Alveolar Gas Exchange Gas Exchange Volumes and Minute

Alveolar Gas Exchange

Gas Exchange Volumes and Minute Volumes

Determination of Alveolar and Dead Space Ventilation and Volumes If we take FDCO 2 to be zero (b/c room air is defined as zero): Therefore: One way to easily find CO 2 production: Therefore: And:

What Determines PACO 2 (assuming inspired CO 2 = 0)

What Determines PAO 2 Greater alveolar ventilation or higher inspired O 2 gives higher alveolar O 2; Higher rate of oxygen consumption lowers alveolar O 2.

Can We Combine These into One Overall Relationship to Describe Alveolar Gases? c is the same in both equations (=1 / (PB-PH 2 O)): AND Since c = c:

R: The Respiratory Exchange Ratio Unlike RQ, defined at the respiratory exchanger (alveoli) – otherwise, mathematically the same.

Over and Under Ventilation Hyperventilation -- where elimination of CO 2 is greater than production at the tissue level. • Normally considered as a difference between input (from tissues) and elimination (at exchanger) of blood CO 2. • But, we can also consider a sort of hyperventilation that might occur if we over perfuse the tissues where we consider the effects on tissues (? What controls perfusion? ? ) Hypoventilation -- the opposite What are the acid base disturbances associated with hyper- and hypo-ventilation.

Steady and Non-Steady State Ventilation Recall our multiple stage gas exchange model. In steady-state ventilation: In non-steady state, one or more of these will not be equal.

Let's Combine the Notions on the Last Two Slides: AND

CO 2 – O 2 Diagram and Gas Exchange