Respiratory 2 Flashcards
What is the alveolar pressure (P alv)?
Pressure in the alveoli
What is pleural pressure? (P ip)
Pressure between parietal and visceral pleura
What is the atmospheric pressure? (P atm)
Pressure exerted by the air surrounding the body
-> it doesn’t change, in order to get air into the body we need to change alveolar and pleural pressure
What is Boyle´s Law?
Inversely relation between volume and pressure
inspire -> we need to decrease the pressure in the lungs -> volume increases : P alv < P atm
f.e. plunger: if the pressure in the lungs and alveoli decreases air is going to be pushed into the airways
expire: P alv > P atm
What is transmural pressure?
transmural = across a wall
= in - out
Transpulmonary = pressure across the lung wall: alv -> intrapleural fluid
-> P alv - P ip
Chest wall = pressure across chest wall: ip -> atmosphere
-> P ip - P atm
Why is the ip pressure negative at rest?
needed to fight against recoiling of the lungs, and keep the lungs inflated when not inflating -> because low pressure increases the volume
Muscles involved in inhalation:
we want to reduce the pressure and increase the volume when we inhale
Diaphragm: moves downward and increases the volume of the thoracic cavity
contraction of external intercostal muscle: elevate ribcage
Sternocleidomastoid muscles raise the sternum: take a real deep breathe
The sequence of events during inhalation:
-The inspiratory muscles contract (diaphragm descends, ribcage rises)
-Thoracic volume increases, Lungs stretch, and intrapulmonary volume increases
-intrapulmonary (P alv) pressure drops to -1mmHg
-air flows down its pressure gradient until intrapulmonary pressure is 0
Sequence during inhalation:
Diaphragm and inspiratory intercostals contract -> Thorax expands -> P ip becomes even more negative (subatmospheric) -> Transpulmonary pressure along lung wall increases -> Lungs expands and thereby P alv decreases -> thereby air flows in
The muscle involved in expiration: if you really want to push out air
contraction of Internal intercostal muscle
Abdominal muscles, external oblique muscle
Diaphragm relaxes
The sequence when we exhale
Inspiratory muscles relax -> Thoracic cavity decreases -> intrapulmonary volume decreases -> intrapulmonary pressure increases (P alv greater than P atm) -> air flows out until pressure difference is equal
The sequence in expiration:
The diaphragm and intercostals relax -> chest wall recoils -> P ip gets less negative, enabling recoiling of lungs -> P alv becomes greater than P atm -> air moves out
What is the transpulmonary pressure at rest?
inside: P alv = 0
outside P ip = -4
0 - (-4) = 4
What is the pressure of the chest wall at rest?
inside: P ip = -4
outside: P atm = 0
-4 - 0 = -4
