Link to glossary: Glossary Symbols of Respiratory Physiology
This lecture starts off with reiterating on the last lecture. It touches on lung compliance, airways resistance and dynamic compression of airways again. Additionally work of breathing rehashing. Asks what would lead to a hypoventilating patient.
Gas exchange
Lecture denotes how generally a patient will consume O₂ at a rate of 250-300 ml/min and produce CO₂ at a rate of 200-250ml/min. However this needs to be able to be increased in exercise.
Components of alveolar diffusion
Additionally a constant called the Respiratory Exchange Ratio (R) = 0.8 = 200/250. So for every 1ml of oxygen we inhale we exhale 0.8ml CO2 this is due to making water and that carbs supply their own oxygen etc
PAO2 and PACO2 are half of alveolar diffusion a.k.a. it sets the alveolar end. The other is arterial gas pressures.
We cannot measure alveolar gas composition so we must calculate it using the composition of inspired air (PI, alveolar ventilation, O2 consumption and CO2 production, and V=Q. Oxygen is like a balancing game between VA, PIO2 coming in and VO2 going into blood. Carbon dioxide is a balancing game of VA, PICO2 going out and VCO2 coming in
Oxygen
Carbon dioxide
N.B. PICO2 is 0 The alveolar gas equation is thus:
and the ∆A-a as a determinant of decreased diffusion. is it is more than 10 it means there is less gas exchange
and additionally the only things are introducing in this equation (at room air ventilation) is PaO2 and PaCO2. therefore you can figure it all out from this