Respiratory Physiology and Spirometry

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24 Οκτ 2013 (πριν από 3 χρόνια και 10 μήνες)

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Respiratory Physiology and
Spirometry

Spirometry


Nml

Values:


TV 6
-
10cc/kg, VC 60
-
70cc/kg, dead space 2cc/kg


Conditions:


Aging:


incr

rv,frc
, cv.


decr

vc

tlc
, fev1


Pregnancy:


Incr

tv



Decr

rv
,
dec

frc
,
dec

tlc


No change:
vc
, cc


Morbid Obesity


Decr
:
erv
,
frc
,
vc
,
tlc

and cc


No change:
rv
,
tv



High Spinal Cord Injury


Decr
:
erv
,
tv
,
frc
,
vc
,
tlc


Scoliosis


Depends on angle: >65
degr

restric

pattern


Decr
:
greates

is
vc
,
frc
,
tlc



Male
vs

female


Females have 10% smaller
frc


Supine
vs

Upright


Supine worse


Emphysema:


Incr

FRC


PEEP:


Incr

frc



Closing Capacity


Closing Capacity:


Closing
vol
: the volume of gas at which
small airways w/o
cartiledge

collapse,
esp

w expiration from positive
intrapleural

pressure.


When small airways close, you “air trap”


Closing cap:
rv

+ closing volume


AGE:


Closing volume
incr

c age. So we
shunt more with age and hence
why our p art O2 is lower with age
(102
-
age/3).


At 44, cc =
frc

supine


At 66, cc=
frc

upright


Closing cap in NOT affected by posture.
Only
intrapleural

pressure affects it.


Other factors which increase CC “
acls

so”


Age


COPD: asthma, emphysema,
Chronic bronchitis


Lv

failure (pleural effusion, wet
lungs)


Surgery


Smoking


Obesity (
contraversial
)


Lowest closing capacity is in teens


Measures with xenon
-
133 tracer gas.



Questions about West Zones




Dead space?


Zone 1



Shunt?


Zone 3



most
Ventillated

zone awake? Does General
Anesth

change this?


Zone 3 goes to zone 1 b/c
diaghram

push loss of HVC



Compliance Greatest in zone? Because of
what?


Zone 3 b/c conc. surfactant



Most
perfused

zone?


Zone 3 gravity



Alveoli are larger and more distended in
zone?


Zone 1 more
neg

intrapleural

pressure


Do the zones change standing
vs

supine
vs

prone?


Standing: only position with zone 4.


supine, the zones still exist top to
bottom.


Z1 anterior, Z2 middle, and zone 3
posterior (supine).


Prone: Z1 posterior, Z2
-

middle, Z3
anterior.




















Which zone varies the most with the Cardiac
cycle?


Zone 2: Has intermittent blood flow
--
during systole,
pulm

capillary pressure is
greater than alveolar pressure. During
diastole,
pulm

capillary pressure is less
than alveolar pressure.



Pulmonary Edema Causes larger zone?


Zone 4



What zone should a pa catheter lye in?


Zone 3



What happens in pregnancy?


Zone 1 becomes smaller



What happens with
ionotropes
?


Zone 1 becomes smaller



Every 20cm of length, causes a difference in
pressure from top to bottom of __mmHg.


15mmHg


Which zone does not exist at rest? What causes
this zone to exist?


Zone 1



Which rib has the best V/Q matching?


Rib 3




Surface Tension and Alveoli


Laplace Equation= P=2T / r
T = surface
tension r = radius of alveolus

Surfactant:


lipoprotein produced by type II
pneumocytes



Mitigates surface tension in alveoli preventing
their collapse.


Which alveoli are more likely to collapse?


During which phase of
ventillation

will collapse occur?


as alveolar size decreases, surface tension increases.


Smaller alveoli have more surfactant/unit area.


Prevention of
Pulm

edema: Surface tension
forces also draw fluid from capillaries to the
alveolar spaces. Surfactant by reducing these
forces keeps the airways dry.


ARDS= Lack of surfactant, more
atelectasis
,
v/q mismatch.


Aspiration: kills type 2
pneumocytes


Oxygen toxicity: kills type 2
pneumocytes

after 12 hours.

Pulmonary Mechanics:

Pulmonary compliance is split
into two parts:

1.
Dynamic lung compliance:


The pressure for air flow
and airway resistance to
flow


PEAK
Inspiratory

pressure

2.
Static lung compliance:


The pressure at end
inspiration with zero gas
flow


PLATAE pressure.

Pulmonary Mechanics


DDx

of Increased Peak Airway Pressure,
Nml

Platae
:


Problem with airway resistance to gas flow


Upper airway problems: posterior displacement of the tongue


ETT problems: Kinked tube,
mucuos

plug,


Trachea: secretions,
laryngospasm
, blood, tumor,


Bronchial tree: bucking vent/lack of paralysis,
bronchspasm
,


equipment problems: small ETT,
malfunc

valve, obstruction of the breathing
circuit, Foreign bodies,


Turbulent gas flow (use helium to temporize)


Reynolds number of >2000 is turbulent and depends on density



DDx

of High Peak with High
Platae

pressures


Platae

pressure is looking only at lung/chest wall compliance, with zero gas flow and
therefore, airway resistance contribution.


Only lung and chest wall compliance are factors:


High tidal volumes,
endobronchial

intubation,
trendellenberg
, breath stacking c
air trapping from insufficient expiratory times (
esp

c
copd

pts
)PNEUMOTHORAX, ARDS,
hemothorax,,pulmonary

edema, effusion,
ascites
,
abd

packing.

abdominal distention,).


Question 1


A 67 y/o 55 kg female with 45 year pack history of tobacco use, was in an
mva

vs. pedestrian (pt was pedestrian) and thrown 10 feet. On arrival in
the operating room, she comes
intubated
, with multiple abrasions, seat
belt sign and bilateral pelvic fractures. Her
vs

are as follows: hr125,
bp

90/60, sat 89%. You place her on the
ventillator
,
paralize

her, set her in
mild
trendellenburg

and set the
ventillator

to
tv

675,
rr

8, fio2 100%. 5
minutes into your arterial line placement, the high airway pressure alarm
alerts, with Peak pressures of 35 and
plateu

pressures of 25 with
increasing tachycardia. Breath sounds are distant bilaterally. The next
best step in the management of this patient is:


a/ increase the amount of paralysis.


b/ needle
thoracoscopy

followed by a chest tube.


c/change the
ett

to a larger size.


d/ decrease the tidal volume.


e/suction the airway.

Question 2


All of the following conditions predispose to
hypoxia on induction except:


a/ obesity


b/ pregnancy


c/ asthma


d/ old age


e/ asbestos exposure for twenty years.

Question 3


Two days after CABG, a 62 year old man remains sedated,
intubated

with full neuromuscular blockade. Over the next
three hours, Pao2 decreases from 90 to70 mmHg at an FIo2
of 0.7, peak
inspiratory

pressure measured proximally in
the
ventilatory

circuit increases from 40
-
66cm H2O, and
plateu

pressures remain unchanged at 30 cm H2O. Which
of the following is the most likely cause of these changes?


a/ ARDS


b/Bronchial mucus plugging


c/left ventricular failure


d/lobar pneumonia


e/ tension
pneumothorax