What is the primary determinant of the PAO2? a. Body's CO2 b. ...

[Themember4]

What is the primary determinant of the PAO2?
 
  a. Body's CO2
  b. Metabolic rate of the body tissues
  c. PaO2
  d. PO2 in the inspired gas

Question 2

Calculate the approximate PAO2 given the following conditions (assume R = 0.8): FiO2 = .40, PB = 770 mm Hg, PACO2 = 31 mm Hg
 
  a. 100 mm Hg
  b. 135 mm Hg
  c. 250 mm Hg
  d. 723 mm Hg

Question 3

The PAO2 depends on which of the following factors?
 
  1. Ambient (atmospheric) pressure
  2. Fractional concentration of inspired O2
  3. Level of VA
  4. Types of fuels burned (fat, protein, and carbohydrate)
  a. 1, 2, and 3 only
  b. 1 and 2 only
  c. 3 only
  d. 1, 2, 3, and 4

[vkodali]

Answer to Question 1

ANS: D
Many factors determine the alveolar partial pressure of oxygen (PAO2). Most important is the inspired partial pressure of oxygen, or PIO2.

Answer to Question 2

ANS: C
PAO2 = FiO2  (PB  47)  PACO2  0.8
where FiO2 is fraction of inspired oxygen, PB is barometric pressure, 47 is water vapor tension (in mm Hg) at 37 C, PACO2 is alveolar PCO2, and 0.8 is normal respiratory exchange ratio (R).
PAO2 = 0.4(770  47)  (31/0.
PAO2 = 250.45 mm Hg

Answer to Question 3

ANS: D
PAO2 = FiO2  (PB  47)  PACO2  0.8
where FiO2 is fraction of inspired oxygen, PB is barometric pressure, 47 is water vapor tension (in mm Hg) at 37 C, PACO2 is alveolar PCO2, and 0.8 is normal respiratory exchange ratio (R). As the A is the primary determinant of PACO2 any changes in A will affect the PAO2. Likewise the fuel source will determine the RQ which is normally 0.8.