MASK AND NOSEPIECES, BENEDICT APPARATUS. 189 



MASK AND NOSEPIECES WITH THE BENEDICT RESPIRATION APPARATUS 

 (SPIROMETER UNIT). 



In the earlier development of the Benedict respiration apparatus, 

 several attempts were made to use a mask. This mask was ordinarily of 

 rubber, conical in shape, and held against the face by means of strips of 

 elastic tape bound around the head. About the edge of the mask was 

 rubber tubing which could be inflated. The results obtained with this 

 mask were not very satisfactory and its use was discontinued, mainly 

 on account of the uncertainty as to the air-tight closure about the face. 



As a mask is used in many laboratories in connection with respiration 

 work, it was deemed advisable to make a number of experiments in 

 which the respiratory exchange with the subject wearing a mask was 

 compared with that when he breathed through nosepieces. In this 

 series of comparisons, the spirometer unit was used to measure the 

 respiratory exchange. The mask employed was constructed of sheet 

 lead in the form of a cone, the small end of the cone being soldered 

 to a piece of brass tubing of about 25 mm. internal diameter. The cone 

 was next shaped so as to fit as closely as possible to the face of the 

 selected subject; the superfluous portions were then cut away. The 

 edges of the mask were covered with plasticene, a material used by 

 children in modeling. This mask was connected to the respiration 

 apparatus by means of short pieces of rubber tubing. To make sure 

 of the air-tight closure about the face, the edges of the mask were 

 smeared with soapsuds and kept moist throughout the experimental 

 period ; the slightest leak could thus be readily detected. 



The pulse-rate was obtained with the Bowles stethoscope. A 

 graphic record of the respiration-rate was secured from the movements 

 of the spirometer bell. A similar graphic record of the degree of mus- 

 cular repose w r as obtained by means of the lever bed arrangement 1 in 

 all of the experiments except those with L. E. E. and M. J. S. With 

 the exception of M. J. S., all of the subjects were accustomed to the 

 apparatus. The statistics of the five experiments are given in the 

 following pages. 



STATISTICS OF EXPERIMENTS. 



J. K. M., July 19, 1912. A preliminary experiment to study the possi- 

 bilities of the mask method. Subject had lunch at noon; experiment began at 

 3 h 35 m p. m. Mask, 1 period; pneumatic nosepieces, 1 period. No pulse rec- 

 ords taken; respiration-rate very regular in both periods. Average ^baro- 

 metric pressure, 759.3 mm.; average temperature of air in apparatus, 20 C. 



J. K. M., November 19, 191 2. -^Subject had breakfast before experiment. 

 Mask, 3 periods; nosepieces, 2 periods; preliminary period, 35 minutes; periods 

 with mask and nosepieces in series. Subject asleep in first and third periods 

 with mask. Said he preferred mask, as the nosepieces irritated the edge of 

 the nostrils, but otherwise had no preference. Pulse-rate in first two periods 

 varied considerably, with a range of 5 to 6 beats per minute; in the last three 

 periods it was uniform. Respiration-rate previous to experiment, 19 per min- 

 ute. During experiment respiration regular in depth and rapidity. Average 

 barometric pressure, 762.3 mm. ; temperature of air in apparatus, 22.4 C. 



'See p. 84. 



