CERTAIN SPECIAL TYPES OF RESPIRATION 303 



dioxide is less. It is probable that the cause of apnea is that by rapid in- 

 flations of the lungs impulses pass up by the vagi by means of which in- 

 spiration is after a while inhibited; or that by the repeated stimulation of 

 the center by vagus impulses which result in rapid respiratory movements, 

 anabolism is at last arrested. Apnea is with difficulty produced, if at all, 

 when the vagi are divided. 



Asphyxia. The condition of stress in the respiratory apparatus brought 

 about by insufficient respiratory activity leads to a condition of asphyxia. 

 Progressive asphyxiation may be brought on by anything which interferes 

 with the normal interchange of the respiratory gases of the blood. 



Asphyxia may be produced by the prevention of the due entry of oxygen 

 into the blood, either by direct obstruction of the trachea or other part of the 

 respiratory passages, or by introducing instead of ordinary air a gas devoid 

 of oxygen, or by interference with the due interchange of gases between 

 the air and the blood. 



The symptoms of asphyxia may be divided into three groups, which 

 correspond with the stages of the condition which are usually recognized; 

 these are: i, the stage of exaggerated breathing, hyperpnea; 2, the stage of 

 convulsions, dyspnea; 3, the stage of exhaustion, asphyxiation. 



In the first stage the breathing becomes more rapid and at the same time 

 deeper than usual, the inspirations at first being especially exaggerated and 

 prolonged. This is soon followed by a similar increase in the expiratory 

 efforts being aided by the muscles of extraordinary expiration. This stage is 

 usually called hyperpnea. Hyperpnea soon passes into a condition of labored 

 breathing in which there is marked increase of the force of the expiratory 

 as well as of the inspiratory act, a condition described as dyspnea. All the 

 muscles capable of aiding either directly or indirectly in respiration 

 are ultimately brought into action. These respiratory convulsions are 

 followed by rather sudden onset of paralysis of the respiratory center and 

 death. 



The conditions of the vascular system in asphyxia are: i, more or less 

 interference with the passage of the blood through the systemic and the pul- 

 monary blood vessels; 2, accumulation of blood in the right side of the heart 

 and in the systemic veins; 3, circulation of impure (non-aerated) blood in 

 all parts of the body, especially through the respiratory center. 



Cheyne-Stokes' breathing is a rhythmical irregularity in respirations which 

 has been observed in various diseases. Respirations occur in groups. At 

 the beginning of each group the inspirations are very shallow, but each 

 successive breath is deeper than the preceding, until a climax is reached. 

 The inspirations then become less and less deep, until they cease altogether 

 for a time, after which the cycle is repeated. This phenomenon appears to be 

 due to the want of action of some of the usual cerebral influences w 7 hich pass 

 to, and regulate the discharges of, the respiratory center. 



