I08 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 63 



IMPORTANCE OF VENTILATION 



The first desideratum in tuberculo-therapy and in the prevention 

 of tuberculosis is abundant and free ventilation. The dwelling, the 

 bedroom, the workshop, the office, the church, the schoolroom, the 

 theatre, the modern subway are one and all dangerous in proportion, 

 as their atmosphere is composed of dead or rebreathed air. Not 

 only is tuberculosis favored by unhygienic surroundings and vitiated 

 atmosphere in particular, but no other agent, not excepting alcohol 

 and bad food, so surely undermines the constitution and renders 

 it unable to resist disease. Air that has once been breathed, ought 

 not to be breathed again. Out of doors the danger is minimized ; 

 indoors we usually breathe and rebreathe the contained air again 

 and again. To some extent, of course, this cannot be avoided, but 

 we should endeavor to reduce it to a minimum. This subject has 

 been recently investigated by Dr. Thomas R. Crowder, who studied 

 by ingenious methods the elTect of such factors as change of posi- 

 tion, body motion, different types of breathing and different tempera- 

 tures and, in addition, has determined the conditions that obtain on 

 the sleeping porch and in the open air. Nasal breathing was the 

 type examined, since in mouth breathing there is, under favorable 

 circumstances, little reinspiration." 



The conclusions that may fairly be drawn from Crowder's work are 

 that (i) a person remaining quiet and indoors will immediately rebreathe 

 from I to 2 per cent of his own expired air; (2) when lying in bed the 

 percentage is higher, rising to from 4 to 10 per cent, depending on the position 

 assumed wh'ile sleeping. " Nor does sleeping in the open insure pure air 

 for breathing. The same influences here produce the same relative results 

 that they do inside. When one buries his head betw^een pillow and bed clothes 

 for the sake of warmth, reinspiration is inevitable, and it is not necessarily 

 small in amount." In addition, it must be noted that at each inspiration we 

 reinhale not only some of the air just exhaled, but also the air contained in 

 the nose and larger bronchi — the so-called " dead-space " air. This may 

 amount to one-third of the whole volume in quiet inspiration and not less 

 than one-tenth in deep breathing. 



The significance of this study in connection with questions of ventilation 

 is obvious. Since even under the most favorable conditions we cannot avoid 

 drawing back into the lungs some of the air that has just passed out of them, 

 not much importance can be attached to the slight variations in carbon 

 dioxide content which occur in the air of rooms. 



^ The Reinspiration of Expired Air. Archives of Internal Medicine, Chi- 

 cago, October, 1913, p. 1936. Journ. Amer. Med. Ass., Editorial, Nov. 29, 1913, 

 p. 1986. 



