Summary Mechanisms of Arterial Hypoxemia

Mechanisms of Arterial Hypoxemia




Pat =
Alveolar POz Hypoxia @ doesn't reach the tissues
=
PUL 54. Explain wh
subatmospheric and
Pa02 = arterial PO ↳
Hypoxemia there is no 0 within the =
blood; it is
breathing 100%02.
or closure form of . further arterial 02 d
atelectasis collapse =
a
hypoxia mucous plugging of
of part of the lung resulting in
·
the mechanism of hypoxemia consists of multiple factory
.

reducedorabtentairexchanglead. incl .
V/Q mismatching, ReL shunt, or diffusion impairments
. Venous Blood is
s
ARDS acute distress blood suba
respiratory venous is
· = ·




PUL 42. Be able to calculate the alveolar to arterial P02 difference, (A-a)
syndrome that causes
hypoxemia .




D02. Describe the normal value for (A-a) D02 and the significance of an
dissolved gases It .




fluid builds up inside the tiny air elevated (A-a) D02. but overall Previo

says of the
lungs and surfactant
·
The A-a
gradient is the difference btwn he alveolar and ·
when a
person
breaks down arterial PO A normal gradient suggests normal gas exchange
. in their
lungs be
.




btwn alveoli and blood
. Help us determine if further reductio
hypoxemia may be present. NOTE
=
accentuating th
A -

a
gradient
=
PaO2-PaO · The normal
gradient for
- a nonsmoker is 5-10 mutty
Absorption Atele
PADEtx(Patm-PH20) (
-
·
The gradient by , -3
mmtg
for each decade >30y10 Breathing 100 % O
·

.




medi
I
·
An increase in age ↓ gas
=> if there is a mucus
Inspired 02
exchange due to
aging alveoli washout can exa
(VPaOc)
- absorption atelec
1. ventilation -

Perfusion (v/Q) PUL 43. Name five causes of hypoxemia. · In ab
Definition supplemental of Helpful
Mismatch CAUSES OF HYPOXEMIA
a
-
Examples
niroge
ARDS 102 want help)
Pulmonary en
·
-




·




a ShunngRshunt
Asthma Fibrosis
O co
·




conditions when PaOz is lower
·
Pneumonia
· COPD ·


pulmonary
Hypoxic Hypoxia than normal . 1 .
e diffusion Y ES ·

emphysema edema
desat
on
impairment (v/Qmismatch) ·


·
Pneumothorax
Medications that
sleep apnea
breathing
.
2 Impairment Diffusion · Interstitial lung disease
in pat
. Decreased Inspired o (high NOT TOO HELPFUL;
pluggi
-




3 ·
decreate Of Content ((a02) While anemia
Hypoxia
·

Anemit ONLY INCREMENTALLY
PaO2 and PAOc are normal
altitude) heart defects
·
The pl
Congenital
(V/ Q mismatch)
·




Hypoperfusion Hypoxia- low blood flow ONLY INCREMENTALLY in children + adults
HELPFUL ·
Pulmonary embolism gradu
Historixit Hypoxia ·
cellular poisoning ; CaO2 , PAO2 and LITTLE HELP co monoxide
-
leadin
PaO2 all NORMAL poisoning and fu

Hypoxic Hypoxia via Diffusion Impairment compensat
Low
of
there is mild reduction 1 .




i



FI
in Pa02 compared to
- - ① ,

NOTE :
normal
.
2
Hig
·
with diffusion it takes
impaired
longer for the blood to reach
⑳ excercise
w/ alveoli
equilibrium wh
w/ extreme = NORMAL ·
at faster blood speeds such as
- impaired diffusion Imp AIRED
Absorptio
-
ul excercise the blood will be
severely
-




L
there is
significant hypoxemia
hypoxemic
①




·T·
w/extreme ·
impaired closer to diffusion tur
excercise the limited
I RBL spends a


Hypoxi
-



short amount of ·
at rest
time wli the pulm
capillary
.
-
L
when traveling
normal speed
RBC is
.
v/Q m
I at ·


O 0 25 . 0 5 .

0 75 .




Hypo
·
Time RBC spends in pulmonary capillary (S)
·

R-1 S

v/Q mismatching

points of v/Q mismatch -
3

wasted
Ventilation
V/Q ratio NOTE
&

2
&

=



I
-




When
·
i Q then there is a

wasted Va mismatch
perfusion the Ideal v/Q 1 but not possible
=

I
·
-


he middle
typically v/a 0 8 around
= .




7 oft he
lung (Zone 2)
Base Is LapeX
.




·the APEX receives little perfusion

compared to perfusion
: v/Q =***
D RIB NUMBER CZONE1)
Q ·
Ne BASE receives
comparatively less
&= perfusion ventilation to perfusion (ZONE 3)

via
=
XV


j v = ventilation