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164 terms

lung volumes and capacities, pressures and forces in the chest

STUDY
PLAY
the lung volume "normal" vary with what?
sex, height, age
what is the volume of air inhaled or exhaled with normal breathing?
tidal volume (TV or Vt)
what is the normal for tidal volume?
500ml
what is the smallest volume?
tidal volume
what is the volume of air that can be inhaled with maximal effort from the tidal end-inspiratory level?
inspiratory reserve volume (IRV)
what is the normal for the inspiratory reserve volume?
3L or 3,000ml
what is the largest volume?
inspiratory reserve volume
what is the volume of air that can be exhaled with maximal effort from a rest tidal end-expiratory level?
expiratory residual volume (ERV)
what is the normal for the expiratory residual volume?
1.1L or 1100ml
what volume is not directly accessible to be measure with spirometer?
residual volume (RV)
what is the amount of air that remains in the lungs after a maximal effort exhalation?
residual volume (RV)
what prevents total lung deflation?
the rigidity of the rib cage and thorax
how can you measure residual volume?
with He dilution, N2 washout, or body plethysmography (body box) with boyle's law
what is the normal residual volume?
1.2L
know chart on page 50 figure 3-6 in Beachey
...
each lung capacity is made up of at least ___ lung volumes?
2
how many lung capacities are there?
4
what are the 4 lung capacities?
...
what are the lung volumes?
...
what is the amount of air in the lungs after a maximal-effort inspiration?
total lung capacity (TLC)
total lung capacity is the sum of what?
all 4 lung volumes
what is the normal for total lung capacity?
about 5.8L or 5,800ml
what is the abbvr for vital capacity?
VC or FVC
what is the maximum amount of air that can be exhaled after a maximal-effort inspiration?
vital capacity
vital capacity is the sum of what?
IRV+TV+ERV
what is the maximal limits of a single breath, from deepest inhalation to blasting it all out as long and hard as possible?
vital capacity
what is the normal vital capacity?
4.6L
what is the amount of air that can be inhaled with maximal effort from a resting tidal volume end-expiration level?
inspiratory capacity (IC)
inspiratory capacity is the sum of what?
TV and IRV
what is the normal inspiratory capacity?
about 3500ml
the inspiratory capacity can be reduced by factors that affect ______ _________, such as emphysema?
elastic recoil
what is the amount of air remaining in the lungs at the end of a normal tidal exhalation, with no accessory muscle use?
functional residual capacity (FRC)
the functional residual capacity is the sum of what?
ERV and RV
what is the smallest capacity?
functional residual capacity
what is the normal for functional residual capacity?
about 2300ml
what is the resting level capacity?
functional residual capacity
what is the balance point of lung's elastic recoil inward and outward expansion of the chest wall?
functional residual capacity
the functional residual capacity contains about 40% of _______ is contained here?
TLC
normally, there is a _______ pressure maintained in the pleural space at all times?
negative
what is the average cwp of the pleural space pressure?
-3 to -5 cwp below atmospheric pressure at end exhalation
the pleural space is more ______ at the apex due to gravity?
negative
due to the elastic recoil of the lungs, the lungs have a natural tendency to want to do what?
collapse inward
due to the elastic recoil of the lungs, the ribs and chest wall want to do what?
expand
due to the elastic recoil of the lungs, and the natural tendencies of the lungs, ribs, and chest, this creates what?
an equilibrium in forces
there are ___ types of airway pressure gradients involved in the mechanics of breathing?
3
what is caused by the expansion and contraction of the thorax?
airway pressure gradients
what are the airway pressure gradients?
trans-airway (trans-respiratory)
trans-pulmonary
trans-thoracic
gas always follows gradients from ________ to __________ low pressure, driving pressure?
high
low
what is the difference between two points?
driving points
pressure is commonly expressed in _____?
cwp (centimeters of water pressure)
although pressure is commonly expressed in cwp, sometimes it is expressed relative to the atmospheric pressure, where 760mmHg is changed to ___?
0
what is the abbrv of trans-airway pressure/trans-respiratory pressure?
Prs
mouth pressure, at opening of the airway, is labeled as _____, or ______?
Pao
Pbs (body surface)
unless + or - pressure is applied to the airway, Pao = ___ (atmospheric)
0
what is the difference between pressure at the mouth (body surface) and alveolar pressure (PA)?
Prs
what is the abbrv of alveolar pressure?
PA
Prs = ____________?
