Respiratory Physiology Lecture 2 Part 12: Pressures Involved in the Movement of Air

Question 1

Pressures Involved in the Movement of Air IN and OUT of the Lungs

Answer 1

During inspiration and expiration air moves in and out of the lungs due to variations of the:

• Intrapleural pressure (P_IP)
• Alveolar pressure (P_ALV)
• Transpulmonary pressure (P_TP)

Question 2

P_IP

Answer 2

Intrapleural Pressure

Question 3

Intrapleural Pressure P_IP

Answer 3

pressure in the pleural cavity → static property

• Acts as a relative vacuum therefore negative value that maintains inflation
• Fluctuates with breathing but it is always subatmospheric due to the opposing directions of the elastic recoil of lungs and thoracic cage

Question 4

What happens if the P_IP equals P_ALV?

Answer 4

lungs would collapse

Question 5

P_ALV

Answer 5

Alveolar pressure

Question 6

Alveolar pressure

Answer 6

P_ALV → dynamic property

Pressure of the air inside the alveoli

Question 7

Which pressure is directly involved in producing air flow

Answer 7

P_ALV is a dynamic element, directly involved in producing air flow

Question 8

What does P_ALV - P_ATM govern?

Answer 8

P_ALV - P_ATM governs the gas exchange between the lungs and the atmosphere

F = ΔP/R

Question 9

When are pressures of lung equal to atmosphere?

Answer 9

When the glottis is open and no air flows into or out of the lungs, the pressures in all parts of the respiratory tree, including the alveoli (P_ALV), are equal to atmospheric pressure (P_ATM)

Question 10

P_TP

Answer 10

Transpulmonary Pressure

Question 11

Transpulmonary Pressure

Answer 11

Static parameter and Is the force responsible for keeping the alveoli open, expressed as the pressure gradient across the alveolar wall

Question 12

What does P_TP determine?

Answer 12

lung volume V_L

Question 13

P_TP = ??

Answer 13

P_TP = P_ALV - P_IP

• P_ALV should be always > P_IP (P_TP > 0) in order to maintain the lungs expanded in the thorax
• double negative since P_IP is already negative so becomes positive in physiological conditions

Question 14

Pathway of inspiration

Answer 14

Question 15

How do pressure change during inspiration?

Answer 15

• pleural pressure becomes more negative/ sub atmospheric
• transpulmonary pressure increases slightly
• alveolar pressure decreases than increase
• lung volume increases

Question 16

Pressures at the end of inspiration

Answer 16

• lowest negative value of pleural pressure
• maximum value for transpulmonary pressure
• maximum value for lung volume
• value of 0 for alveolar pressure

Question 17

Pathway of expiration

Answer 17