420 ILLINOIS STATE ACADEMY OF SCIENCE 



THE VITAD CAPACITY DETERMINATION 



George Schiff, Northwestern University Medical 

 School, Chicago 



The vital capacity of the lungs is the volume of air 

 which can be expired after the deepest possible inspira- 

 tion. 



Hutchinson, in 1846, invented a spirometer and pointed 

 out its extreme value in the diagnosis of early pulmonary 

 tuberculosis. Until recently, however, the value of the 

 vital capacity determinations was not appreciated, and 

 it is safe to predict that it will not be long before the 

 vital capacity will be an indispensable part of the com- 

 plete physical examination. 



Before the vital capacity determination can be of any 

 practical value, it is essential to have : 



1 — a method and technic which is simple and accurate, 

 and at the same time which is not time consuming, 



2 — a normal standard for comparison, 



3 — a knowledge of the various factors which may in- 

 fluence the vital capacity. 



method 



A spirometer built according to the specifications de- 

 scribed by Peabody permits great accuracy and is best 

 adapted for use with children and adults. The adjust- 

 ment of a self-recording dial is of great advantage, since 

 the entire attention may be given to the proper perform- 

 ance of the test. The subjects stand or sit upright in bed 

 or on a chair, and breathe in and out as deeply as pos- 

 sible through a rubber or glass mouthpiece, the nose being 

 closed by a tight clip. No corrections need be made for 

 temperature, pressure or water tension. 



It is not difficult to obtain satisfactory determinations 

 of the vital capacity in adults, and even children respond 

 with surprising intelligence and ease. Care is taken al- 

 ways to explain to the patients the desired object, and 

 it is necessary to urge them to breathe as deeply as pos- 

 sible. Strict attention should be paid to this point, for 

 otherwise the volume of the respiration will be low ancl 

 will not represent the true maximum of respiratory ex- 



