Resp Exam 2 Shunt/Deadspace VQ Flashcards
VQ describes the ____ of ventilation to ____
Ventilation to perfusion
Does ventilation always equal perfusion?
No
Ventilation without perfusion is
Deadspace
Perfusion without ventilation is
Shunt
Atmospheric O2 and CO2
Atmospheric O2 = 150
Atmospheric CO2 = 0
____ equilibrates with concentration gradient as it perfuses
Blood
Normal VQ unit results in blood with a
PO2 of
CO2 of
Normal VQ
PO2 100
PCO2 40
In a shunt, the VQ is
0
Shunt unit results in blood with a
PO2 of
CO2 of
PO2 40
PCO2 45
(think perfusion w/o ventilation) so PO2 and PCO2 will stay at the numbers of the blood entering
Dead space unit results in blood with a
PO2 of
PCO2 of
PO2 150
PCO2 0
(think ventilation w/o perfusion) so PO2 and PCO2 will stay the same as the environment
In a deadspace unit, the VQ is
Infinity
***Ventilation w/o perfusion
Absolute shunt means
Absence of ventilation
Relative shunt means
Less ventilation than normal
Absolute dead space means
Absence of ventilation
Relative dead space means
Less perfusion than normal
Alveoli at apex are _____ and _____
Underperfused and overventilated
Alveoli at base are ____ and ____
Overperfused and underventilated
Apex VQ ratio is
3.4
*** HIGHER
Base VQ ratio is
0.63
*** LOWER
Deadspace VQ is
> 1
(top of lung)
Shunt VQ is
< 1
(bottom of lung)
When alveoli are underventilated…
Shunt
What helps underventilated alveoli?
HPV
When alveoli are underperfused…
Shunt
What helps underperfused alveoli?
Bronchiolar constriction
Blocked airways lead to ____
Shunt
If you have a blocked airway, you will see a problem with
Oxygenation
Destroyed alveolar walls lead to ____ which leads to ____
Dead space
CO2 retention
Does VQ affect PO2 or CO2 more?
PO2
**BECAUSE CO2 IS SO SOLUBLE
What is the most common cause of hypoxemia?
VQ mismatch
In physiologic deadspace, what exceeds what?
VQ ratio exceeds normal
In physiologic deadspace, is ventilation wasted?
Some of it
Physiologic dead space includes
Anatomical and functional/alveolar
As dead space increases… what also increases?
CO2
WOB
In pulmonary shunt, what is below normal?
VQ ratio
Does all pulmonary capillary blood get oxygenated with a pulmonary shunt?
No
In a true, anatomic shunt… what blood is included?
Venous admixture
Total quantitative shunted blood per minute is called…
Physiologic shunt
As shunt increases… what decreases?
Oxygenation and PO2
