48: Airflow and Airways Flashcards
EffortDependence/
Independence in Flow Volume Loops
despite effort of exhalation the latter parts of the curves all merge
effort-independent
Flow Volume Loop and Airway Compression
starting slow and then exhaling
forcefully will result in same path decline
Dynamic Compression of Airways
increases resistance to airflow and
effectively limits flow during expiration
no matter how hard you try to exhale the
flow is limited by the collapsed airways
P(tm) +ve
airflow is driven between the
P(a) and P(atm) gradient
P(tm) -ve
airflow is driven between the
P(a) and P(ip) gradient
Equal Pressure Point
Point where transmural pressure is Zero
No positive or negative pressure to hold airway open
Proximal to Equal Pressure Point
Airway pressure less than pleural pressure
Compressive force becomes stronger moving toward mouth
Upper airway compressed
Distal to Equal Pressure Point
Airway pressure more than pleural pressure
Airways are open, flow sustained
High Lung Complaince
lungs have no elastic recoil
Recoil only adds little pressure
Pressure difference not high enough to drive flow through airways
Forced expiration doesn’t happen
Easy for air in, hard for air out
Emphysema or COPD
Low Lung Complaince
Pulmonary fibrosis, lungs have too much recoil
High pressure difference to drive air out
Hard for air in, easy for air out
Lung Volume and Airway Resistance
Expiration:
lung volume declines
resistance to airflow increases
Alveolar diameter change during respiration?
Inspiration: diameter increases, airways open
Expiration: diameter decreases, airways close
Linear distance on resistance
Bigger distance, more resistance b/c of more interaction b/n fluid and walls
Increased pressure difference
Increased driving pressure
Increase in flow
Doubling diameter
Flow = radius^4
16x more flow
Poiseuille’s Law
radius affects resistance
reduced radius, increased resistance
increased radius, decreased resistance
COPD/Asthma
diameter of airway is reduced
increase in airway resistance
hyperventilate/ hyperkapnea to sustain ventilation
Flow Equation
V = ΔP / R
Laminar Flow
maximum amount of flow
Turbulent Flow
form of resistance
work harder to get better flow
Turbulent Resitance
Increase resistance in in upper airways b/c of turbulence, high velocity
Decrease resistance in lower airways b/c of lower velocity and increase in area
Which airways are most affected in asthma?
Mid airways b/c asthma affects upper airways smooth muscles
Which airways are most affected in COPD?
Terminal airways b/c COPD inflammation occurs in alveoli and up respiratory tree
