1. The composition of a gas mixture can be described by the fractional composition or partial pressure. 2. Alveolar gas composition is determined by alveolar ventilation and the exchange of oxygen and carbon dioxide. 3. Exchange of oxygen and carbon dioxide between the alveolus and pulmonary capillary blood occurs by diffusion. 4. The exchange of gases between the tissues and blood also occurs by diffusion. 5. The amount of alveolar ventilation in relation to pulmonary capillary blood flow—the 6. The composition of the systemic arterial blood is determined by the composition of the capillary blood that drains each alveolus. 7. Right-to-left vascular shunts allow blood to bypass ventilated lung. 8. Part of each breath ventilates dead-space and does not participate in gas exchange. 9. Arterial oxygen (PaO2) and carbon dioxide (PaCO2) tensions are measured to evaluate gas exchange. TABLE 47-1 Common Abbreviations Used in Gas Exchange PO2 decreases at higher altitudes because barometric pressure decreases.
Gas Exchange
ratio—determines the adequacy of pulmonary gas exchange.
The Composition of a Gas Mixture Can Be Described by the Fractional Composition or Partial Pressure
Abbreviation
Definition
AaDO2
Alveolar-to-arterial oxygen tension difference
FiO2
Fraction of oxygen in inspired air
FO2
Fraction of oxygen in the gas mixture
PaCO2
Arterial carbon dioxide tension
PACO2
Alveolar carbon dioxide tension
PaO2
Arterial oxygen tension
PAO2
Alveolar oxygen tension
PB
Barometric pressure
PcapCO2
Capillary carbon dioxide tension
PcapO2
Capillary oxygen tension
PCO2
Carbon dioxide tension
PH2O
Partial pressure of water vapor
PiO2
Inspired oxygen tension
PO2
Oxygen tension
PvCO2
Carbon dioxide tension of venous blood
PvO2
Oxygen tension of venous blood
Mixed venous blood
Perfusion
R
Respiratory exchange ratio
Ventilation
Amount of alveolar ventilation
Rate of carbon dioxide production
Rate of oxygen movement between alveolus and blood
Ratio of alveolar ventilation to blood flow
Exchange of Oxygen and Carbon Dioxide Between the Alveolus and Pulmonary Capillary Blood Occurs by Diffusion
< div class='tao-gold-member'>
You may also need
Full access? Get Clinical Tree
Gas Exchange
Only gold members can continue reading. Log In or Register a > to continue