Dynamics: Resistance to Air Flow Flashcards
airway caliber changes during
- the breathing cycle
resistance is dependent upon
- radius of airway
- airflow pattern
is resistance constant?
- no
what is airflow pattern determined by
- flow rates
describe laminar flow
- parabolic flow pattern
- center moving faster than near tube walls
pressure drop in laminar flow
- directly proportional to flow rate
describe turbulent flow
- vortices and eddies that increase reaction of fluid with tube wall
- consumes energy
pressure drop in turbulent flow
- proportional to square of flow rate
describe transitional flow
- intermediate state with elements of both laminar and turbulent flow
- eddies present at constrictions or branch points
flow if pressure difference doubled in turbulent flow
- flow will be less than doubled
- it will be the square route of the doubled pressure difference
where in the lungs do we find turbulent airflow
- trachea
- maintstem bronchi
- large diameter structures
where in the lungs do we find transitional airflow
- most of bronchial tree
where in the lungs do we find laminar airflow
- small airways like the normal bronchioles
the pressure difference driving airflow is highest where (in regards to type of flow)
and lowest where
- where flow is turbulent
- lowest where flow is laminar
resistance compared to radius in a tube under laminar flow conditions
- resistance inversely proportional to 4th power of the radius
relationship of flow to tube length
- inverse
relationship of resistance to tube length
- directly proportional
resistance to flow is highly dependent on
- airway generation
the exponential increase in airway number and cross sectional area results in
- decrease in aggregate airway resistance
the highest resistance in the lung is present in
- segmental bronchi
during the final stages of gas exchange in the respiratory zone, gas molecule move more by
- diffusion than bulk flow
why are small airways considered the “silent zone”
- contribute minimally to lung resistance
- disease in these areas must become well advanced before it is easily detected
airway caliber and resistance during inspiration
- airway caliber increases
- resistance drops
airway caliber and resistance during expiration
- airway caliber decreases
- resistance increases
where is total lung capacity located on the flow-volume loop?
- left most point
where is residual volume located on the flow-volume loop?
- right most point
at the beginning of expiration, airflow out of the lung is ________ upon the force of expiration
- dependent
after a certain amount of time of expiration, airflow out of the lung is __________ upon the force of expiration
- independent
effort independent phase of forced expiration due to
- dynamic compression of non-cartilaginous airways at lower lung volumes when airway radius is smaller and resistance is greater
flow during inspiration on the flow-volume loop is
- symmetrical
maximal inspiratory flow develops where on the flow-volume loop
- halfway between RV and TLC
FRC represents
- the point where the outward recoil of the chest counterbalances the elastic recoil of the lung
the net result of increased airway resistance is that
- pressure drop within airway from alveolus towards mouth becomes much steeper
equal pressure point on effort dependent expiration
- located inside larger cartilaginous airways
equal pressure point on effort independent expiration
- lofted in non-cartilaginous collapsable airways
when pressure inside the floppy, noncartilaginous airway becomes lower than pressure in surrounding lung what happens
- choke points develop that collapse the airway
airflow that is effort independent is driven mainly by
- elastic recoil of the lung
what is the equal pressure point
- the point where pressure inside the airway is equal to pressure in the lung tissue
from the equal pressure point towards the mouth as pressure inside the airways continues to drop
- there is now a negative transmural pressure that tries to collapse the airway
why do the non-cartilaginous airways not totally collapse during effort independent phase of forced expiration
- the walls of alveoli that diminish help hold alveolar ducts and small airways open
- alveolar interdependence
coping strategies in obstructive lung disease
- exhale slowly
- breathe at high lung volumes
- create a back pressure via pursed lips
why do people with obstructive lung disease exhale slowly
- lower pleural pressures
- minimize tendency for small airway collapse
why do people with obstructive lung disease breathe at high lung volumes
- increases airway diameter
- lowers resistance
why do people with obstructive lung disease purse the lips
- build up back pressure to hold small airways open
_____ are lower in both obstructive and restrictive lung disease
- peak flows
obstructive flow volume curves have a ________ appearance
- scooped out
why do obstructive flow volume curves have a scooped out appearance
- airways are dynamically compressed earlier in expiration and at higher lung volumes
what is FEV1
- volume of air expired in first second of max expiration
normal value of FEV1 as a percent of forced vital capacity
- > 80%
FEF25-75% represents
- flow during middle half of expiration
- airflows through small airways
- effort independent phase
FEV1 in patients with obstructive disease
- low
FEV1/FVC in patients with obstructive disease
- low
FEV! in patients with restrictive disease
- low
FEV1/FVC in patients with restrictive disease
- super normal
super normal values of FEV1/FVC in conjunction with lower FVC indicate
- reduced lung compliance
- lung is stiffer which makes it harder to fill but easier to empty
spirometry adjusted for
- age
- race
- height
- sex
peak flow
how it is measured
- how fast air is coming in or out
- measured in liters/second
