Respiratory Physiology - Lung Volumes

Question 1

Tidal volume (TV)?

Answer 1

1. Volume inspired or expired with each breath at rest
2. 500ml in males,
3. 350ml in females

Question 2

Inspiratory reserve volume (IRV) ?

Answer 2

1. 2.3L
2. Maximum volume of air that can be inspired at the end of a normal tidal inspiration
3. Inspiratory capacity = TV + IRV

Question 3

Expiratory reserve volume (ERV) ?

Answer 3

1. 750ml
2. Maximum volume of air that can be expired at the end of a normal tidal expiration

Question 4

Residual volume (RV) ?

Answer 4

1. 1.2L
2. Volume of air remaining after maximal expiration
3. Increases with age
4. RV = FRC - ERV

Question 5

Vital capacity (VC) ?

Answer 5

1. 5L
2. Maximum volume of air that can be expired after a maximal inspiration
3. 4,500ml in males, 3,500 mls in females
4. decreases with age
5. VC = inspiratory capacity + ERV

Question 6

Total lung capacity (TLC) ?

Answer 6

• The sum of the vital capacity + residual volume

Question 7

Physiological dead space (VD)?

Answer 7

1. VD = tidal volume * (PaCO2 - PeCO2) / PaCO2
2. Where PeCO2 = expired air CO2

Question 8

How is lung compliance defined?

Answer 8

• Change in lung volume per unit change in airway pressure

Question 9

Causes of INCREASED compliance?

Answer 9

1. Age
2. Emphysema - this is due to loss alveolar walls and associated elastic tissue

Question 10

Causes of DECREASED compliance?

Answer 10

1. Pulmonary oedema
2. Pulmonary fibrosis
3. Pneumonectomy
4. Kyphosis

Question 11

Answer 11