3. Physiology
        3.13. Respiratory
            3.13.3. Gas carriage
                3.13.3.4. Oxygen
3.13.3.4.1. Oxygen cascade

Oxygen cascade

Partial pressure = Total pressure x concentration (%)

 

Dry air has 20.93% O2.

 

Sea level pressure = 760mmHg

Water vapour pressure = 47mmHg

Thus,

=> Pressure exerted by gas in saturated moist air = 760-47 = 713mmHg

=> Partial pressure of O2 in saturated moist air = 713 x 0.2093 = 149.23mmHg

i.e. PiO2 = 149mmHg

 

 

PaO2 decreases with increasing age from about 20 years old

 

Ideal alveolar gas equation

PAO2 = PIO2 - (PACO2/R) + F

NB:

 



Table of contents  | Bibliography  | Index