4.3 Non respiratory functions lung & shunt

Question 1

What is the fxn of type 2 alveolar cells

Answer 1

Production of surfactant

Stemm cell production type 1 cells

Type 1 are produced from type 2

Type 1 are thin
no signif barrier to gas exch

No ogranelles
dont divide

Lung damage -
2 divide to produce replacement

Question 2

How are alveolar epithelial cells affected by oxygen toxicity

Answer 2

Thin Type 1 - easily damage high levels of oxygen
larger type 2 more resistant

Alveolar epithelium becomes thciker than normal - impariment of gas exchange

Oxygen conc return normal - type 2 prolif to replace 1`

Question 3

What is surfactant

constitituents

Answer 3

Reduces surf tension - air liquid interface alveoli - redution larger in small alveoli

Stored type 2 alv cell - lamellar body
secreted into alveoli

Surfcat composite
Plip 80% - dipalmitoyl phophatdiyl choline

Neutral lipids 10%

Plasma proteins 4 %

Carbs 2%

severeal surfactant protiens 4%

Question 4

What is the chemi feat dipalmitoly phophatdiyl choline - gives surface tension reduction activity

Answer 4

Ampipathic -
Charged Hydrophilic head - choline
hydrophobic tail - two palmitoyl groups

Struct feat - important orinetant of moleculs at air liq interface

Question 5

What are the functions of surfactant

Answer 5

Reduce surface tension alveoli

• reduce effort
• mag dep conc on surf of fluid layer lining

when smaller - surf area smaller - conc surf - interface higher

radially dependent seufrace tension red agent - mag reduction tesnion depened radius aloveli
countract effects pred law lpalace - small alveoli higher pressure than large

improve stability

assist keeping dry
Oppose movement water from interstit to alveolar space
reducing collapse alvoli - reduce hydrostaitc pressure in tissue outside capillary

Question 6

Roles surfactant proteins

Answer 6

4 specific protien found a- d
sp a sp b sp c sp d

sp b sp c - hydrophobic - neccessary spreading phospholipid into a monolayer lining alveoli

Sp a sp d -hydrophilic 
sp a-
faciltate spread sp b - break lamellar body
prevent plasma pro entry into fluid
macophage enhancement
regul8 surfactant turnover

Question 7

Non respiratory fxn lung

Answer 7

1 Blood resevor
2 blood filtration - thrombi removed b4 brain
3 Metabolic
-surfactant
-protein collagen + elastin
-r/o proteases a1at
- metabol vasoactives
4 immunlog - macopahge iga
5 heat reg
6 air flow - facil speech
7 Drugs - rout admin some drugs -

Question 8

Mech as blood resevoir

Vol lying
standing
vol capillary

Answer 8

Increase in PA pressure - increase vol blood lung - increase bentral blood vol
Recuitment - more vessels open
distenion - open bet bigger

Vol 450 lying
standing 250

Vol capillary 80

Question 9

What is central blood volume

Answer 9

Volume blood in heart and lungs

errect 15%
lungs 450. heart 350 = 800

Question 10

What way is pulmonary circ different?

Answer 10

1 Whole of CO - RV
Most blood traverese capillary
lung receives venous efflent whole body - mix ven blood
cap bed filter whole VR - only capillary bed capable of same

Second
Pulmonary circulation reacts low Po2 - constricting - HPV
Redirect blood away poorly vent alveoli
response system opp - vdilates
Perip vdil aim increase o2 supply / blood flow

