CRITICAL DISCUSSION OF RESPIRATION APPARATUS. 253 

 PNEUMATIC NOSEPIECES. 



The breathing apparatus used most frequently in this laboratory is 

 the pneumatic nosepiece, 1 which was devised in connection with the 

 development of the Benedict respiration apparatus in an attempt to 

 secure some breathing appliance which could be used by practically 

 all subjects. Before this time a glass nosepiece, such as that used by 

 Tissot, and a rubber mouthpiece of the Denayrouse form had been 

 tried. Neither of these appliances gave markedly successful results, 

 as it was found difficult to make them air-tight. 



The deflated pneumatic nosepieces are inserted in the nose and air 

 pressure applied until the rubber is inflated sufficiently to fit closely 

 into all of the inequalities of the nostrils. These nosepieces have given 

 very satisfactory results. They are easily made from materials which 

 are readily obtained, such as rubber finger cots, rubber stoppers, glass 

 tubing, and rubber tubing, but considerable time is required for their 

 construction. The nosepieces are flexible and nearly every type of 

 nostril can be fitted without great discomfort. This has been proved 

 repeatedly in the Nutrition Laboratory by the fact that many of the 

 subjects with whom they have been used have fallen asleep easily. 



The nosepieces when inserted may be tested for leaks around the 

 nostrils by a simple method. The subject draws air in through the 

 nose, then closes with the hands the ends of the attachment to which the 

 nosepieces are fastened and attempts to exhale through the nose; a 

 leak will be detected by the air which passes out through the opening. 

 The escaping air may be heard if the leak is large or felt against the 

 skin if the hand is placed near the nosepieces. This method of testing 

 is not, however, always absolutely reliable, for occasionally, when 

 pressure is applied from within the nose, the nosepieces apparently 

 fit closely but in use a slight loss of air occurs. This may be due to the 

 fact that in normal breathing there is always a very slight dilation of 

 the outer edge of the soft part of the nostril and this may be sufficient, 

 when air is inhaled, to allow air to pass. 



The best test for tightness is to apply soapsuds with a camel's hair 

 brush, any leakage of air being shown by bubbles. In a series of 

 experiments which are difficult and costly to repeat, the tightness of 

 the nosepieces should be tested in this manner. The soapsuds should 

 be continually applied throughout the experiment, or at least suffi- 

 ciently often so that the space between the nosepieces and the nostrils 

 will always be wet. Although Coleman and Dubois have employed 

 this method in all of their experiments with typhoid-fever patients, it 

 is annoying to some subjects, and if experiments are continued over a 

 long period, as for example, for 12 hours daily, it may produce soreness 

 which will make the subject distinctly uncomfortable. The use of 



x See description on p. 22. 



