mechanics

Question 1

compliance

Answer 1

tendency to distort under pressure

change in V/change in P

Question 2

elastance

Answer 2

tendency to recoil to original vol
retain its shape
change in P/change in V

Question 3

COPD and compliance

Answer 3

more compliant

recoil forces don’t exist

Question 4

Fluid filled lungs and compliance

Answer 4

same volume changes as air filled lungs
more compliant
start stretching immediately - water:water interface provides surface tension
from forces holding water together

Question 5

alveoli without surfactant

Answer 5

a lot of force to bring air in
upward pressure from water - collapsing the lung
small airwasy collapse - force air into larger airways

Question 6

alveoli with surfactant

Answer 6

surfactant break up tension - phospholipid

easier to ventilate

Question 7

surfactant

Answer 7

made by Type 2 pneumocytes 
reduce collapsing pressure 
80% polar phospholipids 
10% non-polar lipids 
10% protein 
increases compliance by reducing surface tension

Question 8

law of Laplace

Answer 8

tension proportional to the radius

not linear

Question 9

resistance through the generations

Answer 9

R inversely proportional to 4th power of the radius
reduces velocity - air not even moving in small airways
however exponential increase in cross sectional area from 7th generation - hydrostatic pressure decreases

Question 10

conductance

Answer 10

how much conductancy airways offer
increases as lung vol increases
airways distorted under pressure

Question 11

COPD resistance

Answer 11

increase
bronchoconstriction
excess mucous
bronchitis

Question 12

ventilating with a snorkel

Answer 12

ventilation more forceful

against the dead space

Question 13

effect of using a larger snorkel

Answer 13

breath the same air so deplete O2 and increase CO2 - breath faster - exacerbrate situation - die
deeper - increased hydrostatic pressure - resp muscles work harder to expand
poiseuille’s law - importance of radius for pressure
Boyle’s law - pressure is inversely proportional to volume
more effort to breathe

Question 14

poiseulle’s law

Answer 14

R = 8nl/pi(r)to power of four

Question 15

boyle’s law

Answer 15

Pgas (proportion symbol) 1/Vgas

Question 16

mechanics of ventilation

Answer 16

as volume increases or decreases in lung - more pressure is needed to expel or inhale even more - huge effort to be ventilated
in expiration - low externally applied pressure, push pleura togeteher = increase in pleural pressure to -2
in inspiration- high externally applied pressure, pill pleura apart = pleural pressure decrease

Question 17

volume and pressure relationship in COPD

Answer 17

height:width of curve change - lung more compliant - less pressure needed to change vol

Question 18

vol and pressure relationship in restrictive lung

Answer 18

vital capacity reduced

stretch more - more effort to move in - wall less compliant

Question 19

relationship between flow rate Palv, vol and Ppl

Answer 19

subtract vol from Ppl = curve for Palv and flow

Question 20

Flow in collapsible tubes

Answer 20

pre-inspiration: no flow - func residual capacity - pleural pressure -2 because of recoil chest oppsoinbg force = partial vol
mid insp - decrease pressure in pl to -8, -2 in airway - transmural pressure +ve so airway open
end insp - airway pressue 0 - transmural still +ve (0–8)
hard expiration - pleural increase to +22 transmural pressure -ve (airway pressure 20) - would collapse but have cartilage support

Question 21

mechanical forces in tidal vol

Answer 21

functional residual capacity at start
want to draw air in - use insp muscles
open lung
reduce pressure
create vacuum in lungs - pressure gradient - air in
pressures balance - atm 0cm H2O = no gradient
recoil of lung compress air - push it out
net change in vol is reversed

Question 22

mechanical relationship with the chest wall

Answer 22

chest wall tendancy to spring out
lung tendency to spring in
these forces are in equilibrium at end tidal expiration - func residual capacity
neutral position of the intact chest
chest wall and lungs single unit
have own combination of physical properties - together dictate position, characteristics and behaviour of intact wall

Question 23

chest wall and inspiration/expiration

Answer 23

in inspiration: insp muscle and chest recoil > lung recoil

expiration: chest recoil

Question 24

Pleura

Answer 24

visceral pleura - on lungs
parietal - on chest wall
pleural cavity - gap with fixed vol, contains protein rich pleural fluid
lubricated movement - allow 2 things to work against each other

Question 25

things that affect the pleural cavity

Answer 25

interpleural bleeding - compress lung, harder to expand

puncture - air in space - alter ability for lung and wall to be a single unit

Question 26

-ve pressure breathing

Answer 26

Palv

Question 27

+ve pressure breathing

Answer 27

Patm>Palv
ventilator
mouth to mouth
fighter piolet - cant generate -ve pressure

Question 28

transmural pressure

Answer 28

pressure across tissue
always Pinside-Poutside
-ve trans resp pressure = insp
+ve transresp pressure = expiration

Question 29

pleural pressure

Answer 29

-ve
not constant across lung
from lung pulling in and wall pulling out

Question 30

Transpulmonary pressure

Answer 30

between alveoli and interpleural space

Question 31

transthoracic

Answer 31

between interpleural space and atm

Question 32

transrespiratory

Answer 32

between alveoli and atm

determines air flow

Question 33

muscles in ventilation

Answer 33

diaphragm - contract and move down - increase vol - air in
intercostals - move ribs like bucket handle
quiet breathing just use diaphragm

Question 34

graphical relationship between pressure and vol

Answer 34

intact lung - sigmoid shape
vol change per unit of pressure
have to supply greater pressure at extremes to change vol and so airflow

Question 35

intrapleural pressure at start of insp

Answer 35

muscles pull parietal away from lung 
stretches interpleural space 
lung truying to recoil in 
visceral pleura pulled in 
increasing the partial vacuum 
pressure decrease

Question 36

calculating alveolar vent

Answer 36

breathing freq per min*(tidal vol-physiological dead space)