Higher flow at lower pressure and vascular resistance

Question 11

What is converting enzyme

Answer 11

ACE located pul cap endothel cell
2 fxn

1 Converts Ang I to active ang II - ang convertin enxyme
drugs which inhib ace - useful antihtn

Inactivaing bradkinin - inhib of fxn - lead ace side effect
eg angioed cough

Widely distrib body - lower conc than capillary

Question 12

How are the vasoactives handled by lung

Answer 12

Activate aAng I

Inact Bradykin

Taken up 5HT, PGE2, PGF2, LK

Unaffected AngII pGA ADH, Adrenaline

Question 13

What is the role in heat regulation

Answer 13

Upper resp tract fxn

upper aiwrway warm and humidfy gas to inspire gas to body temp

Obiltory loss of heat by route - latent heat vpa
req for evap water

eheat loss .58kcals per gram water ecap
daily resp insense water loss 400mls heat loss 230 kcal day
12%

Question 14

What are major defency mech protect lung

Answer 14

Physical
1 upper airway filter mech & particle impaction
2 Airway reflex cough sneeze
3 Mucocillary escalator

Cellular mech
Alveolar macrophage
Iga - immun fact

Question 15

Respiratory response to altitude
what is percent o2 air at 5500m
380mmhg where ambient pressure 1/2 sea level

Answer 15

Percent oxygen still 21%

Partial pressure oxygen air less
as ambient pressure is half
ambient po2 is 80 (.21x380) in dry
or 69 in saturated

Question 16

What Po2 would you predict if alveolar vent was same as sea level

Answer 16

PAO2 = Pi - PACO2/r

= .21 (380-47) - 40/.8
= 20mmHg in absence in change of centilation

Question 17

What vent response to asecnt to 5500

Answer 17

Hypoxameia - stim periph chemo rec - ventilation increase signifcantly

Resultts fall PaCo2 - acts central cehemo rec - inhibt chemorec in resp centre - limit vent rise

Action of fall in art Pco2 - d/t local brain ECF [H]
over days - bec equil accross bbb - preogres resotre ecf H to normal

Inhbi to increase in vent progress removed

vent rises marfkedy increase alveolar Po2 - decrease PCo2 - typcall takes secereal days before max response achieved (can inc x5)

Question 18

What else involved acclimiatisation to altitude hypoxia

Answer 18

Increase oxygen uptake

increase tport and delivery

the above 2
increase Hb conc - hypx stim epo - may increase >20

Increase caplarry in muscle to failatte perfusion

Positon ODC alter -
left shift - hypocap
right shift inc 2 3 dpg -

Oxygen loading - decrease combo low alverolar po2 and right shift cyrve

Polycthtme - incr blood viscosity
HPV d/t low alv Po2 - increase PA pressures

Both - increase work / strain rihgt heart

PHTN & RV hypertrophy may occur

CO increase by 20 to 50% on ascent to altitude
as vent and Hb inc - co return normal

people live life altitude - high conc oxidative enzymes - great ability utilise oxygen

increase oxygen utilisation

Question 19

Functions nose

what structural features assist

Answer 19

Pathway for bulk flow gas

smell

conditioning ventilated gas

Minimisation water loss resp tract

Eustachian tube enter nose

Major process condition inspired gas -

Humidification
Warming
removal particulate matter

All - assisted turbulent flow
increase surf area - turbinates

min water loss during expiate
moisture condense during expiration
-would lose 75% daily water intake if turbinates mechansim

warming and humid related - increase in temp increase amt water vapour req fully sat the air

Processes involved removing particulate
filtration:
hair

impaction on muscoa

sedimentation lim nose -
important in trachea and large bronchi

Question 20

How much total airways resistance d/t the nose -

Answer 20

Major contributr and ressitance increase and insp flow rate increase

Mouth function low resistance bypass - short activation time

Resistance slows expiration help main lung vol and prevent atelectasis - phys peep

