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L7B
Mechanics of Breathing
34
Physiology
Professional
02/26/2013

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Term
what are the two types of flow profiles?
Definition
laminar flow and turbulent flow
Term
what is transition flow?
Definition
a mixture of both laminar and turbulent flow -- happens when airways bifurcate
Term
what is the equation for flow?
Definition
flow = pressure gradient/resistance
Term
what is the pressure inside the alveoli at FRC?
Definition
0
Term
when does dynamic inspiration occur?
Definition
from FRC to Vt
Term
what happens during dynamic inspiration?
Definition
a) the diaphragm contracts; b) intrapleural pressure becomes more negative; c) alveolar pressure becomes more negative; d) atmospheric air is sucked into the lung; e) lung volume increases.
Term
what happens during static inspiration?
Definition
a) the diaphragm keeps contracting; b) intrapleural pressure plateaus at low pressure; c) alveolar pressures falls back to zero (patent airways); d) lung volume holds at tidal volume.
Term
what happens during dynamic expiration?
Definition
a) diaphragm contractions decrease and cease; b) intrapleural pressure becomes less negative; c) alveolar pressure becomes positive with respect to the atmosphere; d) lung air is pushed out into the environment; e) lung volume passively decreases back to FRC.
Term
what happens during static expiration?
Definition
lung pressures, flow and volume become flat-line traces until the start of the next breath.
Term
Order of events in cause/effect relationship of the breathing cycle?
Definition
Intrapleural pressure decreases causing alveolar pressure to fall = flow of air into the lungs = volume in lung increases
Term
How are airflow profiles characterized from the trachea to the several branches of each lung lobe?
Definition
turbulent and airway resistances are high
Term
How are airflow profiles characterized in the smaller conducting airways down to the terminal bronchioles?
Definition
laminar and airway resistances are low
Term
How are airflow profiles characterized beyond the terminal bronchioles?
Definition
diffusive and airway resistance is near zero
Term
where is the highest regional airway resistance in the lungs? why?
Definition
generation 4 because the airways are small/short enough and the flow velocity is high enough to produce turbulence during inspiration
Term
Where does half of the total resistance of the airways come from?
Definition
nasal air passageways
Term
Are airway resistances higher or lower at high lung volumes?
Definition
lower because airways are all pulled open which reduces the resistance
Term
Is active expiration from FRC to RV effort dependent or effort independent?
Definition
effort independent
Term
Is active expiration from TLC to FRC effort dependent or effort independent?
Definition
effort dependent
Term
What does effort dependent mean?
Definition
airflow out is proportional to the expiratory muscle effort exerted
Term
Is inspiration effort dependent or effort independent?
Definition
effort dependent
Term
is the lung static or dynamic at end-inspiration?
Definition
static
Term
During dynamic inspiration is the intrapleural pressure positive or negative?
Definition
negative
Term
During dynamic expiration is the intrapleural pressure positive or negative?
Definition
positive
Term
How do you measure FVC using an electronic spirometer system?
Definition
Have the pt slowly inhale to TLC, hold his breath, then explosively exhale to RV
Term
What is the FEV1/FVC ratio?
Definition
Forced expiratory volume in one second divided by forced vital capacity. it is used to diagnose obstructive and restrictive lung diseases.
Term
What is the normal range of values for FEV1/FVC?
Definition
75-90%
Term
What would the FEV1/FVC value be for asthma(obstructive)?
Definition
below 75%
Term
What would the FEV1/FVC value be for pulmonary fibrosis (restrictive)?
Definition
above 90%
Term
What two factors determine the time it takes to fill an alveolus?
Definition
alveolar compliance (C) and alveolar resistance (R)

Time constant (TC) = C x R
Term
What is the "work of breathing"?
Definition
it costs oxygen burning in respiratory muscles to secure oxygen for the entire body
Term
What 2 restrictive diseases decrease the compliance of the lung and increase the work of breathing?
Definition
pulmonary fibrosis
rib cage arthritis
Term
What 2 obstructive diseases increase airway resistance and increase the work of breathing?
Definition
asthma
pneumonia
Term
what type of drugs are given to reduce airway resistance in asthma (which is caused by smooth muscle contraction)
Definition
beta2-adrenergic agonists
Term
How is the driving pressure for expiration calculated?
Definition
alveolar pressure - intrapleural pressure
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