Lung Mechanics

Question 1

What does the functional residual capacity allow?

Answer 1

Ensure the gas exchange at the end of expiration and inspiration

Question 2

What means if physiologic dead space is greater than anatomic dead space?

Answer 2

Presence of alveolar dead space

*somewhere in lung alveoli are ventilated but not perfused

Question 3

What happen to the alveolar ventilation if you increase depth of breathing?

Answer 3

Equal Increase total and alveolar ventilation

Question 4

What happen to the alveolar ventilation if you increase the rate of breathing?

Answer 4

Increase total ventilation>alveolar ventilation

*⬆️ ventilation of dead space and alveoli

Question 5

How is the alveolar pressure at expiration and inspiration?

Answer 5

• inspiration (-)

- expiration (+)

Question 6

What principle explains that a change in intrapleural pressure alters the lung volume and lead in alveolar pressure change too?

Answer 6

Boyle’s law

Question 7

Effect on the left heart of the inspiration

Answer 7

⬇️ left cardiac output ▶️ ⬇️ MAP (mainly systolic)

Question 8

Why does the valsalva maneuver reduce the venous return?

Answer 8

Forced expiration with closed glottis ▶️ positive IPP ▶️ compress great veins

Question 9

Which are the downside of ventilation with PEEP?

Answer 9

• ⬇️ venous return
• ⬇️ cardiac output
• tension pneumothorax

Question 10

Most important component for lung recoil, what law determines the pressure inside alveoli?

Answer 10

• surface tension forces

- LaPlace law: relation between surface tension and pressure inside bubble

Question 11

Why is the effectiveness of the surfactant reduced in ARDS?

Answer 11

Protein seepage into the alveoli