Tag: Composition Of Alveolar Air

Composition Of Alveolar Air

Composition Of Alveolar Air


COMPOSITION OF ALVEOLAR AIR

  • Concentrations of gases in alveolar air differ from atmospheric air (inspired air)
  • Atmospheric air contains approximately 21% O2, 79% N2 & 0.04% of CO2.
  • Immediately after inspiration, there is no change in composition.
Factors causing difference:

1. Constant gaseous exchange process

  • Continous removal of oxygen from alveolar air into blood vessels.
  • CO2 addition to alveolar air from blood vessels.

2. Humidification:

  • Dry atmospheric air humidified by upper respiratory passages before alveolar entry.

3. Partial/slow replacement with atmospheric air:

  • Only small amount of fresh air (350 ml) added to alveolar air (2.2 L) during each inspiration.
  • Slow replacement of atmospheric air into alveolar air happens.
  • Advantages:
  • Prevents sudden changes in gas concentrations in blood.
  • Stabilizes respiratory control mechanism.
  • Prevents excessive fluctuation in tissue oxygenation, CO2 concentration, & tissue pH, 
Gaseous concentration & its partial pressure in alveoli:
1. Oxygen: 
Concentration & partial pressure controlled by, 
  • Rate of absorption of O2 into blood
  • Rate of entry of new Ointo lungs by ventilatory process.
Values:
  • Partial pressure of O2 in inspired air (Pi O2)
  • 158 mm Hg
  • Partial pressure of O2 in alveolar air (PO2)
  • 100 mm Hg
  • Calculated by “Alveolar gas equation”.
  • Partial pressure of O2 in expired air (PO2)
  • 116 mm Hg

2. Carbon-di-oxide:

  • Partial pressure of CO2 in inspired air (Pi CO2)
  • 0.3 mm Hg
  • Partial pressure of CO2 in alveolar blood (PA CO2)
  • 40 mm Hg
  • Partial pressure of CO2 in expired air (PE CO2)
  • 32 mm Hg
Exam Question
 

COMPOSITION OF ALVEOLAR AIR

Factors causing difference:

  • Constant gaseous exchange process
  • Humidification:
  • Partial/slow replacement with atmospheric air:
Gaseous concentration & its partial pressure in alveoli:
1. Oxygen:
  • Partial pressure of O2 in inspired air (Pi O2)
  • 158 mm Hg
  • Partial pressure of O2 in alveolar air (PO2)
  • 100 mm Hg
  • Calculated by “Alveolar gas equation”.
  • Partial pressure of O2 in expired air (PO2).
  • 116 mm Hg

2. Carbon-di-oxide:

  • Partial pressure of CO2 in inspired air (Pi CO2)
  • 0.3 mm Hg
  • Partial pressure of CO2 in alveolar blood (PA CO2)
  • 40 mm Hg
  • Partial pressure of CO2 in expired air (PE CO2)
  • 32 mm Hg.
Don’t Forget to Solve all the previous Year Question asked on Composition Of Alveolar Air

Composition Of Alveolar Air

COMPOSITION OF ALVEOLAR AIR

Q. 1

What is the partial pressure for oxygen in the inspired air?

 A

116 mm Hg

 B

158 mm Hg

 C

100 mm Hg

 D

0.3 mm Hg

Q. 1

What is the partial pressure for oxygen in the inspired air?

 A

116 mm Hg

 B

158 mm Hg

 C

100 mm Hg

 D

0.3 mm Hg

Ans. B

Explanation:

Partial pressure of O2 in inspired air (Pi O2) – 158 mm Hg

Gaseous concentration & its partial pressure in alveoli:
1. Oxygen: 
Concentration & partial pressure controlled by, 
  • Rate of absorption of O2 into blood
  • Rate of entry of new O2 into lungs by ventilatory process.
Values:
  • Partial pressure of O2 in inspired air (Pi O2)
    • 158 mm Hg
  • Partial pressure of O2 in alveolar air (PA O2)
    • 100 mm Hg
    • Calculated by “Alveolar gas equation”.
  • Partial pressure of O2 in expired air (PE O2)
    • 116 mm Hg

2. Carbon-di-oxide:

  • Partial pressure of CO2 in inspired air (Pi CO2)
    • 0.3 mm Hg
  • Partial pressure of CO2 in alveolar blood (PA CO2)
    • 40 mm Hg
  • Partial pressure of CO2 in expired air (PE CO2)
    • 32 mm Hg

Q. 2

What is the partial pressure for oxygen in the expired air?