resistant - internal shape and feautres - favour turbulent flow

Question 21

Functions of rbcs

Answer 21

1 Tport of oxygen

2 co2 tport

3 a b buffer

4 package hb

hb also carry NO - affinity reduc deoxy = release NO periph

Question 22

How are function interrelated

Answer 22

Hb - 3 roles -
Haldane effect of o2 sat of hb on co2 tport

hb carbamino - imporant co2 tport

Bohr effect- pco2 and ph on o2 tport

hb buffer - imporntant co2 tport and ab balance

buffering affect degree sat - hb

carbonic anhydrase inside rcc

Question 23

What are advantage of having Hb locate in RCC

package of hb

Answer 23

Protect fo filt

enverino raise p50 26.6 - allosteric effect 2 3 dpg which phys more advant

avoid icnrease plasma oncotic pressure if hb in solution

assist mainta as stable teatrae - posit coop

main same locn carbonic anyhdrase

return methb - back to hb - methb reduct in rcc cyto

Question 24

Role RCC CO2 tport

Answer 24

Co2 tport in 3 forms in blood70% bic lelavce1 dissolved 2 bic 90% - accounbts 60% av diff co2 content 3 carbamino

RCC import
1 anyhdrase in red cell not plasma
2 Hb forms carbamino compoinds
3 hb buffer H production bic

Bic formed from co2 and water - carbon anhydrase catalyses
Fast

70% bic leaves RCC - hambuger- exchange Cl (cl shif)
Maintain elec neutraility

Hion production reaction
increase H disav - not removed limit bic production ( las mass action)

Addit low ph inhib prod 2 3 dpg
H is buffer by Hb

oxygen unloading facilate process - deoxy is ab tetr buffer than oxy
imidazole grooup 6.8 pka - histdine responsible most buffer

hb large no histidine residue (38) - designed buffer

Carbammino comnpound account 5% CO2 carriage contib 30% av diff co2 content
more imporrartant tport in venous blood -
compound formed combo co2 terminal aminos

Net prod H low pka carbamic acid

Formed with hb nad plasma protein
hb presnet 2x conc pl portein

Question 25

Haldane effect

Answer 25

• increase co2 carry at same pco2 in deoxy v oxy

doexy 3/5 x more carbamino compared to oxy
- account 70% haldane effect

Secon dfacotr - ncrease buffering ability deox- mops H+ formed production bic

More bic formed because of buffering
some dissolved co2 present co2

Question 26

Role RCC in AB meatbolsim

Answer 26

Hb - high contc many histide reside - suiot pka buffer phys ph

doexy better buffer - than oxy

buffer H prod from carb anyhdrse in rcc bic buffer cant buffer itsekf

Question 27

What is role of RCC membrane

Answer 27

Gas tfer - oxy co

tfer bic to plamsa

cl shift

prote hb - glom fil stable

immunolog function rcc naito abo

Question 28

Mechanics breathing

What are the muscle involved in ventilation?

Answer 28

Inspiration is active - d/ tcontract diaphragm
- contract Ex IC also cintrib

Diaphr respo 70% TV - traonctacion msucle causes intrapleeural - more eng - decrease alveolar pressure
gradient for inspiration dfiff alveolar and mouth pressure
Diaphr lower rib c3-c5

External contract ribs move up and forward
buckel hand increase tb diagram pump handle increase AP dap
TV not impair if ext IC paralysed

Question 29

How much does dipahgram desed during tv and vc

Answer 29

TV - 1 cm

VC 10c,

Question 30

What is oxygen cost normal TV at rest

Answer 30

3mls o2 min

1% consump

Question 31

Why do we breath out

How diff exercise

Answer 31

Normal exp - passive
no active contraction - active require energy
energy elastic recoil lungs
during inspiration elastic potentinal energy in lung increase

with expriation - elastic potential energy used gen pressure gradient driving expiration - pull chest wall back to FRC
work expiration powered by inspiratory muscle - intermed store elastic pot energy lungs

exercise
rectas abd
int ext obliq tv and inter itercostal

Question 32

What pressure gradient driving expiration

Answer 32

diff alvoelar press and mouth pressure

Normal TB peak alveolar +1cm

mouth pressure atm - 0 gauge

Question 33

Whats respons for elastic recoil of lung

Answer 33

Factors responsible -
1 Surface tension of thin film of fluid lining alveolus
70%
surfactant - reduces reduction marked smaller size

