V/Q

Question 1

What is ventilation (V)?

Answer 1

Volume of air reaching the alveoli

Question 2

What is perfusion (Q)?

Answer 2

Volume of blood reaching the alveoli

Question 3

What is a V/Q mismatch?

Answer 3

When the ventilation and perfusion in gas exchange aren’t matched it will significantly impact:
- The oxygenation of the blood
- The removal of CO₂

Question 4

When side lying should the patient’s ‘bad’ lung be faced up or down (in terms of VQ)?

Answer 4

Up (so not lying on the bad side)

Question 5

What is V/Q matching essential for?

Answer 5

Efficient gas exchange

Question 6

What is V/Q affected by?

Answer 6

Body position

Question 7

What does the V/Q ratio assess?

Answer 7

How well matched the PaO2 + PaCO2 variables are

Question 8

What is the normal value for the V/Q ratio?

Answer 8

Ratio = 0.8

(alveolar ventilation is about 4l/min and pulmonary capillary blood flow about 5l/min = 4:5 ratio)

Question 9

What does a V/Q approaching 1 indicate?

Answer 9

Higher probability of optimal oxygenation of blood

Question 10

???

Answer 10

Circulation is obstructed but ventilation is normal

Question 11

What does it mean when the V/Q ratio is less than 1?

Answer 11

An airway is obstructed, and there is no effective ventilation but adequate perfusion

Question 12

What are the considerations for V/Q matching?

Answer 12

• Contraindications
• Underlying cardiopulmonary pathology
• Lines, intubation etc
• BMI
• Skin intergrity
• Nursing care needs
• Haemodynamic instability
• Need for monitoring during after repositioning

Question 13

What is perfusion?

Answer 13

The passage of blood, a blood substitute, or other fluid through the blood vessels or other natural channels in an organ or tissue

Question 14

What is perfusion influenced & affected by?

Answer 14

• Gravity
• The interaction of alveolar, arterial + tissue pressure

Question 15

Does the distribution of perfusion increase up/down the lung?

Answer 15

Down