Respiratory 22 Flashcards
What is the ventilation/perfusion (V/Q) ratio?
The balance between the ventilation (bringing O2 in to/removing CO2 from the alveoli) and the perfusion (removing O2 from the alveoli and adding CO2)
What is one of the major factors affecting the alveolar and arterial levels of O2 and CO2?
The ratio between ventilation and perfusion
What is Lung Perfusion?
The amount of blood that passes through the pulmonary capillary system in the lunng
What is Ventilation?
The exchange of air between the atmosphere and the alveoli
How is PO2 and PCO2 affected by ventilation?
The greater the ventilation, the more closely alveolar PO2 and PCO2 approach their respective values in inspired air
How does Perfusion affect the composition of alveolar air?
The greater perfusin, the more closely the composition of local alveolar air approaches the of mixed venous blood so there will be a reduction in PO2 and an increase of PCO2
What will cause the Ventilation to Perfusion ratio (V/Q) to be high?
- An increase of ventilation (V)
* A decrease in perfusion (Q)
Which parts of the lungs have a high V/Q ratio?
Alveolar or Physiologic dead space
In what cases can we see a hugh V/Q ratio?
- Collapsing of lung arteries
- Pleurisy
- Diseases that affect the vasculatory system
What will happen to the V/Q ratio if a pulmonary capillary is occluded and why?
The V/Q ratio will increase because ventilation is still occurring but perfusion is not causing O2 to build up and no gas exchange occurs so there is no CO2 in the alveoli similar to the alveolar air
What is Alveolar Vd (dead volume)?
Regions of lung with high V/Q ratios because they are over ventilated (underperfused) so that fresh air reaching the alveoli can not be taken up the blood
What is the difference between alveolar dead volume and anatomical dead volume?
Anatomical dead volume is the volume of conducting airways that do not participate in gas exchange while alveolar dead volume reflects the conductive zone where gas exchange does not occur because it is not properly perfused
What will causes the V/Q to decrease?
A collapsed alveoli
What occurs in a decreased V/Q?
This is due to no ventilation in the alveoli. Blood will still go to the alveoli but it doesn’t get oxygenated so PO2 will will decrease and PCO2 will increase in the alveoli
What is a shunt?
A portion of the venous blood that doesn’t get oxygenated and goes back to arterial blood resulting in low V/Q
