lung volumes and capacities, pressures and forces in the chest

164 terms by troxelh 

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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

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