The factors that determine the values for alveolar pO2 and pCO2 are:
Contents
Following is a list of average partial pressures (in torr) for a human at rest:
Partial pressure of oxygen (at sea level)
The alveolar oxygen partial pressure is lower than the atmospheric O2 partial pressure for two reasons.
The alveolar pO2 is not routinely measured but is calculated from blood gas measurements by the Alveolar gas equation.
Partial pressure of carbon dioxide
The pCO2, along with the pH, can be used to distinguish among metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis.
Pathology
Hypoventilation exists when the ratio of carbon dioxide production to alveolar ventilation increases above normal values.
Hyperventilation exists when the same ratio decreases.
References
Pulmonary gas pressures Wikipedia(Text) CC BY-SA