Mechanics Of Ventilation

Front 1

elasticity of lung

Back 1

tendency to recoil inward and pull away from the chest wall.
generated by 1) elastic and collagen fiber of the lung parenchyma and 2) surface0-tension forces of the thin liquid film lining the alveoli.

Front 2

elasticity of thorax

Back 2

tendency to recoil outward, away from the lung

Front 3

pressure between lung and chest wall

Back 3

is negative. decreases as the lung and chest wall recoil in opposite directions (boyles law).

Front 4

alveolar pressure

Back 4

negative during inspiration.
0 when no airflow.
positive during expiration.
equal to Ppl +alveolar elastic recoil pressure.

Front 5

transpulmonary pressure

Back 5

difference btwn alveolar and intrapleural pressures.
the distending pressure across the alveolar walls.

Front 6

rib cage movement

Back 6

change anterior-posterior and lateral dimensions of the thorax.

Front 7

diaphragm movement

Back 7

displace the abdominal organs and change the vertical thoracic dimensions

Front 8

residual volume

Back 8

cannot be exhaled because rigid rib cage prevents total lung deflation.
1200ml

Front 9

tidal volume

Back 9

air inhaled with each breath.
500ml

Front 10

expiratory reserve volume

Back 10

abdominal muscles must contract to exhale this air.
1100ml

Front 11

total lung capacity

Back 11

amount of gas the lung contains after a maximal inspiratory effort

Front 12

inspiratory reserve volume

Back 12

air that can be inhaled with maximal effort from the tidal end-inspiratory level.
3000ml

Front 13

frc

Back 13

rv + erv
air in the lungs at the point of ventilatory muscle relaxation. about 40% of the tlc.

Front 14

ic

Back 14

air that can be inhaled with maximal effort from a resting end-expiratory level.
Vt + IRV

Front 15

VC

Back 15

maximum vol of air that can be exhaled after a max effort inspiration.
irv + Vt + erv

Front 16

MEP

Back 16

greatest at TLC.
bad if less than 40cmH2O

Front 17

MIP

Back 17

greatest at RV.
often used to assess ability to maintain unassisted ventilation. bad if not more that -25cmH2O can be generated

Front 18

hysteresis

Back 18

at same pressure, lung volume is greater during deflation than inflation.
due to energy needed to recruit alveoli during inspiration.

Front 19

LIP

Back 19

lower inflection point.
accelerated recruitment rate, steeper slope on the P-V curve

Front 20

compliance

Back 20

opposition to inflation.
change in V/change in P.
shift to left (emphysema)
shift to right (fibrosis).

Front 21

LaPlace's law

Back 21

P=2T/r
small alveoli require highre destending pressure than large alveoli

Front 22

surfactant

Back 22

alters alveolar surface tension so that larger have a higher surface tension than smaller alveoli.
Makes recoil pressure resulting from surface tension the same for all alveoli.

Front 23

critical opening/closing pressure

Back 23

pressure to produce an alveolar radius equal to that of the alveolar duct supplying it. Takes a lot of pressure, but then it expands easily.
Depends of the radius of the duct and the surface-tension force.

Front 24

surfactant composition

Back 24

90% phospholipid and 10% protein.
DPPC is 50% of the phospholipid.

Front 25

resistance to gas flow

Back 25

=(P1-P2)/flow
normal is 0.5-1.5cmH2O/L/sec

Front 26

laminar flow

Back 26

pressure required to produce a given flow rate is influenced by gas viscosity

Front 27

Poiseuille's law

Back 27

under laminar flow conditions, the pressure req'd to produce a given flow rate is defined by Poiseuille's law.
P=flow8length*viscosity/pi(r4)

Front 28

turbulent flow

Back 28

pressure gradient proportional to flow rate.
dependent on molecular weight/density of gas

Front 29

how to calculate static compliance

Back 29

on mechanical vent, stop air flow and hold breath until all airflow ceases.
peak=elastic recoil force + frictional airways resistance.
plateau=elastic recoil force

Front 30

calculating compliance on mech vent

Back 30

C=Vt/(Pplat-baseline pressure)

Front 31

calculating Raw on mech vent

Back 31

Raw=(Ppeak-Pplat)/inspiratory flow

Front 32

equation of motion

Back 32

Pmus + Pvent=(V*E) + (flow * Raw)

Front 33

cephalad flow bias

Back 33

during expiration, transpulmonary pressure decreases, causing the airway diameter to decrease. smaller airway decrease more (less cartilage), so flow it picks up speed and pushes mucus out.

Front 34

time constant

Back 34

TC=Compliance * Raw
five TC's to achieve inhalation or exhale all the air

Front 35

pendelluft

Back 35

due to high airway resistance, alveoli develop differential pressures at end-inspiration. after inspiration ceases, air continues to flow w/in the lung from hi to low pressure areas.

Front 36

closing volume

Back 36

person exhales a inspired VC of 100% O2. as exhalation approaches RV, small basal airways close and no longer contribute their nitrogen-depleted air. Near RV, exhaled gas comes entirely from nitrogen rich apical alveoli. the basal airway closure point marked by sudden increase in exhaled nitrogen concentration. this volume - RV is closing volume.