.) was developed (Fig. 2). The electronic modification of the spirometer its application and a method devised to determine its latency from the subject of this communication. The spirometer is designed so that its lower cylinder can be filled with water and its inverted floating cylinder filled with air. A metal tube within the lower cylinder is connected to an external primary T-tube and carries respiratory gases above the water line and into the floating cylinder. A secondary T-tube is inserted into another vessel containing soda-lime for the absorption of carbon dioxide. The two T-tubes are interconnected by a rubber tube 10 cm long and 5 mm inside diameter. The other end of the primary T is connected to an oxygen tank by means of a similar rubber tube. Another tube 35 mm long and 5 mm inside diameter loads from the remaining arm of the secondary T to the stem of a Y-tube the arms of which are equipped with a pair of rubber tubes 7·5 cm long. Flexible plastic foetal catheters 4 mm inside diameter and 5 cm long are inserted into the tips of the last-mentioned tubes. The catheters which are passed into the rabbit's nares during recording sessions are coated with a topical anaesthetic ointment ('Tronothane hydrochloride') which serves to desensitize the nasal passages as well as to prevent any possible leakage of air around the catheters. ... ___MH

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