Mechanics

Question 1

What is normal residual volume?

Answer 1

1-2 L

female 1000 mL, male 1200 mL

Question 2

What is normal functional residual capacity?

Answer 2

2-3 L

female 1800 mL mL, male 2400

Question 3

What is normal total lung capacity?

Answer 3

4-6 L

female 4200 mL, male 6000 mL

Question 4

What is normal vital capacity?

Answer 4

female 3200 mL, male 4800 mL

Question 5

What lung volumes change as age?

Answer 5

increase RV and FRC

Question 6

What is transpulmonary pressure?

Answer 6

pressure acting to inflate the lungs

Ptp = PA-Pip

alveolar pressure - intrapleural pressure

across lungs. remember always inside - outside for transmural pressures.

Question 7

What is transthoracic pressure?

Answer 7

force acting on the thoracic wall

Ptt = Pip - PB

intrapleural pressure - barometric/atmospheric pressure

across chest wall. remember always inside - outside for transmural pressures.

Question 8

What is transrespiratory pressure?

Answer 8

potential pressure gradient for flow into or out of the alveoli

Ptr = PA - PB

alveolar pressure - barometric/atmospheric pressure

remember always inside - outside for transmural pressures.

Question 9

What is the composition of surfactant and where is it produced?

Answer 9

30% protein, 70% phospholipid
dipalmitoyl phosphatidylcholine

Produced by type II alveolar epithelial cells (pneumocytes), activated at about week 30 of gestation

Question 10

Why is surfactant important?

Answer 10

reduces surface tension, which

1. reduces work of breathing (increases lung compliance)
2. stabilizes alveoli (reduced tendency for collapse)
3. causes surface tension to vary with surface area (hysteresis)