This may seem like a pretty easy topic and, I agree, it is easy to memorise the step wise decreases in oxygen tension as you move from the atmosphere to the the tissue.
Why to these changes occur? Have you thought about the implications, on the oxygen cascade, of environmental and patient factors and how they may exacerbate the natural fall in oxygen partial pressure? Ask yourself these questions and, if you have a patient who is hypoxaemic, look to the oxygen cascade to give you an answer…
There is an great diagram, and accompanying text, in Ch 10 Nunn’s Applied Respiratory Physiology which will help you with your exploration of this topic. This article from BJA Education also contains some good information.
The most amazing cascades I have seen, even in the pouring rain, – Plitvice Lakes National Park, Croatia….
BT_PO 1.23 Describe the oxygen cascade
Increasing alveolar ventilation will generally increase PAO2 TRUE/FALSE
The effect of a low inspired oxygen concentration can be offset by increased alveolar ventilation TRUE/FALSE
Hypoxaemia caused by increased shunt can be overcome by increasing FiO2 TRUE/FALSE
A sudden reduction in cardiac output will cause an immediate decrease in PAO2 TRUE/FALSE
Diffusion capacity limits oxygen uptake at the the pulmonary capillary in the healthy subject at rest TRUE/FALSE