Hussain Flashcards
What factors go into air resistance?
Increased resistance: viscosity, length
Decreased resistance: radius
Things that go into whether flow is laminar or turbulent
Reynolds number
Increased turbulence: velocity, large radius, large density
Decreased turbulence: viscosity
As lung volume increases, does airflow resistance increase or decrease?
Decrease - alveoli are tethered to the small airways, I believe the alveolar ducts. So, as the alveoli get larger, they pull on the small airways and make them larger, thus decreasing airway resistance.
What type of airway has the most resistance
Medium sized
What is the equation for change in pressure =
P = flow X resistance
Where is majority of resistance to the inspired air coming from?
80% from the airway (conducting system)
20% from the parenchyma
Pouiesellies Law
Flow is proportional to the increases in pressure as well as increases in radius of the tube to the 4th power.
Equal Pressure Point Hypothesis
If you have forced expiration, the alveolar and intrapleural pressure increase (while keeping transmural pressure the same). Because of this, at some point, the pressure inside the airway will equal the pressure in the intrapleural space. This is called the equal pressure point. Above this, pressure is lower inside than outside and you have a negative transmural pressure. Below this, airways wil begin to collapse if they do not have cartilaginous support. As expiratory force increases, the equal pressure point moves down, where we have no cartilaginous support, and more airways begin to collapse.
Effort dependent vs. effort independent
If you increase intra-pleural pressure more positively, expiratory flow will increase… To a point. The beginning of expiration is effort-dependent, meaning that as you increase expiratory effort, flow will be increased. However, at some point, no matter how hard you try, flow rate will be the same, so we call this effort-independent.
