Question

1. What is the total pressure inside the lungs when air is not moving into or out of the lungs?

2. By how much does the pressure inside the lungs change during 1 entire quiet breath.

3. How does intrapleural pressure compare to intrapulmonary pressure, and why is this difference physiologically important/

Answer 1

1. The total pressure inside the lung when air is not equal will be the same as that of the atmospheric pressure which is 760 mm/Hg'

2. During one cycle of quiet breath or quiet inspiration, there is a pressure difference of 1mmHg. It is due to this pressure difference that air from atmospheric pressure which is higher goes inside the lung where the pressure is lower by 1 mmHg until the pressure inside the lung reaches the same level as that of the atmosphere.

3. Intrapleural pressure is the subatmospheric pressure that develops within the lung pleura due to lung expansion and the simultaneous expansion of the chest wall in the opposite direction. The main difference between the two is that intrapulmonary pressure is the pressure which is exerted by gases that are found inside the alveoli while intrapleural pressure is the one which is exerted by gases between the parietal and visceral pleura.

There is always a difference by 4mmHg between intrapleural and intrapulmonary pressure. The main reason for the same is to avoid lung from collapsing.