Pulmonary Physiology Topics Flashcards
What is intrapleural pressure?
- Intrathoracic pressure , includes pressure throughout the thorax except in lumens of blood vessels lymphatics or airways
- Another way to think of it is the hydrostatic pressure within the pleural cavity
What is intrapleural pressure (PPL) at rest?
- -5 cm H2O
What happens to PPL during inspiration?
- The volume increases so intrapleural pressure decreases to near -8 cm H2O
What happens to alveolar pressure as the thoracic cavity increases?
- pressure in alveoli decreases
- At rest its 0 cm H20 and at the end of inspiration its -1 cm H20
- This forces air to enter the lungs
What is transpulmonary pressure?
The difference between alveolar pressure and intrapleural pressure
What is alveolar pressure (Palv)?
- pressure within the alveoli exerted by air molecules
What happens to pressure and air movement as the lung volume increases?
- The lung volume increases so the pressure goes down
- Pressure flows from high to low so now air will enter the lungs
What happens to pressure and air movement as lung volume decreases?
- Volume has decreased so pressure will increase
- Air will flow from high pressure to low so now it will move out
What is oxygens pressure in the atmosphere?
150 mm Hg
What is Palv at the end of inspiration?
-1 cm H2O
What is PTP? What should it be at rest?
- Transpulmonary pressure is the pressure difference between aleveolar and pleural pressure
- 5 cm H20 at rest
- If it was 0 the lungs would be collapsed
During inspiration what is happening to Alveolar pressure and intrapleural pressure on the pressure curves?
- Alveolar pressure moves from 0 at rest to -1 cm H2O
- The intrapleural pressure is moving from -5 cm H2O to -8 cm H2O
When the volume of the lungs has achieved Vt, its peak increase, what should the pressure values for Palv and Ppl be?
- Alveolar pressure was at -1 mid inspiration, but now that we have ended inspiration we are back to 0 cm H2O
- Intrapleural pressure has reached its maximum negative value of -8 cm H2O
What is happening to Palv and Ppl during mid expiration?
- Palv is increasing from 0 to 1 cm H2O
- Intrapleural pressure also begins to rise from -8 headed back to the resting -5 cm H2O
What is happening to Palv and Ppl at the end of expiration?
- Palv has decreased to 0
- Ppl has reached its resting value of -5