PA - Pao(or Pbs)
Prs is across the entire ______________________?
respiratory system
Prs pressur gradient is what causes gas flow into and out of the ________?
alveoli
what is the abbrv of trans-pulmonary pressure?
PL
what is the pressure gradient between the PA and Ppl?
PL
what is the abbv for pleural pressure?
Ppl
what is the gradient that maintains alveolar inflation; a distending pressure?
PL
changes in PL results in corresponding changes in _____________?
alveolar volume
PL is equal to (balances out) the _______ ______ forces of the lungs when airflow is absent?
elastic recoil
what is the abbv for trans-thoracic pressure?
Pw
Pw = _____________?
Ppl - Pbs
what balances the outward chest wall recoil forces when there is no airflow?
Pw
what is the difference in pressure between the pleural space and the body surface; pressure across chest wall?
Pw
what is the total pressure necessary to expand or contact lungs and chest wall together?
Pw
what is another way of looking at Prs?
Pw
know pictures on the slides
especially slide 35
when there is no gradient, is there airflow?
no
Pao (Pbs) are atmospheric during _________ _____________?
normal breathing
no airflow exists at the end of inspiration or at the end of exhalation because _____________?
PA=Pao
in normal breathing, Prs changes only when the PA changes because Pao remains at ___ (atmospheric)?
0
what disrupts the balance between recoil forces of lungs and outward recoil forces of the chest wall?
inspiration
when muscles of inspiration contract, thoracic volume ____________ and pressure in the cavity ____________ (boyle's law)?
increases
decreases
the change of Prs causes the PL gradient to increase, ______ the alveoli to open up?
pulling
the change of Prs causes the ____ to fall to less than Pao at the mouth?
PA
what establishes a pressure gradient (Prs) and air flows into the lungs?
when PA falls to less than Pao at the mouth
air flow stops when PA ________________________?
rises to = Pao
when airflow stops (when PA rises to = Pao); ______________________ gradient is the greatest, and volume is highest (500ml)?
PL (PA-Ppl)
when breathing muscles relax, what happens?
exhalation starts
when breathing muscles relax, thoracic cavity does what?
passively shrinks due to lung recoil
when exhalation starts, ____ rises (becomes more negative)?
Ppl
when Ppl rises, it decreases what?
the difference between it and PA
after Ppl rises, PA then rises above ___ as alveoli shrink, causing what?
Pao
gas to flow out of lungs
during inhalation, the diaphragm descends, causing what to increase?
thoracic volume
when the diaphragm descends, causing thoracic volume to increase, in turn causes what to happen?
intra-pleural and intra-alveolar to both decrease (boyle's law)
inhalation stops when _________?
PA=Pao
exhalation is _______, diaphragm ___________ and goes _____; causing drop in ______ volume, and increase in ___ and ___?
passive
relaxes
up
thorax
PA
Ppl
the gradient during exhalation, causes what?
flow out of the lungs
Beachey 46,47,48
...
really deep breaths can drop normal intrapleural pressure to what?
-50cwp
forced exhalation can increase normal intrapleural pressure to what?
100cwp
mechanical ventilation uses _______ pressure to inflate the lungs?
positive
pleural space pressure is always ________ during spontaneous ventilation, only changes to more or less __________?
negative
negative
pleural space pressure changes with ________ pressure breaths from machines, it can become ___ or even ________?
positive
0
positive
static means what?
no air flow state
retractive forces-- there are 2 _______ _____ that want to collapse the lungs?
static forces
what are the 2 static forces that want to collapse the lungs?
surface tension of alveoli
elastic properties of lungs (inward recoil)
what is the tendency of an object to return to its original shape after being stretched?
elasticity
what is the natural ability of matter to respond to a force, and then return back to original shape once force is removed?
elastance
what is the change in pressure divided by the change in volume?
elastance
elastic resistance is always present during what?
air flow and static (no flow) states
elastic resistance includes what?
elastic recoil properties of lungs and the alveolar surface tension present
during elastic resistance-- retractive forces and elastance want to do what as much as possible and must be overcome to start inhalation?
keep the lung collapsed
what resistance is only present during airflow?
nonelastic resistance
what cause nonelastic resistance?
by things that produce friction during airflow (muscle, cartilage, fat, blood vessels, airways, secretions)
what is another way of look at the forces opposing lung inflation is what?
compliance
what is a measure of the forces opposing lung inflation?
compliance
what is the distensibility of the lungs?
compliance
what is the equation for compliance?
change in volume / change in pressure
the more compliant the lung is, the more ________ or ________ _________ it is?
floppy
easily stretched
the more compliant the lung is, means there is a ________ volume change for a ______ change in pressure applied
large
small
emphysema lungs are complaint or noncompliant?
noncompliant
a disease associated with the less compliant the lung, the stiffer it is and harder to inflate?