 A

116 mm Hg

 B

158 mm Hg

 C

100 mm Hg

 D

0.3 mm Hg

Q. 2

What is the partial pressure for oxygen in the expired air?

 A

116 mm Hg

 B

158 mm Hg

 C

100 mm Hg

 D

0.3 mm Hg

Ans. A

Explanation:

Partial pressure of O2 in expired air (PE O2) – 116 mm Hg

Gaseous concentration & its partial pressure in alveoli:
1. Oxygen: 
Concentration & partial pressure controlled by, 
  • Rate of absorption of O2 into blood
  • Rate of entry of new O2 into lungs by ventilatory process.
Values:
  • Partial pressure of O2 in inspired air (Pi O2)
    • 158 mm Hg
  • Partial pressure of O2 in alveolar air (PA O2)
    • 100 mm Hg
    • Calculated by “Alveolar gas equation”.
  • Partial pressure of O2 in expired air (PE O2)
    • 116 mm Hg

Q. 3

What is the partial pressure for oxygen in the alveolar air?

 A

116 mm Hg

 B

158 mm Hg

 C

100 mm Hg

 D

0.3 mm Hg

Q. 3

What is the partial pressure for oxygen in the alveolar air?

 A

116 mm Hg

 B

158 mm Hg

 C

100 mm Hg

 D

0.3 mm Hg

Ans. C

Explanation:

Partial pressure of O2 in alveolar air (PA O2) – 100 mm Hg.

Gaseous concentration & its partial pressure in alveoli:
1. Oxygen: 
Concentration & partial pressure controlled by, 
  • Rate of absorption of O2 into blood
  • Rate of entry of new O2 into lungs by ventilatory process.
Values:
  • Partial pressure of O2 in inspired air (Pi O2)
    • 158 mm Hg
  • Partial pressure of O2 in alveolar air (PA O2)
    • 100 mm Hg
    • Calculated by “Alveolar gas equation”.
  • Partial pressure of O2 in expired air (PE O2)
    • 116 mm Hg

Q. 4

What is the partial pressure for carbon-di-oxide in the alveolar blood?

 A

0.3 mm Hg

 B

40 mm Hg

 C

32 mm Hg

 D

158 mm Hg

Q. 4

What is the partial pressure for carbon-di-oxide in the alveolar blood?

 A

0.3 mm Hg

 B

40 mm Hg

 C

32 mm Hg

 D

158 mm Hg

Ans. B

Explanation:

Partial pressure of CO2 in alveolar blood (PA CO2) – 40 mm Hg.

Carbon-di-oxide:

  • Partial pressure of CO2 in inspired air (Pi CO2)
    • 0.3 mm Hg
  • Partial pressure of CO2 in alveolar blood (PA CO2)
    • 40 mm Hg
  • Partial pressure of CO2 in expired air (PE CO2)
    • 32 mm Hg

Q. 5

What is the partial pressure for carbon-di-oxide in the inspired air?

 A

0.3 mm Hg

 B

158 mm Hg

 C

100 mm Hg

 D

32 mm Hg

Q. 5

What is the partial pressure for carbon-di-oxide in the inspired air?

 A

0.3 mm Hg

 B

158 mm Hg

 C

100 mm Hg

 D

32 mm Hg

Ans. A

Explanation:

Partial pressure of CO2 in inspired air (Pi CO2) – 0.3 mm Hg

Carbon-di-oxide:

  • Partial pressure of CO2 in inspired air (Pi CO2)
    • 0.3 mm Hg
  • Partial pressure of CO2 in alveolar blood (PA CO2)
    • 40 mm Hg
  • Partial pressure of CO2 in expired air (PE CO2)
    • 32 mm Hg.

Q. 6

What is the partial pressure for carbon-di-oxide in the expired air?

 A

0.3 mm Hg

 B

158 mm Hg

 C

40 mm Hg

 D

32 mm Hg

Q. 6

What is the partial pressure for carbon-di-oxide in the expired air?

 A

0.3 mm Hg

 B

158 mm Hg

 C

40 mm Hg

 D

32 mm Hg

Ans. D

Explanation:

Partial pressure of CO2 in expired air (PE CO2) – 32 mm Hg

Carbon-di-oxide:

  • Partial pressure of CO2 in inspired air (Pi CO2)
    • 0.3 mm Hg
  • Partial pressure of CO2 in alveolar blood (PA CO2)
    • 40 mm Hg
  • Partial pressure of CO2 in expired air (PE CO2)
    • 32 mm Hg.


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