When given high concentrations of O2, a patient with chronic ...

[humphriesbr@me.com]

When given high concentrations of O2, a patient with chronic hypercapnia may develop a more serious respiratory acidosis. Which of the following might be contributing to the patient's in-creased PCO2?
 
  1. Worsening ventilation-perfusion (VV/QQ) balance
  2. Desensitization of the carotid bodies
  3. Removal of the hypoxic stimulus
  a. 1 and 2 only
  b. 1 only
  c. 1 and 3 only
  d. 1, 2, and 3

Question 2

Stimulation to increase ventilation does not occur until the PaO2 falls below what level?
 
  a. 90 mm Hg
  b. 80 mm Hg
  c. 70 mm Hg
  d. 60 mm Hg

[jordangronback]

Answer to Question 1

ANS: C
Nevertheless, the reduction in minute ventilation following O2 breathing in advanced COPD is not always severe enough to account for the increased PaCO2. Some investigators suggest that O2 breathing worsens the VV/QQ relationships in the lungs and is responsible for the increase in PaCO2. Other investigators have suggested that O2-induced hypercapnia is caused by the com-bined effects of hypoxic stimulus removal and redistribution of relationships in the lungs.

Answer to Question 2

ANS: D
When pH and PaCO2 are normal (pH = 7.40 and PaCO2 = 40 mm Hg), the carotid bodies' nerve-impulse transmission rate does not increase significantly until the PaO2 decreases to ap-proximately 60 mm Hg.

[humphriesbr@me.com]

Gracias!

[marict]

Excellent