2 Stretch elastic fibre in lung parenchyma fibres elastin collagent

Question 34

Alveolar Arterial pO2 gradient

What is A a gradient

Answer 34

Num diff alve and art po2

PiO2 - PaO2

Ox tension difference ref to dA-aO2

Question 35

What is ideal alveolar Po2

Answer 35

Ideal alveolar pO2 - Po2 present in alveoli -
No V/Q inequality in lung
+
Lung exchange gas same rate resp exchange ratio as real lung

Calc from alveolar gas eqn

Question 36

What is use of A-a gradient

Answer 36

Index amt v/q mm and shunting

Question 37

What need to know calc Aa

Answer 37

Inspired Oxy blood gas result

pAo2 - alve gas eqn

pao2 measured from blood gas

Question 38

What factors affecting A-a

Normal values

What causes this gradient

Answer 38

VQ mm
Shunt
Diffiusion abnorm

Usually 5mmHg in young fit health

values 15mmHg - breathing room air acceptable

Value - higher in healthy elderly - no disease state

V/Q mm or scatter vq ratio

Shunt - small amount noirmal shunt bornch circ and thebesian vein drain left heart

diffusion
End pulm cap same Po2 alveolus - wall pases
extreme stress - path A-A d.t diffusion prob
-

Question 39

Is Aa same in adults and pead

Answer 39

Neotates higher 30mmhg
increase venous admix shunt v/q scatter

Amount intrapulmonary shunt higerh - unexpaind / fluid alveoli

alveoili low vq common

Frc < CC - gas trapping occurs - normal tv

Art Po2 neonates - lower above but effect o2 delivery offset
Increase affinity Hbf
Increase CO
Increase HB after birth

HbF - 80% hb in neonates

Neoanates higher o2 consump 6mls kg min vs 3-3.5

Question 40

How does v/q MM cause increase a-a grad

Answer 40

Lungs unit at apex - high v/q
end cap blood high Po2
not signif increase from blood - hb alm cmplete sat

Lungs base - lower v/q
conseq end cap blood drain lower Po2 than apex
lower po2 -a/w lower oxygen content as o2 sat of hb sligh decrease

total perfusion of basal units higher - perfusion base lower o2 content contrib more toal flow
lower Pv art Po2 -

SUMMARY
High V/Q apex - not contrib extra oxygen - flat curve
also doesnt contrib much flow

Low v/q base contrib flow at lower Po2
base most imporant effect and causes lowering art PO2 - increase Aa grad

Flow apex - not compenaste lowering - high po2 doesnt contrib compenaste increase oxygen
apical flow small

Question 41

In patients w/ lung disease and icnreased scatter of V/Q rations
do unit high v/q ratios and units low v/q ratio contribute to increased Aa grad

Answer 41

Yes
maginutide contribute lung units to increase Aa can be estimated

Contribution units low Cq - assesd mesaure phys shunt w/ shunt eqn

Cintrib high v/q - assesed measure phs dead space -using bohr

Type analysis - approximation based asusmption lung

Question 42

Increased Aa gradeint - decrease art po2 a/w increase pco2?

Answer 42

No

Increase art pco2 - sense central and perip increase vent
resore art pco2 normal

pco2 only eleveated additional factor impar pco2 feedback control

Reason icnrease alve vent restore pco2 - linear slope co2 dissoc curve

increase vent - decrease co2 content blood - some area lung compensate increase co2 cotnent blood underventilated

different situation oxygen flater upper part oxyhb mean increase cent not add adit oxygen compensate decrease content

