5.2 Pulmonary Ventilation Flashcards
What is rough atmospheric pressure in mmHg?
~760mmHg
What is “minute ventilation”?
The volume of air breathed into the lungs in one minute
What is ventilation?
The movement of air through the respiratory system
What is vital capacity?
The volume of air that can be expired following a maximal inhalation
What is residual volume?
The volume of air remaining in the lungs after a maximal expiration
What is functional residual capacity?
The amount of air remaining in the lungs after a normal expiration during tidal breathing
What is alveolar ventilation?
The amount of air reaching the alveoli for gas exchange
In which direction does the diaphragm move when it is relaxed/contracted?
Relaxed: Up
Contracted: Down
By what two muscular mechanisms does breathing usually occur? Which is most prominent at rest?
- Diaphragm moves up and down
- Rib cage elevation/depression alters anteroposterior diameter of chest cavity
Diaphragm movement is more prominent at rest
What role do the abdominal muscles play in fast expiration?
They contract to help increase the pressure in the lungs and squeeze air out faster
What is the role of pleural pressure in ventilation?
- Negative pressure relative to atmospheric pressure
- Creates a suction effect
- This way, when the chest wall moves, the lungs also move, helping to create the pressure gradients that enables the cyclic flow of air
What is pressure of air inside the alveoli called?
Alveolar Pressure
How can we calculate compliance?
Change in volume / change in pressure
The more the volume of an object changes for a given change in pressure, the more compliant it is
Broadly, what is transmural pressure?
The pressure inside a hollow object vs outside
What is transpulmonary pressure?
Difference between alveolar pressure and intrapleural pressure
Why would shifting the pressure volume loop of a lung to the left or right alter its elastic recoil?
- Under static conditions, the transmural pressure is equal to the elastic recoil
- If the pressure volume loop shifts laterally, then the pressure acting on the lung at rest has changed, and thus the elastic recoil has been altered
How can elastin-collagen ratio and surface tension influence lung compliance?
- Ratio of elastin to collagen in lung tissue (more elastin, more elastic)
- Surface tension of fluid lining of alveoli (more surface tension, more tendency to collapse inward)
List eight factors that can affect lung compliance
- Age
- Pulmonary blood volume
- Lung volume
- Posture
- Disease
- Bronchial smooth muscle tone
- Surface tension
- Ratio of elastin to collagen
Does surfactant reduce alveolar surface tension by less than or more than 50%
More than 50%
Define surface tension
Tension of the surface film of a liquid caused by the attraction of the particles in the surface layer
List four factors that can cause turbulent air flow
- High flow rate (freeway)
- Branches (intersections)
- Changes in diameter (merging)
- Sharp angles (corners)
What are the 3 major components of respiratory resistance
- Airway resistance (how the air gets to the lungs)
- Lung tissue resistance (when the air is in the lungs)
- Chest wall resistance (the area that the lungs are in)
Effect of vagal innervation on airway resistance of bronchi
Acetlycholine causes contraction of smooth muscle; increases resistance
Describe humoral control of airway resistance
B2 adrenergic receptors initiating bronchodilation in response to adrenaline
There is parasympathetic innervation of the airwarys, enabling bronchoconstriction that increases airway resistance. Is there also a lot of sympathetic innvervation, and how does this influence the activation of B2 receptors?
- There is very little sympathetic innervation
- B2 receptors are activated in response to circulating adrenaline in the bloodstream (hence, largely humoral in nature)
How does parasympathetic innvervation control bronchodilation? After all, it’s responsible for bronchoconstriction!
We can mediate parasympathetic innervation, much like the heart
What is work of breathing?
The amount of energy expended to inhale and exhale enough to meet the demands of the body.
What is transmural pressure, and why is it important in pulmonary ventilation?
- Pressure difference between the inside and outside of a hollow structure (inside - outside)
- During inspiration, pleural pressure decreases more than alveolar, increased transmural pressure and keeping the alveoli open
- During expiration, pleural pressure increases, decreasing transmural pressure
Simply put, what is transpulmonary pressure?
The transmural pressure of the alveoli
