There are five primary causes ofhypoxaemia (low blood oxygencontent):
- Diffusion limitation whichlimits the transfer of oxygen between the alveoli and blood (suchas pulmonary oedema).
- Hypoventilation
- Reduced atmospheric oxygen(such as high altitude)
- Ventilation/perfusion (VQ)mismatch (for some reason poorly ventilatedalveoli are still receiving blood flow)
- Shunt- some alveoli arecompletely blocked either by obstruction or are completely filledwith fluid such as in pneumonia, but still receive blood flow.
The first four of these can be helpedby giving the patient oxygen which in turn increases their arterialPO2. However, giving oxygen has little impact on apatient with a pulmonary shunt.
For each of the above causes, briefly(1-2 sentences) describe how itwould lead to low arterial PO2. Then describe why givinga patient 100% oxygen would increase their arterial PO2(for the first four), and why it would not significantly improve ina patient with a pulmonary shunt. Explain your reasoning. 4 and 5are the most challenging and will require more description than thefirst 3. (2-6 total sentenceseach)
Diffusion Limitation :
Hypoventilation :
Reduced atmospheric oxygen :
V/Q Mismatch:
Shunt
