A Simple Spirometer.

Abstract

In attempting to carry out the laboratory exercises on the volumetric changes in respiration one often finds large sections of elementary students in classes with perhaps a single rather high priced and somewhat delicate piece of apparatus—the Spirometer. A rather simple and seemingly sufficiently accurate piece has been devised which can easily be assembled by appropriating glassware found at hand.

Two large battery jars, 10 liters capacity, are filled two-thirds full of tap water taking care that the level of the water is the same in each jar. A 1000 cc. graduate cylinder is also filled with water and inverted in one of the jars, taking care that no air is allowed to enter on inversion. The respired gasses to be measured are collected by displacement. The delivery tube for the purpose is assembled and consists of a glass mouth-piece of 10 mm. bore of convenient length connected to some length of rubber tubing, which in turn is joined to a ‘Y' tube of the same size. The 2 tubes of the Y are each connected by rubber tubing to other Y tubes of approximately 7 mm. bore. A third series of Y tubes of approximately 4 mm. bore serve to attach the delivery tubes of 2 mm. bore and which are approximately 30 cm. long. By immersing 8 small delivery tubes to the bottom of the partially filled battery jars and by blowing forcefully as in testing vital capacity in the usual way the gas from one tube is collected in the graduate cylinder. Assuming that each tube delivers approximately one-eighth of the total gas escapement in the experiment the total volume can easily be computed.

The coefficients of correlation found between results in this spirometer and results in the Tyces and Sanborn commercial spirometer are +0.85 and +0.88 respectively, computed on the basis of 154 cases.