TLCO

Question 1

VA

Answer 1

Surface area available for gas exchange

Question 2

KCO

Answer 2

rate of transfer of CO

Question 3

Understanding VA

Answer 3

Surface area of the lung available for gas exchange.

VA may be reduced as a function of:
1. Reduced TLC (Total Lung Capacity)
2. Poor gas distribution throughout the lung as a consequence of obstructive lung disease.

Question 4

Normal range and Standardised residuals (SR)

Answer 4

Normal range (±1.64)
Mild (±1.64 – 2.50)
Moderate (±2.5 – 3.5)
Severe (±3.5)

Question 5

Physiological Influences

Answer 5

1. Alveolar expansion. -TLCO decreased by ~5% per 10% decrease in VA
2. Cardiac output.
   - Exercise
   - Pneumonectomy
3. Anaemia.
4. Smoking.- COHb incr. 1% ~ TLCO decr. 1%

Question 6

VA normal / KCO reduced

Answer 6

Alveolar Volume (VA) is normal, indicating lung parenchymal and/or pulmonary vascular dysfunction.

Question 7

VA reduced / KCO normal

Answer 7

Due to loss of alveolar volume rather than lung parenchymal disease or pulmonary vascular disease.

Question 8

VA reduced / KCO reduced

Answer 8

Alveolar Volume (VA) and CO transfer coefficient (KCO) are both reduced due to loss of alveolar volume but also indicating lung parenchymal and/or pulmonary vascular dysfunction.