SF3 Exam 2 V/Q Flashcards
What is an A-a gradient?
PAO2-PaO2
If the A-a gradient is large, what does this indicate?
What is the normal range?
Large indicates disease in the lung.
Up to 15 Is normal
Anything greater than 15 is considered to be disease
How is V/Q different throughout the lung?
Top- high V/Q
Bottom- low V/Q
This is the case for any orientation of the lung. The top always has a higher V/Q
What can a lung transplant make better?
What type of disease will it not help at all?
Helps Fibrosis. More air goes into the healthy lung as opposed to the stiff one.
Does not help emphysema. Air will continue to rush into the emphysematic lung as it is more compliant and the new lung will have the higher profusion. Gas exchange will not be fixed or get better long term
What is the relationship between PACO2 and V/Q?
Inversely proportional.
A high V/Q indicates a low PACO2
What is the relationship of PaO2 to V/Q?
This is a direct relationship.
What would make V/Q equal to infinity?
No blood flow.
The PACO2 would also be 0.
What makes V/Q=0?
Block of air to the lung.
PACO2 would be around 46
What is the best way to reduce hypoxic pulmonary vasoconstriction?
Nitric Oxide @ 20ppm
What does a V/Q mismatch result in?
Hypoxemia
Hypercapnia
High A-a gradient
What compensatory mechanism(s) occurs during V/Q mismatch?
- Local smooth muscles contract to send blood flow elsewhere.
- Hyperventilation resolves hypercapnia, but hypoxia remains
What orientation does the Lung have the highest A-a gradient? What makes the gradient smaller?
Standing straight up is the highest gradient
Laying down reduces the overall gradient
What can you not treat with 100% oxygen?
A shunt increases in PaO2 slightly, but it will not fix the issue.
What can you treat with 100% oxygen?
V/Q mismatch
What does a high V/Q ratio indicate?
Pulmonary embolism
Lung geometry (high V/Q at top)