Question 43

Hypoxaemia vs hypoxia

Answer 43

Hypoxia - Presence tissue low enough adverse affect on tissue fxn

hypomaemia - abnormally low Po2 in arterial blood

Question 44

Classify hypoxia

Answer 44

Hypoxic hypoxia -
gypoxia d/t low blood po2

Anaemic hypoxia
D.t inadeq tissue delivery oxygen by hb w. anaemia of CO pois

Circ hypxoia
inadeq blood flow to tissue - critical fall in Po2
may affect whole body
certain part - tonrinquet

Histotoxic

Question 45

Why does hypovent cause hypoxaemia

Whats effect art pco2

Answer 45

Hypovent - less o2 deliver to and less co2 removed

rise alverolar pco2 pred pco2 inversel relate to alv vent

Fall alveolar Po2 - det use gas eqn

PAO2 - Pi - PACO2 / R

Eg - alv vent halved - doublin paco2 - inverse relationship

0.21 x 760-47 - 80.8
= 50

Art po2 lower - tissue po2 lower than that

Question 46

Histotoxic hypoxia

Answer 46

Tissue are not able use oxygen normal

cyanide pois
binds inhib mito cytoo x
ox cant react w/ H deliver from ETPch - oxy phosp halt

Noted tissue po2 normal or elveated - impar oxy utilasation

Opp other forms
prime cause decerased o2 cell is decrease oxygen
Doent fit defn
revised

Oxygen substrat cyto oxidase
enz end etcp
All tissue effects of hypoxia - lack avial energy form atp block ox phosphrylaton

new defn

hpyoxia oxidative phosprhylation stops d/t inadeq utilisation of oxygen
crtil low cell po2 1-2mmHg

level pasetru point
very high oxygen affin for xyto oxidase
rxn continue until nearly all o2 gone

histotox hypica - ox phosp block - orimary effect on ETC

Question 47

What phsyiological effect walk into room 100% N2 - close door

Answer 47

Hypoxaemia & anoxic hypxia
cyanosed
distressed death min

initial affect art po2 drop - no oxygen in inspired gas
po2 <50mmhg - peripher chemo repsond - vent progres increase
increase washout of o2 lung
frc major store

other effect

cerbral hypoxia - brain tisue lac admosis
central chemo respond to stim resp centre

cerenbgral hpyoxia - depression brai unconcuouss death

circ effect
autoreg - vasil near all tiuse increease flow vr and co
vasocn - cerbral - overom hypocapnioa cbf incrase

Carotid ody stim - severe brady - hypoxic brady
increase RR - increase Symp stim - increase hr - masks direct brady

HPV - rise in PApressure

cerebral hypox - symp stim - rise arterial bp - cushing reflex

Hypoxia - results depresion metaboims all cell

high oxgen affinity cyto oxidase - mito ox phospho contin down to po2 of 1 - pasteru

muscle internal small oxygen store omyoglobin

many tissues can derive additonal energy anearobi meatob 0 intracell acidosis

brain tissue most suecctile hypox and anox brain - coma death minutes

Question 48

Shunt

What is the venous admixture

Answer 48

Term intechange shunt

shunt - blood enter aterial system wihtout passing thru ventilated area lung
ture shunt
po2 blood diff po2 mix venous blood
most cases po2 true shunt lower po2 blood - contrib depress art po2

Venous admix - amount mix venous blod added to pulm end capillary blood - produce obesreved drop art po2 from po2 in end capillary

n

Question 49

Normally healthy peorosn two main source blood

Answer 49

contribu venous admix - blood true shunt
bronch benous blood - bronch circ
blood thebesida - blood not mix venous blood not expect po2 same mix venous

blood alveoli v/q <1
blood not fully oxygntead - passes poorly vent area lung
not true shunt - passed some ventilation
really v/q mm

Question 50

Virtual shunt

Answer 50

Blood source - drop art po2
neither venous mdmix mixed venous blood

amt venous admix calc shunt eqn
value obtain

• lable virtual shunt
  defined amount shunt present if shunt enitrely mix venous blood
  amt shunt fully accoutn drop art oxygen content

advantage 
estimate venous admix obtain - monitor patient
clin usefu
no easy way calc true shunt 
no alternat use virtual shunt

noted smome case ssunt will bbe mix venous blood
mix ven blood shunt are lung not veniltaed
this case venous admix - shunt will be same

