THE CONTROL OF RESPIRATION (Cont'd) 

 PERIODIC BREATHING 



Types of Periodic Breathing 



In the best known. of these, called Cheyne-Stokes respiration, a period 

 of hyperpnea supervenes upon one of apnea, each period following in 

 regular sequence. After an apneic period, the breathing begins at first 

 faintly, gradually becomes more pronounced until it is markedly exag- 

 gerated, and then fades off again to the apneic pause. Sometimes the 

 apneic period is immediately followed by one of intense hyperpnea, there 

 being no gradual 'increase 'In the respiratory movements. Between these 

 two types all varieties of the condition are met (Fig. 132). 



The conditions in which periodic breathing occurs may be divided into 

 physiologic and pathologic groups. Of the physiologic conditions the 

 following may be taken as examples: (1) Breathing in an atmosphere 

 containing a deficiency of 2 ; thus, periodic breathing is very readily 

 produced in persons living in rarefied air. (2) The initial breathing fol- 

 lowing an apnea induced by forced ventilation of the lungs. In this post- 

 apneic periodicity, the apneic periods may at first be quite marked, but 

 as breathing returns they become gradually shorter and the breathing 

 intervals gradually longer, until normal respiration is restored (Fig. 

 131). (3) Breathing through a long tube having a small vessel contain- 

 ing soda lime inserted between the tube and the mouth, the Avhole capacity 

 of this vessel and tubing being about a liter. This will cause periodic 

 breathing in persons that are susceptible to oxygen deficiency. Even 

 breathing through the tube without soda lime will sometimes cause a 

 periodic type of breathing in such individuals. 



The pathologic conditions in which periodic breathing becomes devel- 

 oped are particularly those associated with renal disease and cerebral 

 hemorrhage. In many of these cases, the periodic breathing does not 

 appear to depend on the same factors as are concerned in the experi- 

 mental types. The symptoms would rather appear to depend on some 

 influence of the higher cerebral (supranuclear) centers on the respiratory 

 center. At least some other evidence of disturbance of the cerebral func- 

 tions is always forthcoming, such as a slight paralytic shock, and the 



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