Which of the following can cause Cheyne-Stokes breathing? 1. ...

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Which of the following can cause Cheyne-Stokes breathing? 1. Brain injuries 2. Congestive heart failure 3. Metabolic acidosis
 
  a. 1 and 2 only
  b. 2 and 3 only
  c. 1 and 3 only
  d. 1, 2, and 3

Question 2

Which of the following are causes of central neurogenic hyperventilation? 1. Head trauma 2. Inadequate brain blood flow 3. Severe brain hypoxia 4. Hypothermia
 
  a. 2 and 3 only
  b. 1 and 4 only
  c. 2 and 3 only
  d. 1, 2, and 3 only

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Answer to Question 1

ANS: A
Cheyne-Stokes breathing occurs when cardiac output is low, as in congestive heart failure, de-laying the blood transit time between the lungs and the brain. In this instance, changes in respir-atory center PCO2 lag behind changes in arterial PCO2. For example, when an increased PaCO2 from the lungs reaches the respiratory neurons, ventilation is stimulated; this then lowers the arte-rial PCO2 level. By the time the reduced PaCO2 reaches the medulla to inhibit ventilation, hy-perventilation has been in progress for an inappropriately long time. When blood from the lung finally does reach the medullary centers, the low PaCO2 greatly depresses ventilation to the point of apnea. Arterial PCO2 then rises, but a rise in respiratory center PCO2 is delayed because of low blood flow rate. The brain eventually does receive the high PaCO2 signal and the cycle is repeat-ed. Cheyne-Stokes respiration may also be caused by brain injuries in which the respiratory cen-ters overrespond to changes in the PCO2 level.

Answer to Question 2

ANS: D
Central neurogenic hyperventilation is characterized by persistent hyperventilation driven by ab-normal neural stimuli. It is related to midbrain and upper pons damage associated with head trauma, severe brain hypoxia, or lack of blood flow to the brain.

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