Question 51

How can shunt eqn be calulatied

Answer 51

Qs/Qt = (CC’O2 - CaO2)/(CC’O2-CvO2)

eqn calc amt shunt of mix venous blood

Actual blood shunt may diff comp
value - not accurate in these esitn

normal sitation
shunt present bronchial circulation
thebesian vessel - lv compositon diff mix venous blood

Summary

shunt eqn based assumption
shunted blood has same com as mix venous blood
gives measure amt mix venous blood if added to end cap blood produce observed epression in art Po2 - virtual or as if shunt - true shunt not measure by eqn

Question 52

How is shunt eqn derived

Answer 52

Bloods that shunt mix venous blood

CO Qt
= sum of shunt blood flow Qs +
blood flow thru lung Qt-Qs

total oxygen delivery - to body is CO by art content
Qt x CaO2
Must be equal sum of oxygen deliver from shunt and lung
Hence
Qt xCao2 = Qs CCvO2 + Qt-Qs X CCo2

Solvng yields shield eqn

Draw page 155

must equal sum amt oxygen dleivery shunt from lung
diagr page 155

Question 53

PVR

How does vascular resitance in Pulmonary circulation compare to systemic

Answer 53

General ft Pulm - low resistance circuit
Pressure drop only 10mMhg - mean PA - 15 Mean LAP 5

Yet flow is same as systemic circuit - ie Whole Cardiac output

Pul VR 1/10th SVR
AS pressure drop in SVR 100 - 10x higher

Question 54

What are major factors affecting PVR

Answer 54

1 Hypoxic pulmonary vascon
2 Lung volume
3 PA Pressure

Question 55

What is HPV

Answer 55

Vasoconstrictive low alveolar Po2 -

Alveolar Po2 - determins not art Po2

When Po2 falls in one part lung = decrease vent or atelac w/ mucus pplug - pulmonary vassels vasoconstrict -
shunt pulmonary blood away - underdentialted area - better vent areas lung

Match vent and perfusion
advantrage - maint o2 uptake

During early LVF _ congest and hypxia - cause hpv shunt to upper zone - pulmonary vascular redistrib

Question 56

What circ HPV - interest anaetheitst

Answer 56

Effect volatile

One lung anaesthsia

Question 57

Relationsip PVR and lung volume

Answer 57

High and low lung vol - PVR increase

PVR lowest - when lung vole close to FRC

Low lung vol - extra alveolar vessels - small diamter high resistance

as volume expands - wall pulled by elastic fibre in lung - and diameter increase
resistance decreases

As volume expands further
increased stretching distort and decrease diam of pum capillary - alveolar vessels - causes increase PVR

PVR higher at high and low lung vol - d/t different meachansms

PVR is at FRC

Question 58

how does PAP pressure affect PVR

Answer 58

Increase PA pressure signif decrease PVR

Remark prop - how low PVR already

Recruitment and dsitension of pulm capil

Question 59

What are measure required to calculate PVR using swan

Answer 59

PVR = MEAN PAP =PCWP x 80
____________________
CO

Vas resistance = input P - output P/ blood flow

Normal value 100 dynes sec

Question 60

West zones

Answer 60

Zone 1: PA > Pa > Pv
MAy be present at top - if drop in BP - Inc PA - 2’ to IPPV - alveolar dead space

Zone 2: Pa > PA > Pv
Blow flow det diff b/w art & alveolar pressure - stralring resist mech - pulsatile

Zone 3: Pa > Pv > PA
FLow determ AV diffce
Distenion

Zone 4: Pa > Pi > Pv > PA

alveoli (PA), in the arteries (Pa), in the veins (Pv) and the pulmonary interstitial pressure (Pi) :