RESPIRATION 



5S1 



by the increased giving off in the well-ventilated parts, and 

 thus the amount of CO^ in the blood may not be raised, and 

 so the normal stimulus to the respiratory centre may not come 

 into play (fig. 213). 



It has been suggested that iu these conditions the addition 

 of C0„ to the air breathed may have an even more beneficial 

 effect than the addition of oxygen. Possibly a combination 

 would be more efficacious. 



There is some evidence that a sufficient cleariusr out of 

 COo from the blood by forced breathing may so decrease the 

 Ch of the blood, may produce so mai-ked an alkalosis, that the 

 HbOo is not dissociated, and the central nervous system may 

 be so imperfectly supplied with oxj-gen that consciousness may 

 be lost, the arterioles may contract and the heart fail as in 



AciDcsIs 



Fig. 214. — To show the Characters of Cheyne-Stokes Breathing and the 

 factors producing it (see text). 



asjjhyxia. This has been termed by Yandell Henderson 

 aca2ynia. 



In some people and under some conditions a deficient 

 supply of oxygen to the respiratory centre leads to a periodic 

 type of breathing. The patient stops breathing for a time 

 {apncea), then begins to breathe, first quietly, then more 

 forcibly Qiyperpnoea), and, after several respirations, again with 

 decreasing depth till the respirations stop. In these cases, the 

 respiratory centre is less excitable than usual, and it is called 

 into action only when CO 2 has accumulated in the blood. 

 After this accumulation has been got rid of by the forcible 

 respirations, the activity of the centre again wanes. Since the 

 forced breatliing tends to produce excessive clearing out of 

 C0„, it may lead to a decreased dissociation of HbO^ and to a 



