QuestionSBA
QuestionChoice
This is the assumed PaCO2 used in the alveolar gas equation but is not the alveolar PO2.
10026104
e
40mmHg
QuestionChoice
This is incorrect. This is the partial pressure of water vapour (PH2O).
10026101
b
47mmHg
QuestionChoice
This is incorrect. This is the atmospheric pressure, not the alveolar PO2
10026103
d
760mmHg
QuestionChoice
This is incorrect. It does not represent the alveolar PO2
10026102
c
150mmHg
QuestionChoice
Correct. This is the calculated apparent alveolar PO2 using the alveolar gas equation, taking into account the given FiO2, atmospheric pressure, and assuming a PaCO2 of 40 mmHg and a respiratory exchange ratio of 0.8.

The alveolar gas equation is PAO2 = (FiO2 * (PATM - PH2O)) - (PaCO2 / R), where R is 0.8. Inserting the above values into this equation gives a PAO2 of 100mmHg.
10026100
a
100mmHg
Concept
Chapter
2693
4198
Gaseous exchange and transport
Topic
150
Respiratory physiology
17618
A 16 year old female attends the lung function clinic for spirometry testing.

Her tidal volume is 500ml, respiratory rate 12 breaths/minute. The fraction of inspired oxygen is 0.21.

Atmospheric pressure (PATM) is 760mmHg. The partial pressure of water (PH2O) is 47mmHg and the partial pressure of carbon dioxide (PaCO2) is 40mmHg.

Calculate the apparent alveolar partial pressure of oxygen (PO2) using the alveolar gas equation.
a