S2 Ventiliton And Lung Mechanics Flashcards
What is the role of the lungs in tidal (normal) breathing?
Bronchioles dilate, increasing their volume and lowering the pressure inside the lungs below atmospheric, moving air in
What is the role of the chest wall in tidal breathing?
Parietal pleura secretes fluid, the surface tension of which adheres the two pleural layers together.
So when the chest wall expands, the Parietal and visceral Pleura moves with it, moving the lung too
What is the role of the diaphragm in tidal breathing?
Contracts and descends
Define tidal volume
The volume of air that enters and leaves each breath.
Define vital capacity
The biggest breath that can be taken in, from the max inspiration to max expiration, is about 5L.
Define the resting end-expiratory level (FRC)
The volume of air in the lungs at resting expiratory level.
What causes the pressure in the pleural space to become negative?
The balance of elastic forces of the chest wall, favouring outward expansion, and the elasticity and surface tension of the lung, that generates an inward force.
The net effect is that the forces balance each other creating a negative pressure within the intrapleural space relative to atmospheric pressure.
What will happen if the pleural seal is broken eg a pneumothorax
The lung will collapse as surface tension is lost
Describe the muscles involved in quiet breathing
Inhalation: Diaphragm, External Intercostals
Exhalation: None, passive, due to elastic recoil
Describe the muscles involved in forced breathing
Inhalation: SCM, Scalene, Pectoralis major
Exhalation: Internal and Innermost Intercostals, abdominal Muscles
What is lung compliance?
The volume change per unit pressure change.
It is the stretchiness of the lungs .
High Compliance means that the Lungs are Easy to Stretch.
What is the role of surfactant?
Produced by T2 pneumocytes
Surfactant reduces surface tension increasing lung compliance.
It stabilises the lung, preventing small alveoli collapsing into big ones.
What is dead space?
Anatomical dead space is when only part of the tidal volume is available for gas exchange, the rest refills conducting airways from the nostrils to the bronchioles.
Alveolar dead space is where alveoli are ventilated but not perfused.
How do you calculate alveolar ventilation rate?
Alveolar vent (L/min) = (tidal vol – dead space) x resp rate
Is the airway resistance higher in the upper or lower respiratory tract?
Upper
Usually larger tubes have less resistance; however resistance of the small airways is low due to them being connected in parallel.
