Causes of changes in Partial Pressure of Oxygen

Reduced pO2:

–       Later stages of pregnancy

–       Altitude

–       Type 1 respiratory failure (emphysema, PE)

–       Type 2 respiratory failure (muscle disease, chronic bronchitis

–       Methaemoglobinaemia

Reduced pCO2 occurs in

–       Normal pregnancy

–       Hyperventilation

–       Emphysema

–       PE

–       Mild-moderate asthma

Increased pCO2:

–       raised cerebral blood flow

–       raised acidosis

–       therefore more acidic urine