Ventilation and Compliance

Question 1

Tidal volume

Answer 1

Volume usually breathed in/out

- 500ml

Question 2

Expiratory reserve volume

Answer 2

Maximum volume which can. be exhaled after normal inspiration

• 1100ml in males
• 800ml in females

Question 3

Inspiratory reserve volume

Answer 3

Maximum volume which can be inhaled after normal expiration (on top of tidal volume)
- 2000-3000ml

Question 4

Inspiratory capacity

Answer 4

Volume of air that can be inspired following normal expiration (TV + IRV)
- 3500ml

Question 5

Residual volume

Answer 5

Volume of air that cannot be exhaled after maximal expiration
- 1200ml

Question 6

Functional residual capacity

Answer 6

Expiratory reserve volume + residual volume

Question 7

Vital capacity

Answer 7

Maximum volume of air a person can expel after maximal inspiration

• TV + IRV + ERV
• 4800ml (3-5L)

Question 8

Total lung capacity

Answer 8

Vital capacity + residual volume

- 6 (5800ml)

Question 9

FEV1:FVC

Answer 9

Fraction of forced vital capacity expired in 1 second

- Normal: 80% (4L/5L in male)

Question 10

Pulmonary ventilation

Answer 10

Total air movement into/out of the lungs

Question 11

Alveolar ventilation

Answer 11

Volume of fresh air getting to the alveoli per minute

Question 12

Partial pressure

Answer 12

Pressure of a gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multiple by the presence of the whole gaseous mixture

Question 13

Alveolar PO2

Answer 13

• 100 mmHg

- 13.3 kPa

Question 14

Arterial PO2

Answer 14

• 75 mmHg/ 100mmHg

- >10.6 kPa

Question 15

Alveolar PCO2

Answer 15

• 40 mmHg

- 5.3 kPa

Question 16

Arterial PCO2

Answer 16

• 35-45 mmHg/ 40 mmHg

- 4.7-6 kPa

Question 17

kPa to mmHg conversion

Answer 17

1 kPa = 7.5 mmHg

Question 18

Pulmonary surfactant: Production

Answer 18

• Stimulated by thyroid hormones and cortisol between 25-36 weeks gestation
• Type II pneumocytes
• Pathology: IRDS

Question 19

Pulmonary surfactant: Function

Answer 19

• Reduces surface tension on alveolar surface (reducing tendency to collapse)
• Increases lung compliance
• Reduces lung recoil
• Makes breathing work easier
• More effective in small alveoli (higher surfactant concentration)

Question 20

Law of Laplace

Answer 20

P (inward) = 2T (surface tension) / radius of alveoli

Question 21

Lung compliance

Answer 21

Change in volume relative to change in pressure

• Represents stretchability of lung
• High = large increase in lung volume for small decrease in Pip
• Higher at base/back when lying down (gravity)

Question 22

Obstructive lung disease

Answer 22

1. Airway obstruction
2. Increased resistance of air flow (especially on expiration)

Lung compliance = normal
- FEV1/FVC decreased

Question 23

Restrictive lung disease

Answer 23

1. Lung stiffness increases
2. Limits lung expansion

Lung compliance = decreased (lung elasticity increased)
- FEV1/FVC normal or increased

Question 24

Static spirometry

Answer 24

Measures volume exhaled

Question 25

Dynamic spirometry

Answer 25

Measures time taken to exhaled a certain volume