Flashcards in Resp - Respiratory Mechanics Deck (65):
1
muscles of inspiration
diaphragm (75%)
external intercostals (25%)
2
accessory inspiration muscles
scalenes (raise rib 1/2)
sternocleidomastoid (raise sternum)
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muscles of expiration (active)
abdominal wall
internal intercostals
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causes for difficulty inspiring
scar tissue
reduced surfactant
mucous
fluid
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causes for difficulty expiring
emphysema
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point where laminar --> turbulent
reynolds # > 2000
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conditions where turbulence likely occurs
velocity high
radius high
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Reynold's number
Re = 2rvd/n
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Ohm's law (airflow)
F = delta P/R
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Poiseuille's law
R = 8L(viscocity)/pi(radius^4)
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Poiseulle's law take away
smaller the airway, greater the R (reduce r by 50% increase R x 16)
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site of most airway R (+why)
medium sized bronchi
smaller than large (up R) and in series rather than parallel (smaller ones in parallel)
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factors increasing resistance
turbulent flow
small radius
lung volume decreasing
bronchial SM contraction
gas density elevated (SCUBA)
forced expiration
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causes of bronchoconstriction
allergy
mucous, airway collapse
PNS during relaxed state (Ach on muscarinic)
low CO2
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causes of bronchodilation
SNS
*Epi (beta-2)
*CO2 up
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forced exhalation
PA drives air out
PA = Pip + P elastic recoil
further from alveoli, less recoil
exhaling air hits R, loses P
EPP
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equal pressure point
when Pairway = Pip
if Pip > Pairway --> collapse
(EPP @ cartilage for healthy people)
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emphysema and forced expiration
alveoli have lost elastic recoil
PA is lower, EPP happens closer to alveoli, compression of airway
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chronic obstructive pulmonary disease (diseases)
asthma
chronic bronchitis
emphysema
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emphysema mech
1. irritation --> many macs, release trypsin
usually alveoli release antitrypsin (but too many macs to fight)
2. breakdown of alveolar walls
3. down recoil, collapse smaller airways
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pulmonary function tests
spirometry
lung vol measurement
diffusion capacity for CO
arterial blood gases
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tidal volume (TV)
V in or out in quiet resp
~500 ml
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inspiratory reserve volume (IRV)
extra V can be inspired after quiet inspiration
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expiratory reserve volume (ERV)
extra V can be expired after quiet expiration
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inspiratory capacity (IC)
max V in after quiet expiration (TV + IRV)
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vital capacity (VC)
max V in after max expiration (IRV + TV + ERV)
~ 4800 ml
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residual volume (RV)
min air remaining in lungs after max expiration
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functional residual capacity (FRC)
V in lungs after quiet expiration (ERV + RV)
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total lung capacity (TLC)
max V lungs can hold (VC + RV) ~6000 ml
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abnormal spirometry results (obstructive)
can't get air out
RV up
up RV, FRC, TLC
--> slow flow, hyperinflation, down recoil
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abnormal spirometry results (restricted)
cant get air in
TLC down
down VC, RV, FRC, VT
--> up recoil, down V
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spirogram measurements
FVC: (V forcibly blown out after full breath)
FEV1: V forced out in 1 second
FEV1/FVC: proportion
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normal FVC
80%
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abnormal spirogram (obstructive)
FEV1 down (a lot)
FVC down
FEV1/FVC down (42%)
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abnormal spirogram (restrictive)
FEV1 down
FVC down
FEV1/FVC normal or higher
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flow volume loop action
1. inhale to TLC
2. exhale to RV as forcefully and quickly as possible
3. forcefully inspire to TLC
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flow volume loop: forced expiration
compression of airways from Pip up --> high flow then slow down
early = pt dependent
late = pt independent
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flow volume loop: forced inspiration
muscle force down as V up
lung recoil up as V up
airway R down as V up
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abnormal flow volume loop (obstructive)
scooped
peak is lower but quick
slow expiration flow
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abnormal flow volume loop (restrictive)
witch's hat
TLC, FVC is lower
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Diffusion capacity action
1. exhale to RV
2. inhale gas (w/ small CO) to TLC
3. hold breath 10 s
4. measure exhaled gas for CO
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diffusion capacity (obstructive)
hyperinflation and DLCO down --> emphysema
hyperinflation and DLCO normal --> asthma
normal lung volume and DLCO normal -->. chronic bronchitis
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DLCO results
DLCO down in any condition affecting alveolar surface area
(lung resection, emphysema)
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diffusion capacity (restrictive)
low RV and low DLCO --> scarring diseases
normal (or high) RV and normal DLCO = neuromuscular diseases, kyphosis, scoliosis
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lung compliance
delta V/delta P
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things that affect compliance
apex vs base
inspiration vs expiration (hysteresis)
disease
amount of CT
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compliance (regional)
compliance greatest at base
gravity pulls on alveoli in apex, makes them more expanded
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compliance (hysteresis)
PV curve diff for inspiration and expiration (not linear)
scoop for inspire, bump for expire
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compliance (disease)
low compliance: stiff - pulmonary fibrosis - large transmural P needed to expand
high compliance: low recoil - emphysema
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elastic recoil relations
directly related to stiffness (low compliance)
inversely related to distensibility (high compliance)
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things affecting elastic recoil
elastin/collagen
*alveolar surface tension (2/3)
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surface tension actions
increases recoil
decreases compliance
responsible for diffs in inspiration/expiration curves
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surface tension relative to size
smaller alveoli more likely to collapse than larger
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LaPlace's Law
P = 2T/r
T = surface tension
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DPPC
dipalmitoyl phosphatidylchloline
hydrophilic head (go in fluid)
hydrophobic tail (go in air)
attenuate cohesion (act as detergent)
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surfactant and alveoli size
most effective when DPPC close together -->
small alveoli have lower ST
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surfactant fxns
1. lower surface tension (increase compliance)
2. stabilize alveoli
3. keep alveoli dry (avoid edema)
58
how surfactant keeps alveoli dry
ST usually lowers interstitial hydrostatic P (pulls fluid in)
surfactant reduces this
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neonatal resp distress syndrome mech
abnormally low production of surfactant
up ST
collapse alveoli (atelectasis)
hypoxemia
60
neonatal resp distress syndrome Sx
cyanosis
pronounced hysteresis
high inflation P to ventilate
pulmonary edema
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alveoli stabilizing factors
elastin/collagen (against overdistension)
surfactant
interdependence (tethering effect)
transmural pressure gradient
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forces promoting alveolar collapse
elasticity (elastin)
alveolar surface tension
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forces keeping alveoli open
transmural P gradient
pulmonary surfactant
alveolar interdependence
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chest volume equilibrium
equilibrium @ ~70% TLC
< 70: recoil force out
> 70: recoil force in
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