Physiology Flashcards
Hypoxemia?
Decreased O2 content of the blood
Decreased PaO2 or decreased O2 Saturation.
Hypoxia?
Condition of low O2 at cellular level
What are the 3 major contributing factors to oxygen delivery?
- 2.
3.
Why is PaO2 clinically relevant?
Marker of how diseased the lungs are.
If SpO2 is around normal but PaO2 is very, very low = severe respiratory dysfunction.
ARDS
What is the difference b/t a normal A-a gradient and a high A-a gradient?
“It’s all about the Alveolus.”
Normal: O2 content in artery matches the O2 content in the alveolus.
High: lots of O2 in the alveolus, but not in an artery -> no gas exchange happening.
What are the 3 major contributory factors to oxygen delivery?
- Air in and out; Blood round and round.
- Diffusion (gas exchange) depends on surface area, distance, pressure difference.
- O2 dependent on diffusion and CO2 dependent on ventilation/convection.
PA-O2?
Alveolar Pressure
PaO2?
Arterial pressure
Causes of Hypoxia?
- Low inspired ppO2 - Altitude.
- Hypoventilation
* decreased RR and Vt.
* Increased Vd. - V/Q Mismatch
- Diffusion D/o
- Full Shunt
Hypoxemia is classified w/ these signs?
PaO2 <60, low O2 sat, Cyanosis.
A normal A-a gradient dependent on?
Normal gas exchange in the alveoli.
What causes a high A-a gradient?
Bad gas exchange or O2 transfer.
Examples of D/o’s that cause a High A-a gradient?
Alveolar membrane D/o’s,
Interstitial Lung Dz (ILD) or
VQ Mismatch D/o’s.
Hypoxemia w/ a normal A-a gradient implies…
Hypoventilation w/displacement of alveolar O2 by CO2 or other substance or
Problems getting air in the alveolus because of Altitude or increased ppO2.
Examples of V/Q Mismatch disorders?
Asthma, Pneumonia, COPD, PE, Pulmonary Edema