ARDS
as compliance increases, the elastance _________ (airtrapping)?
decreases
what are two types of compliance measurements?
Cstat and Cdyn
static compliance (Cstat) is used when?
there is no airflow
what is it called when you place a pause or hold on an inspired breath from the ventilator to stop gas flow, and then record a pressure measurement?
plateu pressure (Pplat)
Cst = what?
change in V / Pplat
in the Cst formula, the change in V can be in either ___ or ____?
ml or L (most commonly in L)
dynamic compliance (Cdyn) is measure during what?
gas flow conditions
what does PIP stand for?
peak airway pressure or peak inspiratory pressure
what is the equation for Cdyn?
change in V / PIP
what pressure is used to find Cdyn?
PIP
what pressure is used to find Cstat?
Pplat
if pt is on PEEP, what must you do?
subtract that value from the pressure before solving the reset of the equation for both compliance types
emphysema does what with elastic recoil fibers in the lungs? and what does that mean?
destroys
they have a higher compliance but low elastance
are emphysema lungs floppy or stiff? how do they inflate? and how do they recoil?
floppy
easily inflate
do not recoil well
ARDS, atelectasis, fibrosis, and pulmonary edema cause _________ compliance?
decreased
decreased compliance means _________ lungs, ______ volume changes for ________ pressure changes?
stiff
small
large
increased compliance means ________ volumes for ___________ changes in pressure?
large
small
what is the difference between Pplt and PIP?
the energy required
are fluids easier or harder to inflate with air rather than fluid?
harder
gas-fluid interface in the alveoli creates what?
surface tension
surface tension must be overcome to complete what?
inflate the lungs
surface tension in liquids is due to what?
attraction that the molecules have for each other
how is surface tension created?
at the surface, molecules below and adjacent are attracted=the liquid wants to contract
what does the recoil pressure in the air-filled lungs reflect?
the retractile forces of the elastic fibers, plus surface tension of the alveoli
surface tension makes up over 1/2 of what?
elastic recoil pressure
law of Laplace is a physics law that states what?
the tension on the wall of a sphere is the product of the pressure times the radius of the chamber
if there is just one liquid/gas interface, we can set up a equation for ________ ________?
Laplace's law
what is the equation for Laplace's law?
P=2T/r
P stands for what in laplaces law?
distending pressure
what is the unit for P in laplaces law?
dynes/cm2
what does T stand for in laplaces law?
surface tension
what is the unit for T in laplaces law?
dynes/cm2
what does r stand for in laplaces law?
alveolar (bubble radius)
what is the unit for r in laplaces law?
cm
what is the relationships in laplaces law-- r&P? P&T?
indirect
direct
if we have 2 bubbles (alveoli) connected by a common tube (bronchiole), the P would be __________ in the smaller bubble if the surface tension is the same in both?
increased
the smaller bubble is really prone to ________, because it has a higher surface tension, while the bigger bubble needs less P to keep it open?
collapse
because of the connection with the tube, the little bubble would do what?
tend to collapse and empty into the big bubble
what prevents laplace's law from being true in the lungs?
surfactant
what lowers surface tension of smaller alveoli so that the distending pressure to keep all sizes of alveoli open is constant throughout the lungs?
surfactant
what alters surface tension in larger alveoli- it actually increases it if necessary to keep the distending pressure at a constant for all sizes?
surfactant
what has a great effect on the amount of surfactant and its action in the alveoli?
alveolar surface area
as the surface area of the alveoli decreases, the surface tension dramatically decreases because what?
there is more surfactant concentrated together and works harder
big alveoli spread out the surfactant more, so it does not exert its influence as much, which actually will allow what?
the surface tension to increase somewhat thereby balancing things in the system
what are conditions that can cause surfactant deficiency?
ARDS, IRDS, pulmonary edema, pulmonary emboli, pneumonia, excessive pulmonary lavage, near drowning
the conditions that can cause surfactant deficiency cause _____,________ _______, ______ to inflate, and will result in areas of __________?
stiff
noncompliant lungs
hard to inflate
atelectasis